how to fix a blown preamp pedal ?

[Jack Jarmush]

Hi,
I fried a Behringer preamp pedal (PB100) by using the wrong polarity
from a 12v battery. The preamp pedal accepts negative polarity but my
battery plug is positive .. D'oh!
Do you think it's fixable ?
-JJ

[Scott Dorsey]

Jack Jarmush > wrote:
>Hi,
>I fried a Behringer preamp pedal (PB100) by using the wrong polarity
>from a 12v battery. The preamp pedal accepts negative polarity but my
>battery plug is positive .. D'oh!
>Do you think it's fixable ?
>-JJ

Maybe. The problems start, though, with getting a schematic from
Behringer and tracing through it and seeing what the possible failures
are. If there's a protection diode, it's gone, and if there isn't
whatever electrolytics are on the incoming line are gone. Trace downstream
from there. It might not be that big a deal.

This stuff is very cheaply made and it's intended to be disposable, which
can be a problem. But don't give up.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Gareth Magennis]

"Jack Jarmush" > wrote in message
...
> Hi,
> I fried a Behringer preamp pedal (PB100) by using the wrong polarity
> from a 12v battery. The preamp pedal accepts negative polarity but my
> battery plug is positive .. D'oh!
> Do you think it's fixable ?
> -JJ


Yes. I don't know this particular pedal, but many such devices use a single
diode wired in reverse for polarity protection. If you use the wrong
polarity power supply, this diode shorts out the incoming voltage, and burns
to a short circuit, thus protecting the pedal, but sometimes breaking the
power supply instead.

In many cases you can simply replace this diode and the pedal will work
again.
Find someone who can identify and replace a shorted diode without damaging
the circuit board. A plumber, drummer, or motor mechanic are probably best
avoided.




Gareth.

[Jack Jarmush]

On Jan 5, 12:34*am, "Gareth Magennis" >
wrote:
> "Jack Jarmush" > wrote in message
>
> ...
>
> > Hi,
> > I fried a Behringer preamp pedal (PB100) by using the wrong polarity
> > from a 12v battery. The preamp pedal accepts negative polarity but my
> > battery plug is positive .. D'oh!
> > Do you think it's fixable ?
> > -JJ
>
> Yes. *I don't know this particular pedal, but many such devices use a single
> diode wired in reverse for polarity protection. *If you use the wrong
> polarity power supply, this diode shorts out the incoming voltage, and burns
> to a short circuit, thus protecting the pedal, but sometimes breaking the
> power supply instead.
>
> In many cases you can simply replace this diode and the pedal will work
> again.
> Find someone who can identify and replace a shorted diode without damaging
> the circuit board. *A plumber, drummer, or motor mechanic are probably best
> avoided.
>
> Gareth.

Thanks Scott and Gareth, I'll email Behringer to try and get a
shcematic and if i can't get that i'll take it over to a friend
(guitarist, not drummer lol) who may be able to find the short. cheers
-JJ

[Bill Graham]

Jack Jarmush wrote:
> Hi,
> I fried a Behringer preamp pedal (PB100) by using the wrong polarity
> from a 12v battery. The preamp pedal accepts negative polarity but my
> battery plug is positive .. D'oh!
> Do you think it's fixable ?
> -JJ

Yes. But when you do, put in a full wave bridge (4 diodes) so that it can
never happen again.

[Mike Rivers]

On 1/4/2011 5:35 PM, Jack Jarmush wrote:

> Do you think it's fixable ?

Everything's fixable, but if you're hoping to fix it
yourself, the fact that you haven't already taken it apart
and checked a few things out suggests that you won't. It's
probably not worth paying for a repair. I don't suppose it's
still within the warranty period. They say they'll replace
anything in warranty that's broken no matter what happened
to it.

--
"Today's production equipment is IT based and cannot be
operated without a passing knowledge of computing, although
it seems that it can be operated without a passing knowledge
of audio." - John Watkinson

http://mikeriversaudio.wordpress.com - useful and
interesting audio stuff

[timewarp2008]

On Jan 4, 8:16*pm, Mike Rivers > wrote:
> On 1/4/2011 5:35 PM, Jack Jarmush wrote:
>
> > Do you think it's fixable ?
>
> Everything's fixable, but if you're hoping to fix it
> yourself, the fact that you haven't already taken it apart
> and checked a few things out suggests that you won't. It's
> probably not worth paying for a repair. I don't suppose it's
> still within the warranty period. They say they'll replace
> anything in warranty that's broken no matter what happened
> to it.
>
> --
> "Today's production equipment is IT based and cannot be
> operated without a passing knowledge of computing, although
> it seems that it can be operated without a passing knowledge
> of audio." - John Watkinson
>
> http://mikeriversaudio.wordpress.com- useful and
> interesting audio stuff

[timewarp2008]

On Jan 4, 8:11*pm, "Bill Graham" > wrote:
> Jack Jarmush wrote:
> > Hi,
> > I fried a Behringer preamp pedal (PB100) by using the wrong polarity
> > from a 12v battery. The preamp pedal accepts negative polarity but my
> > battery plug is positive .. D'oh!
> > Do you think it's fixable ?
> > -JJ
>
> Yes. But when you do, put in a full wave bridge (4 diodes) so that it can
> never happen again.

Billy, can you tell the difference between a stock PB100 and a PB100
with a full-wave bridge, in a double-blind listening test? Then why do
you think it's worth the extra time and money? Hmmmmmm?

[Scott Dorsey]

timewarp2008 > wrote:
>On Jan 4, 8:11=A0pm, "Bill Graham" > wrote:
>> Jack Jarmush wrote:
>> > Hi,
>> > I fried a Behringer preamp pedal (PB100) by using the wrong polarity
>> > from a 12v battery. The preamp pedal accepts negative polarity but my
>> > battery plug is positive .. D'oh!
>> > Do you think it's fixable ?
>> > -JJ
>>
>> Yes. But when you do, put in a full wave bridge (4 diodes) so that it can
>> never happen again.
>
>Billy, can you tell the difference between a stock PB100 and a PB100
>with a full-wave bridge, in a double-blind listening test? Then why do
>you think it's worth the extra time and money? Hmmmmmm?

Sadly, you probably CAN tell the difference, due to the 1.2V drop of the
full wave bridge. When you're running on a 9V battery, a 1.2V drop is
significant.

If you DO go the bridge route, at least use schottkys. But the real
solution is just to be careful.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Doug McDonald[_4_]]

On 1/5/2011 9:35 AM, Scott Dorsey wrote:
> > wrote:
>> On Jan 4, 8:11=A0pm, "Bill > wrote:
>>> Jack Jarmush wrote:
>>>> Hi,
>>>> I fried a Behringer preamp pedal (PB100) by using the wrong polarity
>>>> from a 12v battery. The preamp pedal accepts negative polarity but my
>>>> battery plug is positive .. D'oh!
>>>> Do you think it's fixable ?
>>>> -JJ
>>>
>>> Yes. But when you do, put in a full wave bridge (4 diodes) so that it can
>>> never happen again.

Why a bridge? Why not just one diode? If you connect the wrong polarity,
it just won't work, and you lose only one diode drop.

Doug McDonald

[Gareth Magennis]

"Jack Jarmush" > wrote in message
...
> On Jan 5, 12:34 am, "Gareth Magennis" >
> wrote:
>> "Jack Jarmush" > wrote in message
>>
>> ...
>>
>> > Hi,
>> > I fried a Behringer preamp pedal (PB100) by using the wrong polarity
>> > from a 12v battery. The preamp pedal accepts negative polarity but my
>> > battery plug is positive .. D'oh!
>> > Do you think it's fixable ?
>> > -JJ
>>
>> Yes. I don't know this particular pedal, but many such devices use a
>> single
>> diode wired in reverse for polarity protection. If you use the wrong
>> polarity power supply, this diode shorts out the incoming voltage, and
>> burns
>> to a short circuit, thus protecting the pedal, but sometimes breaking the
>> power supply instead.
>>
>> In many cases you can simply replace this diode and the pedal will work
>> again.
>> Find someone who can identify and replace a shorted diode without
>> damaging
>> the circuit board. A plumber, drummer, or motor mechanic are probably
>> best
>> avoided.
>>
>> Gareth.
>
> Thanks Scott and Gareth, I'll email Behringer to try and get a
> shcematic and if i can't get that i'll take it over to a friend
> (guitarist, not drummer lol) who may be able to find the short. cheers
> -JJ


You won't get any service info from Behringer.

You probably don't need any anyway - if it can't be fixed easily without a
schematic it is properly fried.



Gareth.

[Kevin Aylward[_4_]]

"Scott Dorsey" wrote in message ...

timewarp2008 >> wrote:
>>On Jan 4, 8:11=A0pm, "Bill Graham" >> wrote:
>>>> Jack Jarmush wrote:
>>>> >> Hi,
>>>> >> I fried a Behringer preamp pedal (PB100) by using the wrong polarity
>>>> >> from a 12v battery. The preamp pedal accepts negative polarity but
>>>> >> my
>>>> >> battery plug is positive .. D'oh!
>>>> >> Do you think it's fixable ?
>>>> >> -JJ
>>>>
>>>> Yes. But when you do, put in a full wave bridge (4 diodes) so that it
>>>> can
>>>> never happen again.
>>
>>Billy, can you tell the difference between a stock PB100 and a PB100
>>with a full-wave bridge, in a double-blind listening test?
>Then why do
>>you think it's worth the extra time and money? Hmmmmmm?

>Sadly, you probably CAN tell the difference,

Depends what you mean. You will lose headroom, so things might clip earlier,
but other than sort of thing there should be no audible difference at all if
it been designed competently. Some battery pedals will have an internal
regulator, if not, the design would be relying on the typical 80db-110db
L.F. power supply rejection of the op-amps, and some RC filtering for HF.



Kevin Aylward B.Sc.
www.kevinaylward.co.uk
"Live Long And Prosper \V/"

[Kevin Aylward[_4_]]

"Scott Dorsey" wrote in message ...
>Billy, can you tell the difference between a stock PB100 and a PB100
>with a full-wave bridge, in a double-blind listening test? Then why do
>you think it's worth the extra time and money? Hmmmmmm?

>Sadly, you probably CAN tell the difference, due to the 1.2V drop of the
>full wave bridge. When you're running on a 9V battery, a 1.2V drop is
>significant.

>If you DO go the bridge route, at least use schottkys. But the real
>solution is just to be careful.

This is a well known problem with a solution that can reduce the volt drop.
I have not checked what is actually off the shelf today, but an example of
the principle is the MAX4636 from Maximum.

MAX4636

http://www.maxim-ic.com/app-notes/index.mvp/id/480

This device is for below 5V and for lower currents, but I am quite familiar
with the technique so if anyone is interested I could knock up a circuit
using bigger discrete mosfets and post it.

Maximum or others e.g. Linear Technology may already have have something,
but I don't have time to check right now.

Kevin Aylward B.Sc.
www.kevinaylward.co.uk
"Live Long And Prosper \V/"

[Bill Graham]

timewarp2008 wrote:
> On Jan 4, 8:11 pm, "Bill Graham" > wrote:
>> Jack Jarmush wrote:
>>> Hi,
>>> I fried a Behringer preamp pedal (PB100) by using the wrong polarity
>>> from a 12v battery. The preamp pedal accepts negative polarity but
>>> my battery plug is positive .. D'oh!
>>> Do you think it's fixable ?
>>> -JJ
>>
>> Yes. But when you do, put in a full wave bridge (4 diodes) so that
>> it can never happen again.
>
> Billy, can you tell the difference between a stock PB100 and a PB100
> with a full-wave bridge, in a double-blind listening test? Then why do
> you think it's worth the extra time and money? Hmmmmmm?

Because you can supply all your toys with an AC transformer, and it won't
matter a damn which polarity you feed them with if they all have full wave
bridges in them. I have a few items that are configured like that, and I
love em. I go out of my way to find them, and will always buy them all else
being equal.

[Bill Graham]

Doug McDonald wrote:
> On 1/5/2011 9:35 AM, Scott Dorsey wrote:
>> > wrote:
>>> On Jan 4, 8:11=A0pm, "Bill > wrote:
>>>> Jack Jarmush wrote:
>>>>> Hi,
>>>>> I fried a Behringer preamp pedal (PB100) by using the wrong
>>>>> polarity from a 12v battery. The preamp pedal accepts negative
>>>>> polarity but my battery plug is positive .. D'oh!
>>>>> Do you think it's fixable ?
>>>>> -JJ
>>>>
>>>> Yes. But when you do, put in a full wave bridge (4 diodes) so that
>>>> it can never happen again.
>
> Why a bridge? Why not just one diode? If you connect the wrong
> polarity, it just won't work, and you lose only one diode drop.
>
> Doug McDonald

Because with a bridge, you can connect it to a wall wart with the wrong
polarity, and it WILL work! But, the poster who pointed out that there will
be a volt+ drop across the diodes was on the money. You will have that.

[Bill Graham]

Kevin Aylward wrote:
> "Scott Dorsey" wrote in message ...
>
> timewarp2008 >> wrote:
>>> On Jan 4, 8:11=A0pm, "Bill Graham" >> wrote:
>>>>> Jack Jarmush wrote:
>>>>>>> Hi,
>>>>>>> I fried a Behringer preamp pedal (PB100) by using the wrong
>>>>>>> polarity from a 12v battery. The preamp pedal accepts negative
>>>>>>> polarity but my
>>>>>>> battery plug is positive .. D'oh!
>>>>>>> Do you think it's fixable ?
>>>>>>> -JJ
>>>>>
>>>>> Yes. But when you do, put in a full wave bridge (4 diodes) so
>>>>> that it can
>>>>> never happen again.
>>>
>>> Billy, can you tell the difference between a stock PB100 and a PB100
>>> with a full-wave bridge, in a double-blind listening test?
>> Then why do
>>> you think it's worth the extra time and money? Hmmmmmm?
>
>> Sadly, you probably CAN tell the difference,
>
> Depends what you mean. You will lose headroom, so things might clip
> earlier, but other than sort of thing there should be no audible
> difference at all if it been designed competently. Some battery
> pedals will have an internal regulator, if not, the design would be
> relying on the typical 80db-110db L.F. power supply rejection of the
> op-amps, and some RC filtering for HF.
Actually, this is the kind of thing I have done with relatively cheap, non
pro quality equipment. I have a lot of wall wart driven junk around my shop,
and getting the correct polarity is a PIA. I do like it when the
manufacturer puts the rectifiers in his equipment, and supplies you with an
AC transformer, however.....Works for me.

[timewarp2008]

On Jan 7, 3:26*am, "Bill Graham" > wrote:
> timewarp2008 wrote:
> > On Jan 4, 8:11 pm, "Bill Graham" > wrote:
> >> Jack Jarmush wrote:
> >>> Hi,
> >>> I fried a Behringer preamp pedal (PB100) by using the wrong polarity
> >>> from a 12v battery. The preamp pedal accepts negative polarity but
> >>> my battery plug is positive .. D'oh!
> >>> Do you think it's fixable ?
> >>> -JJ
>
> >> Yes. But when you do, put in a full wave bridge (4 diodes) so that
> >> it can never happen again.
>
> > Billy, can you tell the difference between a stock PB100 and a PB100
> > with a full-wave bridge, in a double-blind listening test? Then why do
> > you think it's worth the extra time and money? Hmmmmmm?
>
> Because you can supply all your toys with an AC transformer, and it won't
> matter a damn which polarity you feed them with if they all have full wave
> bridges in them. I have a few items that are configured like that, and I
> love em. I go out of my way to find them, and will always buy them all else
> being equal

So you advocate investing time and effort to modify a piece of audio
gear, without any double-blind evidence that you will be able to hear
a difference. Your reason is clearly included in the broad swath of
reasons that you sweepingly dismissed as "BS" on another thread,
insulting everyone disagreed with you. (Then, for comic effect I
guess, you combined a denial of your own insults with childish whining
that others had insulted you. It got a few laughs, so I guess the
comic effect was successful.)

But your slip is showing. That's a risk you take when you try to cover
a calf-length foundation made of lacy material (i.e. decorative, made
of thin threads, and full of holes) with a mere miniskirt of
understanding. When the slip gets too long, it can trip you up,
leaving you in the emperor's new clothes, and that exposes both the
seat of your intelligence and the ******** of your beliefs.

Now go and get two identical PB100's, replace the diode in one with
your recommended full-wave bridge, and listen to them both with
identical signals at levels which exercise the limits of perfomance at
the supply rails. Otherwise, you've just confirmed that you lost the
microphone argument, and that you yourself don't even believe in your
double-blind mumbo jumbo.

[Kevin Aylward[_4_]]

"timewarp2008" wrote in message
...

>
>> > Billy, can you tell the difference between a stock PB100 and a PB100
>> > with a full-wave bridge, in a double-blind listening test? Then why do
>> > you think it's worth the extra time and money? Hmmmmmm?
>
>> Because you can supply all your toys with an AC transformer, and it won't
>> matter a damn which polarity you feed them with if they all have full
>> wave
>> bridges in them. I have a few items that are configured like that, and I
>> love em. I go out of my way to find them, and will always buy them all
>> else
>> being equal


>Now go and get two identical PB100's, replace the diode in one with
>your recommended full-wave bridge, and listen to them both with
>identical signals at levels which exercise the limits of perfomance at
>the supply rails. Otherwise, you've just confirmed that you lost the
>microphone argument, and that you yourself don't even believe in your
>double-blind mumbo jumbo.

As I already explained, other than clipping level, units like this would
have to be very badly designed for there to be any difference in the sound.
Generally, they use op-amps with good psr, low distortion etc, such that
their gains are quite independent of supply voltage. Obviously, the version
with the diode will clip earlier, but I don't see a reason why anyone would
want to do that with this particular unit. Its just a Bass/Treble eq control
and level booster, designed to simply amplifier and shape the tone. Its not
designed as a distortion unit, and considering it must be capable of putting
out a couple of volts even with a couple of diode drops, there is no need
for the unit to hit its supply rail. Any guitar amp will be sensitive enough
to not require volts of input signal.

One does not need to do double blind tests on these type of units as,
assuming they are using half decent op amps, those sort of tests have
already been done many, many times, clearly showing that people can't tell
the difference between half decent op amps. Conceivably, if it were your
741, operating at closed loop gains of say > 100, some golden ears might
notice.

The story is not quite the same for vacuum tube rectifiers in tube/valve
amps, say being replaced by silicon diodes. Conceivably, someone might
notice a non clipping difference in that the psr for tube amps isn't usually
that great, and signal load resisters are returned to that supply.

Kevin Aylward B.Sc.

www.kevinaylward.co.uk
"Live Long And Prosper \V/"

[Trevor]

"Scott Dorsey" > wrote in message
...
> Jack Jarmush > wrote:
>>Hi,
>>I fried a Behringer preamp pedal (PB100) by using the wrong polarity
>>from a 12v battery. The preamp pedal accepts negative polarity but my
>>battery plug is positive .. D'oh!
>>Do you think it's fixable ?
>>-JJ
>
> Maybe. The problems start, though, with getting a schematic from
> Behringer and tracing through it and seeing what the possible failures
> are.

A proper tech could fix such a simple item without a schematic, although it
usually makes things a lot easier. Good luck getting one out of Behringer
though!

>If there's a protection diode, it's gone,

Literally, since IF there was a protection diode, the device would still be
fine! Sometimes manufacturers use a parallel diode to blow a fuse, rather
than a series diode however, when the voltage drop is considered critical.
In that case it should simply be a matter of replacing the fuse.


>and if there isn't
> whatever electrolytics are on the incoming line are gone. Trace
> downstream
> from there. It might not be that big a deal.
> This stuff is very cheaply made and it's intended to be disposable, which
> can be a problem.

Right, the cost of repair can often be more than a new device.

> But don't give up.

Not without taking a look inside anyway.

Trevor.

[Trevor]

"Gareth Magennis" > wrote in message
...
> Yes. I don't know this particular pedal, but many such devices use a
> single diode wired in reverse for polarity protection. If you use the
> wrong polarity power supply, this diode shorts out the incoming voltage,
> and burns to a short circuit, thus protecting the pedal, but sometimes
> breaking the power supply instead.

Rubbish! A diode is usually simply placed in series, and is reverse biased
with NO damage for wrong polarity. IF the voltage drop is critical a
parallel diode AND series fuse MAY be used. The Diode will NOT "burn to a
short circuit". Certainly not before the rest of the box was fried anyway!


> In many cases you can simply replace this diode and the pedal will work
> again.
> Find someone who can identify and replace a shorted diode without damaging
> the circuit board. A plumber, drummer, or motor mechanic are probably
> best avoided.

And people who can't tell a diode from a fuse.

Trevor.

[Trevor]

"Bill Graham" > wrote in message
...
> Jack Jarmush wrote:
>> Hi,
>> I fried a Behringer preamp pedal (PB100) by using the wrong polarity
>> from a 12v battery. The preamp pedal accepts negative polarity but my
>> battery plug is positive .. D'oh!
>> Do you think it's fixable ?
>> -JJ
>
> Yes. But when you do, put in a full wave bridge (4 diodes) so that it can
> never happen again.

What will four diodes do in this case that one wont, other than allowing it
working without changing polarity? The box could NOT be fried if it had ONE
series diode for protection.

Trevor.

[Gareth Magennis]

"Trevor" > wrote in message
...
>
> "Gareth Magennis" > wrote in message
> ...
>> Yes. I don't know this particular pedal, but many such devices use a
>> single diode wired in reverse for polarity protection. If you use the
>> wrong polarity power supply, this diode shorts out the incoming voltage,
>> and burns to a short circuit, thus protecting the pedal, but sometimes
>> breaking the power supply instead.
>


> Rubbish! A diode is usually simply placed in series, and is reverse biased
> with NO damage for wrong polarity. IF the voltage drop is critical a
> parallel diode AND series fuse MAY be used. The Diode will NOT "burn to a
> short circuit". Certainly not before the rest of the box was fried anyway!
>


Trevor, you clearly haven't the first clue what you are talking about, yet
profess to know everything.


My observations are based upon years of fixing broken equipment where the
owner has used the wrong polarity supply. This happens a lot.
Many devices DO use a simple reversed diode as protection. These diodes DO
burn to a short circuit, which is precisely why manufacturers DO use them
for just such a purpose.

I have replaced many of these shorted diodes and brought the unit back to
fully working condition, the 5 penny diode having done its job admirably,
just as the designer intended.


Gareth.

[Trevor]

"Gareth Magennis" > wrote in message
...
>>> Yes. I don't know this particular pedal, but many such devices use a
>>> single diode wired in reverse for polarity protection. If you use the
>>> wrong polarity power supply, this diode shorts out the incoming voltage,
>>> and burns to a short circuit, thus protecting the pedal, but sometimes
>>> breaking the power supply instead.
>>
>
>
>> Rubbish! A diode is usually simply placed in series, and is reverse
>> biased with NO damage for wrong polarity. IF the voltage drop is critical
>> a parallel diode AND series fuse MAY be used. The Diode will NOT "burn to
>> a short circuit". Certainly not before the rest of the box was fried
>> anyway!
>>
>
>
> Trevor, you clearly haven't the first clue what you are talking about, yet
> profess to know everything.
>

And you don't eh? :-)


> My observations are based upon years of fixing broken equipment where the
> owner has used the wrong polarity supply. This happens a lot.

Never said otherwise. Simply because often no polarity protection is
provided.


> Many devices DO use a simple reversed diode as protection. These diodes
> DO burn to a short circuit, which is precisely why manufacturers DO use
> them for just such a purpose.
> I have replaced many of these shorted diodes and brought the unit back to
> fully working condition, the 5 penny diode having done its job admirably,
> just as the designer intended.


A reversed diode will provide little protection for most devices since every
other electronic components will blow in about the same time.
I'm not saying SOME companies would NEVER do it, I'm simply saying it's
pretty pointless in general and is not common IME. The device would have to
be built to withstand the time in which it took the diode to blow, which
would be quick when conected to a car battery for instance, but not when
connected to a small wall-wart. Then you have to consider how the wall wart
will respond to having a short circuit placed on it, and whether blowing it
up is better than the device you are trying to save, and even whether there
is a chance of starting a fire!

All I can say is you must work at the really BAD end of town if you have so
much experience with such crappy designs. Thankfully I don't!
Is the only reason they dont use a simple series shottky diode instead the
extra cent or two involved?

Trevor.

[Gareth Magennis]

> A reversed diode will provide little protection for most devices since
> every other electronic components will blow in about the same time.



Not really.
A reversed diode clamps the voltage supplied to the equipment to around 0.6v
or so of the wrong polarity, until the diode burns to a short, at which time
the far more important equipment is subjected to no volts at all and the
power supply either blows a fuse or bites the dust.

[Scott Dorsey]

Trevor > wrote:
>"Gareth Magennis" > wrote in message
...
>> Yes. I don't know this particular pedal, but many such devices use a
>> single diode wired in reverse for polarity protection. If you use the
>> wrong polarity power supply, this diode shorts out the incoming voltage,
>> and burns to a short circuit, thus protecting the pedal, but sometimes
>> breaking the power supply instead.
>
>Rubbish! A diode is usually simply placed in series, and is reverse biased
>with NO damage for wrong polarity. IF the voltage drop is critical a
>parallel diode AND series fuse MAY be used. The Diode will NOT "burn to a
>short circuit". Certainly not before the rest of the box was fried anyway!

No. To avoid the diode drop, which is a big deal at these voltages, the
protection diode is normally in parallel with the load. Hopefully it
blows a fuse and everything is fine. Sometimes it blows the diode and
the diode surface gets wiped turning the diode into a short in both
directions.

This is also remarkably common in automobile applications where the diode
also helps protect against inductive kickback from the starter.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Bill Graham]

timewarp2008 wrote:
> On Jan 7, 3:26 am, "Bill Graham" > wrote:
>> timewarp2008 wrote:
>>> On Jan 4, 8:11 pm, "Bill Graham" > wrote:
>>>> Jack Jarmush wrote:
>>>>> Hi,
>>>>> I fried a Behringer preamp pedal (PB100) by using the wrong
>>>>> polarity from a 12v battery. The preamp pedal accepts negative
>>>>> polarity but my battery plug is positive .. D'oh!
>>>>> Do you think it's fixable ?
>>>>> -JJ
>>
>>>> Yes. But when you do, put in a full wave bridge (4 diodes) so that
>>>> it can never happen again.
>>
>>> Billy, can you tell the difference between a stock PB100 and a PB100
>>> with a full-wave bridge, in a double-blind listening test? Then why
>>> do you think it's worth the extra time and money? Hmmmmmm?
>>
>> Because you can supply all your toys with an AC transformer, and it
>> won't matter a damn which polarity you feed them with if they all
>> have full wave bridges in them. I have a few items that are
>> configured like that, and I love em. I go out of my way to find
>> them, and will always buy them all else being equal
>
> So you advocate investing time and effort to modify a piece of audio
> gear, without any double-blind evidence that you will be able to hear
> a difference. Your reason is clearly included in the broad swath of
> reasons that you sweepingly dismissed as "BS" on another thread,
> insulting everyone disagreed with you. (Then, for comic effect I
> guess, you combined a denial of your own insults with childish whining
> that others had insulted you. It got a few laughs, so I guess the
> comic effect was successful.)
>
> But your slip is showing. That's a risk you take when you try to cover
> a calf-length foundation made of lacy material (i.e. decorative, made
> of thin threads, and full of holes) with a mere miniskirt of
> understanding. When the slip gets too long, it can trip you up,
> leaving you in the emperor's new clothes, and that exposes both the
> seat of your intelligence and the ******** of your beliefs.
>
> Now go and get two identical PB100's, replace the diode in one with
> your recommended full-wave bridge, and listen to them both with
> identical signals at levels which exercise the limits of perfomance at
> the supply rails. Otherwise, you've just confirmed that you lost the
> microphone argument, and that you yourself don't even believe in your
> double-blind mumbo jumbo.

Hey. I am an electronics technician. I spent a large portion of my life
repairing these chassis, and for the most part, they were, "professional"
pieces of equipment. So, now you want me to put up with design flaws and
send the stuff off to someone else to repair it for me? Give me a break! I
will do what I want with my own stuff, and advise others to do the same.
This has nothint whatsoever to do with spending $9000 for a microphone. It
has to do with the convenience of getting one wall wart to work with several
different pieces of gear, and that's all it has to do with. If you don't
want to take my suggestions then don't. But be careful which wall wart you
use for your gear.....My secondary advice is to lable everything really
well, and get yourself a multimeter, while you're at it.....

[Bill Graham]

Kevin Aylward wrote:
> "timewarp2008" wrote in message
> ...
>
>>
>>>> Billy, can you tell the difference between a stock PB100 and a
>>>> PB100 with a full-wave bridge, in a double-blind listening test?
>>>> Then why do you think it's worth the extra time and money? Hmmmmmm?
>>
>>> Because you can supply all your toys with an AC transformer, and it
>>> won't matter a damn which polarity you feed them with if they all
>>> have full wave
>>> bridges in them. I have a few items that are configured like that,
>>> and I love em. I go out of my way to find them, and will always buy
>>> them all else
>>> being equal
>
>
>> Now go and get two identical PB100's, replace the diode in one with
>> your recommended full-wave bridge, and listen to them both with
>> identical signals at levels which exercise the limits of perfomance
>> at the supply rails. Otherwise, you've just confirmed that you lost
>> the microphone argument, and that you yourself don't even believe in
>> your double-blind mumbo jumbo.
>
> As I already explained, other than clipping level, units like this
> would have to be very badly designed for there to be any difference
> in the sound. Generally, they use op-amps with good psr, low
> distortion etc, such that their gains are quite independent of supply
> voltage. Obviously, the version with the diode will clip earlier, but
> I don't see a reason why anyone would want to do that with this
> particular unit. Its just a Bass/Treble eq control and level booster,
> designed to simply amplifier and shape the tone. Its not designed as
> a distortion unit, and considering it must be capable of putting out
> a couple of volts even with a couple of diode drops, there is no need
> for the unit to hit its supply rail. Any guitar amp will be sensitive
> enough to not require volts of input signal.
> One does not need to do double blind tests on these type of units as,
> assuming they are using half decent op amps, those sort of tests have
> already been done many, many times, clearly showing that people can't
> tell the difference between half decent op amps. Conceivably, if it
> were your 741, operating at closed loop gains of say > 100, some
> golden ears might notice.
>
> The story is not quite the same for vacuum tube rectifiers in
> tube/valve amps, say being replaced by silicon diodes. Conceivably,
> someone might notice a non clipping difference in that the psr for
> tube amps isn't usually that great, and signal load resisters are
> returned to that supply.
> Kevin Aylward B.Sc.
>
> www.kevinaylward.co.uk
> "Live Long And Prosper \V/"

I do have a couple of units that I replaced the standard wall warts with
regulated 18 VDC supplies. These things used two 9 volt batteries and I
noticed a difference in the sound when I used the unregulated wall warts the
manufacturer supplied me with. I bought the regulated, "switching supplies"
from another, independent power supply manufacturer. Of course, they were
the wrong polarity too....A lot of equipment made foreign uses center
negative supplies, and here in the US, we like center positive stuff.....It
can be annoying. I did find and bought a dozen little do dads that have a
2.5 mm plug on one side, and two connectors on the other, so I can use them
as polarity switches for wall warts.....I haven't tried them out yet, but
they look pretty good....

[Bill Graham]

Trevor wrote:
> "Bill Graham" > wrote in message
> ...
>> Jack Jarmush wrote:
>>> Hi,
>>> I fried a Behringer preamp pedal (PB100) by using the wrong polarity
>>> from a 12v battery. The preamp pedal accepts negative polarity but
>>> my battery plug is positive .. D'oh!
>>> Do you think it's fixable ?
>>> -JJ
>>
>> Yes. But when you do, put in a full wave bridge (4 diodes) so that
>> it can never happen again.
>
> What will four diodes do in this case that one wont, other than
> allowing it working without changing polarity? The box could NOT be
> fried if it had ONE series diode for protection.
>
> Trevor.

The full wave bridge does more than protect. It will allow you to use a wall
wart of either polarity, which in some applications is a real convenience. I
have a dozen or so chassis that use wall warts in either polarity, and I
have converted some of them to take AC transformers, or DC supplies....It
doesn't matter. This is very convenient, if you are as disorganized as I
(apparently) am.

[timewarp2008]

On Jan 7, 9:32*pm, "Bill Graham" > wrote:
> timewarp2008 wrote:
> > On Jan 7, 3:26 am, "Bill Graham" > wrote:
> >> timewarp2008 wrote:
> >>> On Jan 4, 8:11 pm, "Bill Graham" > wrote:
> >>>> Jack Jarmush wrote:
> >>>>> Hi,
> >>>>> I fried a Behringer preamp pedal (PB100) by using the wrong
> >>>>> polarity from a 12v battery. The preamp pedal accepts negative
> >>>>> polarity but my battery plug is positive .. D'oh!
> >>>>> Do you think it's fixable ?
> >>>>> -JJ
>
> >>>> Yes. But when you do, put in a full wave bridge (4 diodes) so that
> >>>> it can never happen again.
>
> >>> Billy, can you tell the difference between a stock PB100 and a PB100
> >>> with a full-wave bridge, in a double-blind listening test? Then why
> >>> do you think it's worth the extra time and money? Hmmmmmm?
>
> >> Because you can supply all your toys with an AC transformer, and it
> >> won't matter a damn which polarity you feed them with if they all
> >> have full wave bridges in them. I have a few items that are
> >> configured like that, and I love em. I go out of my way to find
> >> them, and will always buy them all else being equal
>
> > So you advocate investing time and effort to modify a piece of audio
> > gear, without any double-blind evidence that you will be able to hear
> > a difference. Your reason is clearly included in the broad swath of
> > reasons that you sweepingly dismissed as "BS" on another thread,
> > insulting everyone disagreed with you. (Then, for comic effect I
> > guess, you combined a denial of your own insults with childish whining
> > that others had insulted you. It got a few laughs, so I guess the
> > comic effect was successful.)
>
> > But your slip is showing. That's a risk you take when you try to cover
> > a calf-length foundation made of lacy material (i.e. decorative, made
> > of thin threads, and full of holes) with a mere miniskirt of
> > understanding. When the slip gets too long, it can trip you up,
> > leaving you in the emperor's new clothes, and that exposes both the
> > seat of your intelligence and the ******** of your beliefs.
>
> > Now go and get two identical PB100's, replace the diode in one with
> > your recommended full-wave bridge, and listen to them both with
> > identical signals at levels which exercise the limits of perfomance at
> > the supply rails. Otherwise, you've just confirmed that you lost the
> > microphone argument, and that you yourself don't even believe in your
> > double-blind mumbo jumbo.
>
> Hey. I am an electronics technician. I spent a large portion of my life
> repairing these chassis, and for the most part, they were, "professional"
> pieces of equipment. So, now you want me to put up with design flaws and
> send the stuff off to someone else to repair it for me? *Give me a break! I

Nope. I said nothing of the sort. You just made that up; a strawman
that you created out of nothingness. I noted that you advised someone
else to invest time and effort in modifying a piece of his sound
equipment, not yours, with absolutely no evidence that you or anyone
else would detect an improvement in a double-blind test. This, despite
that you previously used the term "BS" to describe all reasons for
valuing a piece of equipment that couldn't be demonstrated in a double
blind test. I never said anything about you sending anything off to
anyone to repair if for me. That's purely your invention, so go argue
with yourself about it. I'll bet you can't even win an argument with
yourself.

> I will do what I want with my own stuff, and advise others to do the same..

Go ahead and do what you want with your own stuff. Who else would give
a flying **** what you do with your own crappy equipment? I didn't say
anything about what you should do with your own stuff. You were
recommending that SOMEONE ELSE modify his stuff, and for reasons that
you previously called "BS". I know that you have trouble following a
thread, but at least try to keep up with what you just quoted and
replied to. If you just want to invent stuff, and then yell at it to
get off your lawn, you don't need Usenet. You can rant at yourself,
and any flock of pigeons that comes by, right from the street in front
of your house.

> This has nothint whatsoever to do with spending $9000 for a microphone. It
> has to do with the convenience of getting one wall wart to work with several
> different pieces of gear, and that's all it has to do with.

No, it has to do with something that you value in a piece of sound
equipment, that you can't validate with a double-blind test. You can
try to dance around that simple fact, and the disconnect between that
simple fact and your previous many dozens of ranting tirades on
another thread. But the contrast is striking. You insisted, loudly and
incessantly, that only a double-blind test could be used to evaluate
sound equipment. Now you're implicitly admitting that it's simply not
true, but you won't explicitly own up to it, because you're too busy
rescuing yourself from the attack of the strawmen that you just
created.

> If you don't want to take my suggestions then don't.

Of course. I won't. I don't need your permission to ignore your
advice. I won't be tearing anything open and adding extra diodes so I
can have lower voltages on the supply rails, just so I'll be able to
plug power supplies in backwards.

> But be careful which wall wart you use for your gear.....

And don't plug your dick into a light bulb socket. Is it "blatantly
obvious night" tonight? Don't plug things together wrong? Duh!
Elementary. But can you prove it with a double-blind test? Of course
not!

> My secondary advice is to lable everything really well,
> and get yourself a multimeter, while you're at it.....

Yup, I guess it IS blatantly obvious night. And it's blatantly obvious
that you think audio equipment can be evaluated for characteristics
that can not be judged by a double-blind test, despite your lenghty
tantrums to the contrary. You advised someone to degrade the usable
dynamic range of his equipment so he could connect it carelessly like
a deaf old geezer with his head so far up his ass that it's amazing he
can still fit his foot in his mouth. If you spent all those many years
as a technician, you should at least be able to plug something in
without blowing it up. But I guess you have to make everything in your
life idiot-proof so it will be safe in your own presence.

My secondary advice is to get yourself a protective helmet, while
you're at it. In case you accidentally drop an anvil on your head in
the bathtub.

[PStamler]

Bill Graham wrote:

>Hey. I am an electronics technician. I spent a large portion of my life
>repairing these chassis, and for the most part, they were, "professional"
>pieces of equipment.

You're an electronics technician and you spent a lot of your life
fixing broken effects pedals? Funny, I thought you said you worked on
particle accelerators.

Peace,
Paul

[Bill Graham]

timewarp2008 wrote:
> On Jan 7, 9:32 pm, "Bill Graham" > wrote:
>> timewarp2008 wrote:
>>> On Jan 7, 3:26 am, "Bill Graham" > wrote:
>>>> timewarp2008 wrote:
>>>>> On Jan 4, 8:11 pm, "Bill Graham" > wrote:
>>>>>> Jack Jarmush wrote:
>>>>>>> Hi,
>>>>>>> I fried a Behringer preamp pedal (PB100) by using the wrong
>>>>>>> polarity from a 12v battery. The preamp pedal accepts negative
>>>>>>> polarity but my battery plug is positive .. D'oh!
>>>>>>> Do you think it's fixable ?
>>>>>>> -JJ
>>
>>>>>> Yes. But when you do, put in a full wave bridge (4 diodes) so
>>>>>> that it can never happen again.
>>
>>>>> Billy, can you tell the difference between a stock PB100 and a
>>>>> PB100 with a full-wave bridge, in a double-blind listening test?
>>>>> Then why do you think it's worth the extra time and money?
>>>>> Hmmmmmm?
>>
>>>> Because you can supply all your toys with an AC transformer, and it
>>>> won't matter a damn which polarity you feed them with if they all
>>>> have full wave bridges in them. I have a few items that are
>>>> configured like that, and I love em. I go out of my way to find
>>>> them, and will always buy them all else being equal
>>
>>> So you advocate investing time and effort to modify a piece of audio
>>> gear, without any double-blind evidence that you will be able to
>>> hear a difference. Your reason is clearly included in the broad
>>> swath of reasons that you sweepingly dismissed as "BS" on another
>>> thread, insulting everyone disagreed with you. (Then, for comic
>>> effect I guess, you combined a denial of your own insults with
>>> childish whining that others had insulted you. It got a few laughs,
>>> so I guess the comic effect was successful.)
>>
>>> But your slip is showing. That's a risk you take when you try to
>>> cover a calf-length foundation made of lacy material (i.e.
>>> decorative, made of thin threads, and full of holes) with a mere
>>> miniskirt of understanding. When the slip gets too long, it can
>>> trip you up, leaving you in the emperor's new clothes, and that
>>> exposes both the seat of your intelligence and the ******** of your
>>> beliefs.
>>
>>> Now go and get two identical PB100's, replace the diode in one with
>>> your recommended full-wave bridge, and listen to them both with
>>> identical signals at levels which exercise the limits of perfomance
>>> at the supply rails. Otherwise, you've just confirmed that you lost
>>> the microphone argument, and that you yourself don't even believe
>>> in your double-blind mumbo jumbo.
>>
>> Hey. I am an electronics technician. I spent a large portion of my
>> life repairing these chassis, and for the most part, they were,
>> "professional" pieces of equipment. So, now you want me to put up
>> with design flaws and send the stuff off to someone else to repair
>> it for me? Give me a break! I
>
> Nope. I said nothing of the sort. You just made that up; a strawman
> that you created out of nothingness. I noted that you advised someone
> else to invest time and effort in modifying a piece of his sound
> equipment, not yours, with absolutely no evidence that you or anyone
> else would detect an improvement in a double-blind test. This, despite
> that you previously used the term "BS" to describe all reasons for
> valuing a piece of equipment that couldn't be demonstrated in a double
> blind test. I never said anything about you sending anything off to
> anyone to repair if for me. That's purely your invention, so go argue
> with yourself about it. I'll bet you can't even win an argument with
> yourself.
>
>> I will do what I want with my own stuff, and advise others to do the
>> same.
>
> Go ahead and do what you want with your own stuff. Who else would give
> a flying **** what you do with your own crappy equipment? I didn't say
> anything about what you should do with your own stuff. You were
> recommending that SOMEONE ELSE modify his stuff, and for reasons that
> you previously called "BS". I know that you have trouble following a
> thread, but at least try to keep up with what you just quoted and
> replied to. If you just want to invent stuff, and then yell at it to
> get off your lawn, you don't need Usenet. You can rant at yourself,
> and any flock of pigeons that comes by, right from the street in front
> of your house.
>
>> This has nothint whatsoever to do with spending $9000 for a
>> microphone. It has to do with the convenience of getting one wall
>> wart to work with several different pieces of gear, and that's all
>> it has to do with.
>
> No, it has to do with something that you value in a piece of sound
> equipment, that you can't validate with a double-blind test. You can
> try to dance around that simple fact, and the disconnect between that
> simple fact and your previous many dozens of ranting tirades on
> another thread. But the contrast is striking. You insisted, loudly and
> incessantly, that only a double-blind test could be used to evaluate
> sound equipment. Now you're implicitly admitting that it's simply not
> true, but you won't explicitly own up to it, because you're too busy
> rescuing yourself from the attack of the strawmen that you just
> created.
>
>> If you don't want to take my suggestions then don't.
>
> Of course. I won't. I don't need your permission to ignore your
> advice. I won't be tearing anything open and adding extra diodes so I
> can have lower voltages on the supply rails, just so I'll be able to
> plug power supplies in backwards.
>
>> But be careful which wall wart you use for your gear.....
>
> And don't plug your dick into a light bulb socket. Is it "blatantly
> obvious night" tonight? Don't plug things together wrong? Duh!
> Elementary. But can you prove it with a double-blind test? Of course
> not!
>
>> My secondary advice is to lable everything really well,
>> and get yourself a multimeter, while you're at it.....
>
> Yup, I guess it IS blatantly obvious night. And it's blatantly obvious
> that you think audio equipment can be evaluated for characteristics
> that can not be judged by a double-blind test, despite your lenghty
> tantrums to the contrary. You advised someone to degrade the usable
> dynamic range of his equipment so he could connect it carelessly like
> a deaf old geezer with his head so far up his ass that it's amazing he
> can still fit his foot in his mouth. If you spent all those many years
> as a technician, you should at least be able to plug something in
> without blowing it up. But I guess you have to make everything in your
> life idiot-proof so it will be safe in your own presence.
>
> My secondary advice is to get yourself a protective helmet, while
> you're at it. In case you accidentally drop an anvil on your head in
> the bathtub.

Reguardless of your stupid blather, I recommend that anyone who uses
equipment powered by wall warts, install full wave bridges in it to
eliminate the necessity of matching the wall wart polarity to the equipment.
It makes life a lot easier. Especially if you have to break into the
equipment for repair anyway. Take the advice of an old ET, over an irate
idiot.

[Bill Graham]

PStamler wrote:
> Bill Graham wrote:
>
>> Hey. I am an electronics technician. I spent a large portion of my
>> life repairing these chassis, and for the most part, they were,
>> "professional" pieces of equipment.
>
> You're an electronics technician and you spent a lot of your life
> fixing broken effects pedals? Funny, I thought you said you worked on
> particle accelerators.
>
> Peace,
> Paul

Yeah, that too. I have had a long and varied life, sonny. One of these days,
after your ear wetness drys out a bit, you may be able to say the same
thing. Of course, since you are unable to learn from my mistakes, you will
have to make your own.

[Kevin Aylward[_4_]]

"Trevor" wrote in message
...


"Gareth Magennis" >> wrote in message
...
>>>>>> Yes. I don't know this particular pedal, but many such devices use a
>>>>>> single diode wired in reverse for polarity protection. If you use
>>>>>> the wrong polarity power supply, this diode shorts out the incoming
>>>>>> voltage, and burns to a short circuit, thus protecting the pedal, but
>>>>>> sometimes breaking the power supply instead.
>>>>
>>
>>
>>>> Rubbish! A diode is usually simply placed in series, and is reverse
>>>> biased with NO damage for wrong polarity. IF the voltage drop is
>>>> critical a parallel diode AND series fuse MAY be used. The Diode will
>>>> NOT "burn to a short circuit". Certainly not before the rest of the box
>>>> was fried anyway!
>>>>
>>
>> Many devices DO use a simple reversed diode as protection. These diodes
>> DO burn to a short circuit, which is precisely why manufacturers DO use
>> them for just such a purpose.
>> I have replaced many of these shorted diodes and brought the unit back to
>> fully working condition, the 5 penny diode having done its job admirably,
>> just as the designer intended.

>A reversed diode will provide little protection for most devices since
>every other electronic components will blow in about the same time.

Depends on how limited the supply current is. For most devices, with the
most common supplies, the principle actually works. The diodes need to be
relatively high current ones though.

>I'm not saying SOME companies would NEVER do it, I'm simply saying it's
>pretty pointless in general and is not common IME.

I disagree that "in general" its pointless. For a significant number of
applications the reverse diode will work quite well. I don't have the
statistics on how often its done. It is done, but there are other ways to do
it.

>The device would have to be built to withstand the time in which it took
>the diode to blow, which

Sure.

>would be quick when connected to a car battery for instance, but not when
>connected to a small wall-wart.

I would say that it would be relatively rare that guitar pedals are
connected to car batteries. The assumption would generally be that they are
connected to a wall wart PS.

> Then you have to consider how the wall wart will respond to having a short
> circuit placed on it, and whether blowing it up

Typically, wall warts have a fair amount of series resistance. Short time
shorts on them, in my experience, don't usually bother them much.

>is better than the device you are trying to save, and even whether there is
>a chance of starting a fire!

The idea is that one plugs/switches on the wall wart and notes immediately
whether or not the pedal has powered up. If not, one disconnects it.

Its not a perfect way to protect something, but it is done, and in most
cases, is probably ok, despite it being something like fingernails down a
school blackboard to us analogue design engineers.


Kevin Aylward B.Sc.
www.kevinaylward.co.uk
"Live Long And Prosper \V/"

[Trevor]

"Gareth Magennis" > wrote in message
...
> Not really.
> A reversed diode clamps the voltage supplied to the equipment to around
> 0.6v or so of the wrong polarity, until the diode burns to a short, at
> which time the far more important equipment is subjected to no volts at
> all and the power supply either blows a fuse or bites the dust.

This sounds like a very specialised "diode" to me, one that burns to a short
rather than goes open circuit as most do, and one that handles FAR less
current than a typical plug pack can put out. Since most can you'd just blow
the plug pack and any consequences that arise from that.

Obviously NOT a regular diode at all, and still NOT the best way to handle a
reverse polarity IMO.

Trevor.

[Scott Dorsey]

Trevor > wrote:
>"Gareth Magennis" > wrote in message
...
>> Not really.
>> A reversed diode clamps the voltage supplied to the equipment to around
>> 0.6v or so of the wrong polarity, until the diode burns to a short, at
>> which time the far more important equipment is subjected to no volts at
>> all and the power supply either blows a fuse or bites the dust.
>
>This sounds like a very specialised "diode" to me, one that burns to a short
>rather than goes open circuit as most do, and one that handles FAR less
>current than a typical plug pack can put out. Since most can you'd just blow
>the plug pack and any consequences that arise from that.

Actually, that's how most 1N4000-series diodes fail under overcurrent.
The junction overheats and melts and when the thing congeals you just have
a solid slab of conductive silicon inside instead of a semiconductor.

Technicians call this "wiping" because of the analogy to similar transistor
failures where molten silicon is wiped all over the surface of the mesa.

>Obviously NOT a regular diode at all, and still NOT the best way to handle a
>reverse polarity IMO.

You'll have to speak to the manufacturers about that, because it's the
design that you see in most auto electronics and a lot of designs using
wall warts also. It's a good idea to have a fuse upstream at the very
least, though.

Honestly, this is the most common failure mode for consumer products
receiving the wrong polarity, with exploded electrolytics the second.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Trevor]

"Scott Dorsey" > wrote in message
...
> No. To avoid the diode drop, which is a big deal at these voltages,

How so? IF you are using a plug pack (as was the case we are discussing)
then simply specify a higher voltage one.

Now IF you also provide reverse polarity protection on the batteries, I
would agree, and any power wastage there is critical, not just the voltage
drop, but will one extra diode to the external power socket really kill
their profit margins?


> protection diode is normally in parallel with the load. Hopefully it
> blows a fuse and everything is fine.

Exactly as I stated in the first place! The parallel diode should always use
a fuse as well, and you want the fuse to blow, not the diode to go short
circuit as was claimed. It still seems to me that any manufacturer who does
otherwise is incompetent .


>Sometimes it blows the diode and
> the diode surface gets wiped turning the diode into a short in both
> directions.

Obviously a very specialised diode, but still no idea what makes it better
than using a fuse as well?

> This is also remarkably common in automobile applications where the diode
> also helps protect against inductive kickback from the starter.

Yes, I pointed out that for car use there might be some point, but since I
never work on car stuff I'd forgotten, and since we were talking about a
guitar pedal and plug pack, I did not think it relevant originally.

Trevor.

[John Williamson]

Trevor wrote:
> "Gareth Magennis" > wrote in message
> ...
>> Not really.
>> A reversed diode clamps the voltage supplied to the equipment to around
>> 0.6v or so of the wrong polarity, until the diode burns to a short, at
>> which time the far more important equipment is subjected to no volts at
>> all and the power supply either blows a fuse or bites the dust.
>
> This sounds like a very specialised "diode" to me, one that burns to a short
> rather than goes open circuit as most do, and one that handles FAR less
> current than a typical plug pack can put out. Since most can you'd just blow
> the plug pack and any consequences that arise from that.
>
> Obviously NOT a regular diode at all, and still NOT the best way to handle a
> reverse polarity IMO.
>
Not the best or most elegant way, but definitely the cheapest to install
at the factory. The diode only has to last long enough to blow the fuse
or trip the overload circuitry in the supply. A diode rated at 5A will
protect equipment drawing up to a couple of amps, given normal fusing
arrangements. If the fuse is PCB mounted, then a competent engineer will
replace the fuse and the diode. Most wallwarts will fail in a safe
manner, if they fail due to overloading.

It also means that a cheaper power supply can be used, as you don't need
to allow for the voltage drop across a bridge. Pennies count, when
you're building thousands.

--
Tciao for Now!

John.

[Trevor]

"Bill Graham" > wrote in message
...
>> What will four diodes do in this case that one wont, other than
>> allowing it working without changing polarity? The box could NOT be
>> fried if it had ONE series diode for protection.
>>
>
> The full wave bridge does more than protect. It will allow you to use a
> wall wart of either polarity, which in some applications is a real
> convenience.

Yep I just said that, at the expense of cost, and two diode drops as others
have said.


>I have a dozen or so chassis that use wall warts in either polarity, and I
>have converted some of them to take AC transformers, or DC supplies....It
>doesn't matter. This is very convenient, if you are as disorganized as I
>(apparently) am.

I agree that having them all run off an external AC input is far easier, but
many manufacturers don't include a full wave rectifier and voltage regulator
in equipment that is primarily designed to run off batteries, for the
obvious reason of saving money. Unlike you, most people are not willing to
make the necessary modifications to all their equipment.

But if it works for you, go for it!

Trevor.

[Trevor]

"Kevin Aylward" > wrote in message
...
> Depends on how limited the supply current is. For most devices, with the
> most common supplies, the principle actually works. The diodes need to be
> relatively high current ones though.

OK, now I'm confused, how does a high current diode go "short circuit" when
placed across a low power plug pack, as the poster I originally responded to
claimed?

Sure it will probably blow the plug pack, but is that really the best you
can do when simply adding a fuse might allow everything to survive?

>>I'm not saying SOME companies would NEVER do it, I'm simply saying it's
>>pretty pointless in general and is not common IME.
>
> I disagree that "in general" its pointless. For a significant number of
> applications the reverse diode will work quite well. I don't have the
> statistics on how often its done. It is done, but there are other ways to
> do it.

Let's get this straight, I said in my very first post that it IS done, and
there is a good reason, what I said is that a parallel diode SHOULD also
have a fuse, and that a normal diode will probably go open circuit rather
than short circit anyway.


> I would say that it would be relatively rare that guitar pedals are
> connected to car batteries. The assumption would generally be that they
> are connected to a wall wart PS.

Right, which is why I did not consider methodes used for car equipment
relevant.


> Typically, wall warts have a fair amount of series resistance. Short time
> shorts on them, in my experience, don't usually bother them much.

Or blow normal diodes, so I guess these are rather specialised ones we are
talking about that also go short circuit when passing a pretty low current.


> The idea is that one plugs/switches on the wall wart and notes immediately
> whether or not the pedal has powered up. If not, one disconnects it.

People who connect it wrong in the first place cannot be relied upon to
notice it not powering up immediately.


> Its not a perfect way to protect something,

Or even a very good one.

>but it is done, and in most cases, is probably ok, despite it being
>something like fingernails down a school blackboard to us analogue design
>engineers.

And for the last time, WHY not add a series fuse so the parallel diode has
something to blow other than the plug pack???

Trevor.

[hank alrich]

PStamler > wrote:

> Bill Graham wrote:
>
> >Hey. I am an electronics technician. I spent a large portion of my life
> >repairing these chassis, and for the most part, they were, "professional"
> >pieces of equipment.
>
> You're an electronics technician and you spent a lot of your life
> fixing broken effects pedals? Funny, I thought you said you worked on
> particle accelerators.
>
> Peace,
> Paul

If you're good at it a par tickle will accelerate her. If you're not
good at it you'll get slapped.

--
shut up and play your guitar * http://hankalrich.com/
http://armadillomusicproductions.com/who'slistening.html
http://www.sonicbids.com/HankandShaidriAlrichwithDougHarman

[Trevor]

"Scott Dorsey" > wrote in message
...
> Trevor > wrote:
>>This sounds like a very specialised "diode" to me, one that burns to a
>>short
>>rather than goes open circuit as most do, and one that handles FAR less
>>current than a typical plug pack can put out. Since most can you'd just
>>blow
>>the plug pack and any consequences that arise from that.
>
> Actually, that's how most 1N4000-series diodes fail under overcurrent.

Maybe, but no guarantees. So if it goes O/C then NO protection at all.
Adding that fuse is looking better and better!


>>Obviously NOT a regular diode at all, and still NOT the best way to handle
>>a
>>reverse polarity IMO.
>
> You'll have to speak to the manufacturers about that, because it's the
> design that you see in most auto electronics and a lot of designs using
> wall warts also. It's a good idea to have a fuse upstream at the very
> least, though.

Which is what I said in the very beginning, and got jumped on.


> Honestly, this is the most common failure mode for consumer products
> receiving the wrong polarity, .

Yep, and I still think that's simply because manufactuers are happy for you
to blow up their equipment, if they can claim user error and charge you to
fix it, or sell you a new one. IF they were made to fix it free because of
their lousy design it would be a different matter!


>with exploded electrolytics the second

That's because of some VERY poor Chineses electro's having been made for
many years.

Trevor.

[Trevor]

"John Williamson" > wrote in message
...
>> Obviously NOT a regular diode at all, and still NOT the best way to
>> handle a reverse polarity IMO.
>>
> Not the best or most elegant way, but definitely the cheapest to install
> at the factory. The diode only has to last long enough to blow the fuse

Better check my original post, that's what I said already. IF there is a
fuse, why would you need the diode to go short circuit as claimed?


> or trip the overload circuitry in the supply.

Yeh right! Cheap plug packs with overload circuitry, but more expensive
equipment without even a fuse :-)


>A diode rated at 5A will protect equipment drawing up to a couple of amps,
>given normal fusing arrangements.

And HOW does a 5A diode go "short circuit" as originally claimed, when
connected to a plug pack?


>If the fuse is PCB mounted, then a competent engineer will replace the fuse
>and the diode.

If there is a fuse then my claim was right all along and the person I
responed to was incorrect in claiming the protection is from the diode going
S/C surely?


>Most wallwarts will fail in a safe manner, if they fail due to overloading.

What a world, cheap plug packs are expected to be far better designed than
the more expensive equipment connected to them!
(Not saying you are wong of course.)


> It also means that a cheaper power supply can be used, as you don't need
> to allow for the voltage drop across a bridge. Pennies count, when you're
> building thousands.

Sure, and for plug packs too, which is why I wouldn't rely on them to be
better designed than the equipment connected to them.

Trevor.

[RD Jones]

On Jan 8, 3:31*pm, "Trevor" > wrote:

> Let's get this straight, I said in my very first post that it IS done, and
> there is a good reason, what I said is that a parallel diode SHOULD also
> have a fuse, and that a normal diode will probably go open circuit rather
> than short circit anyway.

It's been my experienced that the dominant failure mode is going
short,
both for typical low voltage 12-15V stuff and high voltage tube plate
supplies.
I have seen open diodes, YMMV.

> Right, which is why I did not consider methodes used for car equipment
> relevant.

anode, cathode, diode, methode ;->

> > Typically, wall warts have a fair amount of series resistance. Short time
> > shorts on them, in my experience, don't usually bother them much.

They rarely have much if any regulation. The voltage actually supplied
will
be well in excess of that needed to overcome the drop of a bridge.

rd

[William Sommerwerck]

> I said in my very first post that it IS done, and there
> is a good reason, what I said is that a parallel diode
> SHOULD also have a fuse...

Just to clarify a point... The fuse for the parallel diode should be in
series with the power supply, "ahead of" the diode. If it were in series
with the diode, there would be no reverse-polarity protection.

[John Williamson]

Trevor wrote:
> "John Williamson" > wrote in message
> ...
>>> Obviously NOT a regular diode at all, and still NOT the best way to
>>> handle a reverse polarity IMO.
>>>
>> Not the best or most elegant way, but definitely the cheapest to install
>> at the factory. The diode only has to last long enough to blow the fuse
>
> Better check my original post, that's what I said already. IF there is a
> fuse, why would you need the diode to go short circuit as claimed?
>
The "fuse" may not be a seperate element, but a design feature of the
PCB. I've seen at least one consumer item where the onboard rechargeable
battery is protected from reverse polarity by a surface mounted fuse and
a diode. It worked too.... Unfortunately, the fuse wasn't available as a
part from the makers, and there was no current rating shown, so the item
was beyond economic repair, as it would have needed a new PCB, which was
available at just a bit more than the cost of a replacement unit.
>
>> or trip the overload circuitry in the supply.
>
> Yeh right! Cheap plug packs with overload circuitry, but more expensive
> equipment without even a fuse :-)
>
Regulated ones are quite common, and all the ones I've used have
overload protection. It's even standard (Thermal and overcurrent ) in
the three terminal voltage regulator ICs I can buy retail for a few
pence. Modern wallwarts tend to be SMPS types anyway, protection's
designed in to the ICs used, and most makers just use the chip makers'
reference circuit.
>
>> A diode rated at 5A will protect equipment drawing up to a couple of amps,
>> given normal fusing arrangements.
>
> And HOW does a 5A diode go "short circuit" as originally claimed, when
> connected to a plug pack?
>
Under reverse polarity conditions, it *is* near enough to a short cicuit
even before failure. Under normal conditions, it's open circuit. As has
been said elsewhere, the reverse voltage will not rise above about 0.6
volts. As has also been said, some diodes have a common behaviour when
mistreated of going short circuit, with embarassing results in, say, a
bridge rectifier.
>
>> If the fuse is PCB mounted, then a competent engineer will replace the fuse
>> and the diode.
>
> If there is a fuse then my claim was right all along and the person I
> responed to was incorrect in claiming the protection is from the diode going
> S/C surely?
>
The "fuse" is sometimes a marginally rated track on the PCB. I've even
made the odd one off design more tamper proof by making a link wire out
of fuse wire. *I* knew about it, but the end user didn't, though it was
documented in the service manual. That saved a couple of problems from
someone replacing a repeatedly blowing fuse with a larger one...
>
>> Most wallwarts will fail in a safe manner, if they fail due to overloading.
>
> What a world, cheap plug packs are expected to be far better designed than
> the more expensive equipment connected to them!
> (Not saying you are wong of course.)
>
Wallwarts sold here *have* to comply with EC standards which specify
safe acceptance of overload conditions. A lot of the wallwarts I use are
sold for use worldwide, with a snap on adaptor to connect to the local
sockets and capable of accepting any mains input voltage from 90 - 270
volts RMS.

The equipment connected to them has no such requirement, especially if
it's designed to be battery powered, as the battery design will
generally limit fault currents to safe levels.
>
>> It also means that a cheaper power supply can be used, as you don't need
>> to allow for the voltage drop across a bridge. Pennies count, when you're
>> building thousands.
>
> Sure, and for plug packs too, which is why I wouldn't rely on them to be
> better designed than the equipment connected to them.
>
Wallwart makers use standard, off the shelf ICs, the ICs are designed
failsafe, and are cheaper than a special without protection unless your
numbers are truly huge. In fact, unless you are making huge numbers of
wallwarts, it's cheaper to buy in your already type approved items from
a specialist maker, who make the same design for dozens of equipment
suppliers, and just change the label, or, in some cases, the external
casing.

If these aren't good enough due to poor noise figures or some other
reason, then your equipment will be expensive enough to justify a
properly designed power supply, and the cost will reflect that.

--
Tciao for Now!

John.

[Gareth Magennis]

"William Sommerwerck" > wrote in message
...
>> I said in my very first post that it IS done, and there
>> is a good reason, what I said is that a parallel diode
>> SHOULD also have a fuse...
>
> Just to clarify a point... The fuse for the parallel diode should be in
> series with the power supply, "ahead of" the diode. If it were in series
> with the diode, there would be no reverse-polarity protection.
>
>


Just to further clarify, the diode IS the fuse.
If a Numpty connects the wrong PSU you are still going to have to open the
unit to change the fuse. A fuse in a fuseholder is going to take lots of
space and a human being to fit it, thus incurring significant extra
manufacturing expense. Changing a soldered in PCB fuse is the same as
changing a diode.
Also, fuses often go just because they are tired of the incessant inrush
currents, not because of any fault, and the fuse holders can also suffer
from dirt and dry joints and metal fatigue,, so fitting one not only incurs
more exspense, it actually makes the unit significantly less reliable.


Wall warts do not have internal fuses. Very few exceptions indeed.




Gareth.

[Scott Dorsey]

Gareth Magennis > wrote:
>
>Just to further clarify, the diode IS the fuse.

No, that would be a series diode, not a parallel diode. Which is a thing
you will see sometimes, but not as often.

This thread is just getting really silly.

>Wall warts do not have internal fuses. Very few exceptions indeed.

No, but they often have transformers that are designed to fail safely,
since so many do. Of course, they also skimp on primary windings so
sometimes they fail in really bad ways too.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Fred[_13_]]

Trevor wrote:
> "Scott Dorsey" > wrote in message
> ...
>> No. To avoid the diode drop, which is a big deal at these voltages,
>
> How so? IF you are using a plug pack (as was the case we are
> discussing) then simply specify a higher voltage one.
>
> Now IF you also provide reverse polarity protection on the batteries,
> I would agree, and any power wastage there is critical, not just the
> voltage drop, but will one extra diode to the external power socket
> really kill their profit margins?
>
>
>> protection diode is normally in parallel with the load. Hopefully it
>> blows a fuse and everything is fine.
>
> Exactly as I stated in the first place! The parallel diode should
> always use a fuse as well, and you want the fuse to blow, not the
> diode to go short circuit as was claimed. It still seems to me that
> any manufacturer who does otherwise is incompetent .
>
>
>> Sometimes it blows the diode and
>> the diode surface gets wiped turning the diode into a short in both
>> directions.
>
> Obviously a very specialised diode, but still no idea what makes it
> better than using a fuse as well?

Nothing specialized at all, Trevor. The dominant failure mode for all
silicon diodes, including zeners, is to short out. An open silicon diode
that hasn't suffered mechanical abuse is a rare thing indeed.

Fred


>> This is also remarkably common in automobile applications where the
>> diode also helps protect against inductive kickback from the starter.
>
> Yes, I pointed out that for car use there might be some point, but
> since I never work on car stuff I'd forgotten, and since we were
> talking about a guitar pedal and plug pack, I did not think it
> relevant originally.
> Trevor.

[William Sommerwerck]

> Just to further clarify, the diode IS the fuse.

Not if it's in parallel, which is what we were talking about.

Now, if it's /guaranteed/ that the diode will short out (rather than
opening), and you don't mind shorting the power source, it will work.

[Fred[_13_]]

William Sommerwerck wrote:
>> Just to further clarify, the diode IS the fuse.
>
> Not if it's in parallel, which is what we were talking about.
>
> Now, if it's /guaranteed/ that the diode will short out (rather than
> opening), and you don't mind shorting the power source, it will work.

Moog used to protect its Polymoog (several hundred analog ICs that
could be destroyed by a power supply failure) with 16V 5W zeners on
the outputs of the +/- 15V supplies. The zener invariably failed shorted
if its associated supply tried to go high, blowing the fuse instead of a
fistfull of ICs.

Short circuit *IS* the failure mode of silicon diodes. The semiconductor
melts into a (non-semi) conductor. Even a 1N4148 signal diode, rated
at 200mA, will pass several amps after failing before exploding to an
open circuit. After failing its resistance is very close to zero, so it takes
a lot of current to generate enough heat to destroy it.

Fred

[Bill Graham]

Trevor wrote:
> "Bill Graham" > wrote in message
> ...
>>> What will four diodes do in this case that one wont, other than
>>> allowing it working without changing polarity? The box could NOT be
>>> fried if it had ONE series diode for protection.
>>>
>>
>> The full wave bridge does more than protect. It will allow you to
>> use a wall wart of either polarity, which in some applications is a
>> real convenience.
>
> Yep I just said that, at the expense of cost, and two diode drops as
> others have said.
>
>
>> I have a dozen or so chassis that use wall warts in either polarity,
>> and I have converted some of them to take AC transformers, or DC
>> supplies....It doesn't matter. This is very convenient, if you are
>> as disorganized as I (apparently) am.
>
> I agree that having them all run off an external AC input is far
> easier, but many manufacturers don't include a full wave rectifier
> and voltage regulator in equipment that is primarily designed to run
> off batteries, for the obvious reason of saving money. Unlike you,
> most people are not willing to make the necessary modifications to
> all their equipment.
> But if it works for you, go for it!
>
> Trevor.

Yes. I have a couple of "Rolls" pre amps that use twin 9 volt batteries, and
I wanted to run them off of wall warts. I ended up buying $30 switching wall
warts that were regulated for them, because the standard unregulated
supplies introduced too much humm. Not all equipment is suitable for
unregulated wall warts. Especially equipment designed to run off of
batteries.

[Arny Krueger]

"Trevor" > wrote in message
u
> "Scott Dorsey" > wrote in message
> ...
>> Trevor > wrote:

>>> This sounds like a very specialised "diode" to me, one
>>> that burns to a short

Nothing specialized at all. IME, this is how 4000-series rectifiers fry.

>>> rather than goes open circuit as most do, and one that
>>> handles FAR less current than a typical plug pack can
>>> put out. Since most can you'd just blow
>>> the plug pack and any consequences that arise from that.

>> Actually, that's how most 1N4000-series diodes fail
>> under overcurrent.

Agreed.

> Maybe, but no guarantees. So if it goes O/C then NO
> protection at all. Adding that fuse is looking better and
> better!

There's usually something, whether an actual fuse or a low value resistor,
that functions like a fuse.

In modern times, the wall-wart is a regulated, short-circuit-protected
switchmode power supply. I see little else on new equipment sold in the US.

Transformer-based wall warts are rapidly becoming a thing of the past. The
small size and weight of the little switchmode plugs makes them the
preferred solution.

[Arny Krueger]

"John Williamson" > wrote in
message

> Regulated ones are quite common, and all the ones I've
> used have overload protection.

Exactly.

> It's even standard
> (Thermal and overcurrent ) in the three terminal voltage
> regulator ICs I can buy retail for a few pence.

And, its been that way for decades.

> Modern wallwarts tend to be SMPS types anyway,

A key point. I've found nothing but SMPS external power supplies in the box
with the small electronics I've bought lately.

> protection's designed in to the ICs used, and most makers just use the
> chip makers' reference circuit.

It has obviously become less costly to build a SMPS than the old
transformer-based dealies. I've paid less than $2 each delivered for ca. 5
watt plug-mounted SMPS in small quantities.

>>> A diode rated at 5A will protect equipment drawing up
>>> to a couple of amps, given normal fusing arrangements.
>>
>> And HOW does a 5A diode go "short circuit" as originally
>> claimed, when connected to a plug pack?

Scott described how this happens, with his usual exactness and attention to
detail.

> Under reverse polarity conditions, it *is* near enough to
> a short cicuit even before failure. Under normal
> conditions, it's open circuit. As has been said
> elsewhere, the reverse voltage will not rise above about
> 0.6 volts. As has also been said, some diodes have a
> common behaviour when mistreated of going short circuit,
> with embarassing results in, say, a bridge rectifier.

I find far more shorted diodes in fried power supplies than any other
failure mode.

>>> If the fuse is PCB mounted, then a competent engineer
>>> will replace the fuse and the diode.

>> If there is a fuse then my claim was right all along and
>> the person I responed to was incorrect in claiming the
>> protection is from the diode going S/C surely?

> The "fuse" is sometimes a marginally rated track on the
> PCB. I've even made the odd one off design more tamper
> proof by making a link wire out of fuse wire. *I* knew
> about it, but the end user didn't, though it was
> documented in the service manual. That saved a couple of
> problems from someone replacing a repeatedly blowing fuse
> with a larger one...

Or, a very small value resistor.

>>> Most wallwarts will fail in a safe manner, if they fail
>>> due to overloading.

>> What a world, cheap plug packs are expected to be far
>> better designed than the more expensive equipment
>> connected to them! (Not saying you are wong of course.)

> Wallwarts sold here *have* to comply with EC standards
> which specify safe acceptance of overload conditions. A
> lot of the wallwarts I use are sold for use worldwide,
> with a snap on adaptor to connect to the local sockets
> and capable of accepting any mains input voltage from 90
> - 270 volts RMS.

As Scott and others have said, the wall wart market has gone SMPS.

> The equipment connected to them has no such requirement,
> especially if it's designed to be battery powered, as the
> battery design will generally limit fault currents to
> safe levels.

SMPS simply stop putting out current if they go into overcurrent limiting.

>>> It also means that a cheaper power supply can be used,
>>> as you don't need to allow for the voltage drop across
>>> a bridge. Pennies count, when you're building thousands.

>> Sure, and for plug packs too, which is why I wouldn't
>> rely on them to be better designed than the equipment
>> connected to them.

> Wallwart makers use standard, off the shelf ICs, the ICs
> are designed failsafe, and are cheaper than a special
> without protection unless your numbers are truly huge. In
> fact, unless you are making huge numbers of wallwarts,
> it's cheaper to buy in your already type approved items
> from a specialist maker, who make the same design for
> dozens of equipment suppliers, and just change the label,
> or, in some cases, the external casing.

This seems to be accepted practice.

> If these aren't good enough due to poor noise figures or
> some other reason, then your equipment will be expensive
> enough to justify a properly designed power supply, and
> the cost will reflect that.

The SMPS wall warts have to pass FCC Part 15, so they can't be all that
dirty.

[Kevin Aylward[_4_]]

"Trevor" wrote in message
u...

"Kevin Aylward" >> wrote in message
...
>> Depends on how limited the supply current is. For most devices, with the
>> most common supplies, the principle actually works. The diodes need to be
>> relatively high current ones though.

>OK, now I'm confused, how does a high current diode go "short circuit" when
>placed across a low power plug pack, as the poster I originally responded
>to claimed?
>Sure it will probably blow the plug pack, but is that really the best you
>can do when simply adding a fuse might allow everything to survive?

I am not claiming that the designers/manufactures of the pedals are
specifically relying on the diode going s/c, as some others are. It may
happen as a secondary consideration though. Its difficult to say what's the
motivation of all the manufactures are. Its debatable how many actually know
they they are doing. It surprisingly difficult to find competent analogue
designers nowadays.

Its quite conceivable that they are relying on the inherent current limited
supply of a wall wart such that the pedal will still work fine after being
reconnected the correct way. Its a probability thing. The pedal manufacture
probably don't care that the wall wart may fail, because its not "their"
problem if one does not operate the unit as directed in the instruction
manual. However, they would rather that the pedal still works when powered
up again correctly. This won't happen if the diode circuit is designed to
fail.


>>>>I'm not saying SOME companies would NEVER do it, I'm simply saying it's
>>>>pretty pointless in general and is not common IME.
>>
>> I disagree that "in general" its pointless. For a significant number of
>> applications the reverse diode will work quite well. I don't have the
>> statistics on how often its done. It is done, but there are other ways to
>> do it.

>> The idea is that one plugs/switches on the wall wart and notes
>> immediately whether or not the pedal has powered up. If not, one
>> disconnects it.

>People who connect it wrong in the first place cannot be relied upon to
>notice it not powering up immediately.

Its a probability thing. I think it is reasonable to expect that a fair
number of people will pay a bit of attention when connecting up a power
supply for the *first* time.

The manufacture is not going to design for all worse case *misuse*
conditions. Its usually too expensive to do this. They just accept that some
units are going to fail/blow up other bits of kit if operated incorrectly.
Of course, a competent designer/manufacture should design the internal
circuit for worst case component variations for all normal use. i.e. the
unit should function correctly whatever op-amp, transistor, resistor is used
of the specified type. e.f. 10k +/-5%,

>> Its not a perfect way to protect something,

>Or even a very good one.

Its often better than nothing.

>>but it is done, and in most cases, is probably ok, despite it being
>>something like fingernails down a school blackboard to us analogue design
>>engineers.

>And for the last time, WHY not add a series fuse so the parallel diode has
>something to blow other than the plug pack???

Because there is a fair probability that a short term reverse polarity may
not make anything fail, such that simply reconnecting up the correct way
will make things all dandy again. A fuse on the circuit board will cost
money and board space, and also guaranteed to stop the unit working, even
when powered up correctly afterwards. I can't stress enough how much
manufactures work to save every cent in manufacturing costs.

Kevin Aylward B.Sc.
www.kevinaylward.co.uk
"Live Long And Prosper \V/"

[Kevin Aylward[_4_]]

"Trevor" wrote in message
u...


"Scott Dorsey" >> wrote in message

>>with exploded electrolytics the second

>That's because of some VERY poor Chineses electro's having been made for
>many years.

It is not really a quality issue. Pretty much any electrolytic will explode
if subjected to reverse polarity for long enough. Some of us used to do this
deliberately when they were a lot younger.


Kevin Aylward B.Sc.
www.kevinaylward.co.uk
"Live Long And Prosper \V/"

[RD Jones]

On Jan 9, 10:14*am, "Kevin Aylward" >
wrote:
> >> Depends on how limited the supply current is. For most devices, with the
> >> most common supplies, the principle actually works. The diodes need to be
> >> relatively high current ones though.
> >OK, now I'm confused, how does a high current diode go "short circuit" when
> >placed across a low power plug pack, as the poster I originally responded
> >to claimed?
> >Sure it will probably blow the plug pack, but is that really the best you
> >can do when simply adding a fuse might allow everything to survive?
>
> I am not claiming that the designers/manufactures of the pedals are
> specifically relying on the diode going s/c, as some others are. It may
> happen as a secondary consideration though. Its difficult to say what's the
> motivation of all the manufactures are. Its debatable how many actually know
> they they are doing. It surprisingly difficult to find competent analogue
> designers nowadays.

The diode doesn't need to short to protect, it just needs to conduct
(or block as the case may be).
Reverse polarity of only 6 or 7 tenths of a volt would have a much
lower chance
of causing damage wouldn't it ?

rd

[Kevin Aylward[_4_]]

"RD Jones" wrote in message
...

On Jan 9, 10:14 am, "Kevin Aylward" >>
wrote:
>> >>>> Depends on how limited the supply current is. For most devices, with
>> >>>> the
>> >>>> most common supplies, the principle actually works. The diodes need
>> >>>> to be
>> >>>> relatively high current ones though.
>> >>OK, now I'm confused, how does a high current diode go "short circuit"
>> >>when
>> >>placed across a low power plug pack, as the poster I originally
>> >>responded
>> >>to claimed?
>> >>Sure it will probably blow the plug pack, but is that really the best
>> >>you
>> >>can do when simply adding a fuse might allow everything to survive?
>>
>> I am not claiming that the designers/manufactures of the pedals are
>> specifically relying on the diode going s/c, as some others are. It may
>> happen as a secondary consideration though. Its difficult to say what's
>> the
>> motivation of all the manufactures are. Its debatable how many actually
>> know
>> they they are doing. It surprisingly difficult to find competent analogue
>> designers nowadays.

>The diode doesn't need to short to protect, it just needs to conduct
>(or block as the case may be).
>Reverse polarity of only 6 or 7 tenths of a volt would have a much
>lower chance
>of causing damage wouldn't it ?

You've lost me there mate. I thought I was actually clear on explaining the
whole rational for that method of protection. I will need to do better.

Sure, that's the the whole point. You don't want to have the diode go s/c,
and sure, the diode on its own should protect the devices if its got a low
enough nominal Vbe. A Schottky would be better.


Kevin Aylward B.Sc.
www.kevinaylward.co.uk
"Live Long And Prosper \V/"

[Sam Trenholme]

In article >,
timewarp2008 > wrote:

>your double-blind mumbo jumbo.

With add due respect, I smell a troll. Or, more accurately, a crackpot.
To wit:

* This guy is using an anonymous account. Yeah, this is allowed in
Usenet, but is not common; most other posters here (including myself)
post with our real names.

* This guy is posting from Google groups. Yeah, good postings come from
there but all of the trolls who I have killfiled (actually,
blacklisted, since trn 3.6 has buggy killfile handling) are using
Google groups.

* This guy believes a crackpot theory: That double blind tests are not
scientifically valid.

* This guy is holding on to a resentment because of a flamewar he was
recently in.

I am considering blacklisting "timewarp" postings, but if any other
regulars can tell me of constructive postings this user has made, I am
less likely to do so.

Has this guy made any constructive postings? Or is his contributions to
r.a.p consist of flaming anyone to a crisp who tells him that "if you
can't hear the difference in a double blind test, then the difference
can't be heard".

- Sam

--
#Sam Trenholme http://samiam.org -- Usenet user since September 1993#
######## My email address is at http://samiam.org/mailme.php ########
# The following script works around an annoyance in the Nano Editor #
cat | awk '{a=a $0 "\n";if($0 ~ /[a-zA-Z0-9]/){printf("%s",a);a=""}}'

[Sam Trenholme]

>I noted that you advised someone else to invest time and effort in
>modifying a piece of his sound equipment, not yours, with absolutely no
>evidence that you or anyone else would detect an improvement in a
>double-blind test.

His suggestion is a modification to the power supply part of the
circuit. Not the audio part. His suggestion would make the device in
question more reliable; it's not to change its sound.

And, as I just posted, if you really believe that people can hear things
that they can't distinguish when given a double-blind test, you may be
finding yourself in my killfile. Yes, you have a right to believe that,
but my experience is that people who believe that tend to be
loud-mouthed, obnoxious, and do not make any positive contributions to
r.a.p. The fact that you aren't killfiled yet means you still have my
respect (outright trolls end up in my killfile faster than you can say
"adios").

- Sam

--
#Sam Trenholme http://samiam.org -- Usenet user since September 1993#
######## My email address is at http://samiam.org/mailme.php ########
# The following script works around an annoyance in the Nano Editor #
cat | awk '{a=a $0 "\n";if($0 ~ /[a-zA-Z0-9]/){printf("%s",a);a=""}}'

[Trevor]

"William Sommerwerck" > wrote in message
...
>> I said in my very first post that it IS done, and there
>> is a good reason, what I said is that a parallel diode
>> SHOULD also have a fuse...
>
> Just to clarify a point... The fuse for the parallel diode should be in
> series with the power supply, "ahead of" the diode. If it were in series
> with the diode, there would be no reverse-polarity protection.

Right, as I already said in my first reply. I don't feel the need to keep
repeating it all just because some people dídn't read it propely and keep
pretending I was wrong, and saying exactly the same thing I said in the
first place. What some others claimed is that no fuse is used, and they rely
on the diode to go S/C and protect the device, possibly by blowing up the
plug pack in the process. That is all I disagreed with. Sure it may be done
by some really bad companies, but fortunately it's not all that common IME.

Trevor.

[Trevor]

"Gareth Magennis" > wrote in message
...
>> Just to clarify a point... The fuse for the parallel diode should be in
>> series with the power supply, "ahead of" the diode. If it were in series
>> with the diode, there would be no reverse-polarity protection.
>>
>
> Just to further clarify, the diode IS the fuse.

A parallel diode cannot be a series fuse, and is a pretty poor alternative
IMO. Placing a continuous short on the power supply just to save a fuse is
not what I call good design!


> If a Numpty connects the wrong PSU you are still going to have to open the
> unit to change the fuse. A fuse in a fuseholder is going to take lots of
> space and a human being to fit it, thus incurring significant extra
> manufacturing expense. Changing a soldered in PCB fuse is the same as
> changing a diode.

Sure, but provides better protection without the risk of blowing up the plug
pack.


> Also, fuses often go just because they are tired of the incessant inrush
> currents, not because of any fault, and the fuse holders can also suffer
> from dirt and dry joints and metal fatigue,, so fitting one not only
> incurs more exspense, it actually makes the unit significantly less
> reliable.

Nope, as you said they rarely put in a fuse holder.

> Wall warts do not have internal fuses. Very few exceptions indeed.

Actually the transformers are usually required to be fused here to prevent a
fire. No idea about the USA requirements, and switch mode supplies.

Trevor.

[Trevor]

"William Sommerwerck" > wrote in message
...

> Now, if it's /guaranteed/ that the diode will short out (rather than
> opening), and you don't mind shorting the power source, it will work.

Right, and the reason you would *want* or *choose* to rely on that is?

Trevor.

[Trevor]

"John Williamson" > wrote in message
...
>> Cheap plug packs with overload circuitry, but more expensive equipment
>> without even a fuse :-)
>>
> Regulated ones are quite common,

As are unregulated ones. Far more common than regulated ones IME.


> and all the ones I've used have overload protection. It's even standard
> (Thermal and overcurrent ) in the three terminal voltage regulator ICs I
> can buy retail for a few pence. Modern wallwarts tend to be SMPS types
> anyway, protection's designed in to the ICs used, and most makers just use
> the chip makers' reference circuit.

No argument, my point is if a plug pack can be properly designed and
protected for a few dollars selling price, why is far more expensive
equipment poorly designed to save a cent or two?


>>> A diode rated at 5A will protect equipment drawing up to a couple of
>>> amps, given normal fusing arrangements.
>>
>> And HOW does a 5A diode go "short circuit" as originally claimed, when
>> connected to a plug pack?
>>
> Under reverse polarity conditions, it *is* near enough to a short cicuit
> even before failure.

Well yes of course, but that's not what was claimed. A few hundred mA plug
pack is supposed to melt the diode to a blob of S/C metal according to many.
But I bet nobody uses a 5A diode to save the cost of a fuse however.


>> If there is a fuse then my claim was right all along and the person I
>> responed to was incorrect in claiming the protection is from the diode
>> going S/C surely?
>>
> The "fuse" is sometimes a marginally rated track on the PCB.

Yep, but that still does not rely on the diode alone. And does remove the
S/C from the power supply.


>I've even made the odd one off design more tamper proof by making a link
>wire out of fuse wire. *I* knew about it, but the end user didn't, though
>it was documented in the service manual. That saved a couple of problems
>from someone replacing a repeatedly blowing fuse with a larger one...

Not so uncommon, and many do it just to save the cost of a glass fuse and/or
fuseholder. Still better than ONLY a parallel diode IMO.


>> What a world, cheap plug packs are expected to be far better designed
>> than the more expensive equipment connected to them!
>> (Not saying you are wong of course.)
>>
> Wallwarts sold here *have* to comply with EC standards which specify safe
> acceptance of overload conditions. A lot of the wallwarts I use are sold
> for use worldwide, with a snap on adaptor to connect to the local sockets
> and capable of accepting any mains input voltage from 90 - 270 volts RMS.

Yes they are required to here as well. My point is that IF a $5 plug pack
can be properly designed and protected, why cannot a more expensive piece of
equipment. Just plain stupidity and greed IMO.


> The equipment connected to them has no such requirement, especially if
> it's designed to be battery powered, as the battery design will generally
> limit fault currents to safe levels.

As I said already, ONE (extra) diode in series with the external power input
jack is all that's required.

Trevor.

[Trevor]

"Arny Krueger" > wrote in message
...
>>> And HOW does a 5A diode go "short circuit" as originally
>>> claimed, when connected to a plug pack?
>
> Scott described how this happens, with his usual exactness and attention
> to detail.

NO he didn't. Please detail how YOU *Think* a small plug pack can cause a 5A
diode to go S/C. Obviously the diode will still reduce the voltage to ~0.6V,
but a 5A diode will NOT melt into a S/C as described. It will simply provide
a near S/C on the power supply for as long as it's connected or the supply
blows up. All just to save the cost of an additional series fuse or series
diode. How sad. However considering the extra cost of 5A diodes, I bet they
are not too common in gutar pedals either!


> As Scott and others have said, the wall wart market has gone SMPS.

Sure, and I've seen plenty die when overloaded despite the idea that they
are fully protected. The regulations are simply to stop fires, not to
prevent the plug packs themselves blowing up.

> SMPS simply stop putting out current if they go into overcurrent limiting.

Right, if they survive. Many are just as poorly designed as the equipment we
are discussing however. Many are recalled here every year because they fail
to meet safety standards. Many of those recalls after they have been on the
market for some time.


Trevor.

[Trevor]

"Arny Krueger" > wrote in message
...
> Nothing specialized at all. IME, this is how 4000-series rectifiers fry.

Not when connected to a couple of hundred mA plug pack though :-)
And I'd still not guarantee my designs on it always doing that! Put a big
enough current through a diode and the lead wires melt, no longer a S/C is
it?


> There's usually something, whether an actual fuse or a low value resistor,
> that functions like a fuse.

Which is what I said all along, and the diode would NOT be required to
'melt" to a S/C as claimed then.


> In modern times, the wall-wart is a regulated, short-circuit-protected
> switchmode power supply. I see little else on new equipment sold in the
> US.
>
> Transformer-based wall warts are rapidly becoming a thing of the past.


No argument, but there are still *millions* in every day use however! One
simply should not design a piece of equipment poorly based on the idea that
the latest plug packs will save you a cent or two on the cost of a diode!

Trevor.

[Trevor]

"Kevin Aylward" > wrote in message
...
> I am not claiming that the designers/manufactures of the pedals are
> specifically relying on the diode going s/c, as some others are. It may
> happen as a secondary consideration though. Its difficult to say what's
> the motivation of all the manufactures are. Its debatable how many
> actually know they they are doing. It surprisingly difficult to find
> competent analogue designers nowadays.

So true.

> Its quite conceivable that they are relying on the inherent current
> limited supply of a wall wart such that the pedal will still work fine
> after being reconnected the correct way. Its a probability thing. The
> pedal manufacture probably don't care that the wall wart may fail, because
> its not "their" problem if one does not operate the unit as directed in
> the instruction manual. However, they would rather that the pedal still
> works when powered up again correctly. This won't happen if the diode
> circuit is designed to fail.

OK, that's the only reason anyone has given so far that makes any sense. I'd
still prefer to see a series diode on the external supply socket as well.
That pretty much guarantees no harm will come to anything.



>>People who connect it wrong in the first place cannot be relied upon to
>>notice it not powering up immediately.
>
> Its a probability thing. I think it is reasonable to expect that a fair
> number of people will pay a bit of attention when connecting up a power
> supply for the *first* time.

I usually check the supply polarity as well, but what OTHER people consider
"reasonable" is another matter :-)


> The manufacture is not going to design for all worse case *misuse*
> conditions. Its usually too expensive to do this.

One extra diode is hardly going to kill their profits.

>They just accept that some units are going to fail/blow up other bits of
>kit if operated incorrectly.

In fact some appear to design for it.

>>> Its not a perfect way to protect something,
>
>>Or even a very good one.
>
> Its often better than nothing.

Hardly a recommendation.


>>And for the last time, WHY not add a series fuse so the parallel diode has
>>something to blow other than the plug pack???
>
> Because there is a fair probability that a short term reverse polarity may
> not make anything fail, such that simply reconnecting up the correct way
> will make things all dandy again. A fuse on the circuit board will cost
> money and board space, and also guaranteed to stop the unit working, even
> when powered up correctly afterwards. I can't stress enough how much
> manufactures work to save every cent in manufacturing costs.

Unfortunately true, all this to save the cost of one additional series
diode, and a fuseable link on the PC board as a last resort.

Trevor.

[Trevor]

"Kevin Aylward" > wrote in message
...
>>That's because of some VERY poor Chineses electro's having been made for
>>many years.
>
> It is not really a quality issue. Pretty much any electrolytic will
> explode if subjected to reverse polarity for long enough.

Of course, the problem recently is that they "explode" when connected and
operating as designed, whereas many other electros are still operating daily
after 30 or 40 years.

Trevor.

[Bill Graham]

Sam Trenholme wrote:
>> I noted that you advised someone else to invest time and effort in
>> modifying a piece of his sound equipment, not yours, with absolutely
>> no evidence that you or anyone else would detect an improvement in a
>> double-blind test.
>
> His suggestion is a modification to the power supply part of the
> circuit. Not the audio part. His suggestion would make the device in
> question more reliable; it's not to change its sound.
>
> And, as I just posted, if you really believe that people can hear
> things that they can't distinguish when given a double-blind test,
> you may be finding yourself in my killfile. Yes, you have a right to
> believe that, but my experience is that people who believe that tend
> to be loud-mouthed, obnoxious, and do not make any positive
> contributions to r.a.p. The fact that you aren't killfiled yet means
> you still have my respect (outright trolls end up in my killfile
> faster than you can say "adios").
>
> - Sam

I was only advocating what I have done myself, successfully, on several
peices of my own equipment. It is a simple reversing switch that
automatically directs the current to the correct terminal. Its not rocket
science. I don't know why anyone would object to it. If used on equipment
that normally takes unregulated wall wart supplies, it will not introduce
excessive hum. If you have delicate equipment that can suffer from excessive
humm, I advise buying a regulated, switching supply type wall wart. These
exist, and they usually sell in the $30 to $40 range, which is well within
the budget of some people who are accustomed to purchasing $9000
microphones...:^)

[RD Jones]

On Jan 10, 3:17*am, "Bill Graham" > wrote:
> Sam Trenholme wrote:
> >> I noted that you advised someone else to invest time and effort in
> >> modifying a piece of his sound equipment, not yours, with absolutely
> >> no evidence that you or anyone else would detect an improvement in a
> >> double-blind test.
>
> > His suggestion is a modification to the power supply part of the
> > circuit. *Not the audio part. *His suggestion would make the device in
> > question more reliable; it's not to change its sound.
>
> > And, as I just posted, if you really believe that people can hear
> > things that they can't distinguish when given a double-blind test,
> > you may be finding yourself in my killfile. *Yes, you have a right to
> > believe that, but my experience is that people who believe that tend
> > to be loud-mouthed, obnoxious, and do not make any positive
> > contributions to r.a.p. The fact that you aren't killfiled yet means
> > you still have my respect (outright trolls end up in my killfile
> > faster than you can say "adios").
>
> > - Sam
>
> I was only advocating what I have done myself, successfully, on several
> peices of my own equipment. It is a simple reversing switch that
> automatically directs the current to the correct terminal. Its not rocket
> science. I don't know why anyone would object to it. If used on equipment
> that normally takes unregulated wall wart supplies, it will not introduce
> excessive hum. If you have delicate equipment that can suffer from excessive
> humm, I advise buying a regulated, switching supply type wall wart. These
> exist, and they usually sell in the $30 to $40 range, which is well within
> the budget of some people who are accustomed to purchasing $9000
> microphones...:^)

The horses are dead, they are starting to smell.
Please holster your whips.

[Arny Krueger]

"Trevor" > wrote in message
u

> "Arny Krueger" > wrote in message
> ...

>> Nothing specialized at all. IME, this is how 4000-series
>> rectifiers fry.

> Not when connected to a couple of hundred mA plug pack
> though :-)

I don't know why you'd say that. Remember that 4000-series diodes are rated
at a thousand mA. I've seen them run several times that for days. Peak
rating is 30,000 mA.

> And I'd still not guarantee my designs on it always doing
> that! Put a big enough current through a diode and the
> lead wires melt, no longer a S/C is it?

This is an absoultely rediculous comment.

>> There's usually something, whether an actual fuse or a
>> low value resistor, that functions like a fuse.

> Which is what I said all along, and the diode would NOT
> be required to 'melt" to a S/C as claimed then.

IME 1N4000 series protection diodes are usually not permanently damaged
when they protect the equipment.

>> In modern times, the wall-wart is a regulated,
>> short-circuit-protected switchmode power supply. I see
>> little else on new equipment sold in the US.
>>
>> Transformer-based wall warts are rapidly becoming a
>> thing of the past.

> No argument, but there are still *millions* in every day
> use however! One simply should not design a piece of
> equipment poorly based on the idea that the latest plug
> packs will save you a cent or two on the cost of a diode!

I suspect that the circuit board real estate to mount them is worth more in
most designs than the IN4001 diode that populates them.

[Arny Krueger]

"Kevin Aylward" > wrote in
message
> "Trevor" wrote in message
> u...
>
>
> "Scott Dorsey" >> wrote in message
>
>>> with exploded electrolytics the second
>
>> That's because of some VERY poor Chineses electro's
>> having been made for many years.
>
> It is not really a quality issue. Pretty much any
> electrolytic will explode if subjected to reverse
> polarity for long enough. Some of us used to do this
> deliberately when they were a lot younger.

You've obviously not seen any of the results of the recent Chinese
electrolytic capacitor debacle. Parts that are properly installed and
operated well within their ratings will bulge or explode within a year of
being placed into service, if not sooner.

[Arny Krueger]

"Trevor" > wrote in message
u
> "Arny Krueger" > wrote in message
> ...
>>>> And HOW does a 5A diode go "short circuit" as
>>>> originally claimed, when connected to a plug pack?
>>
>> Scott described how this happens, with his usual
>> exactness and attention to detail.
>
> NO he didn't. Please detail how YOU *Think* a small plug
> pack can cause a 5A diode to go S/C.

IME a wall wart that is rated at a few hunder mA won't damage a IN4001
series diode in full forward conduction.

[Scott Dorsey]

In article >,
Sam Trenholme > wrote:
>>I noted that you advised someone else to invest time and effort in
>>modifying a piece of his sound equipment, not yours, with absolutely no
>>evidence that you or anyone else would detect an improvement in a
>>double-blind test.
>
>His suggestion is a modification to the power supply part of the
>circuit. Not the audio part. His suggestion would make the device in
>question more reliable; it's not to change its sound.

In the case of a gain pedal where it may be one transistor, some resistors
and a coupling capacitor, it's hard to break apart the power supply part
and the audio part. Most of these things have no regulation, no constant
current sources, and some of them even rely on transistor leakage for bias
which is a no-no everywhere else in the world.

You could argue this is an incompetent design, but then again if people like
the way it sounds, who cares?
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Scott Dorsey]

In article >,
Arny Krueger > wrote:
>"Kevin Aylward" > wrote in
>message
>> "Trevor" wrote in message
>> u...
>>
>>
>> "Scott Dorsey" >> wrote in message
>>
>>>> with exploded electrolytics the second
>>
>>> That's because of some VERY poor Chineses electro's
>>> having been made for many years.
>>
>> It is not really a quality issue. Pretty much any
>> electrolytic will explode if subjected to reverse
>> polarity for long enough. Some of us used to do this
>> deliberately when they were a lot younger.
>
>You've obviously not seen any of the results of the recent Chinese
>electrolytic capacitor debacle. Parts that are properly installed and
>operated well within their ratings will bulge or explode within a year of
>being placed into service, if not sooner.

This is true, but irrelevant to the original subject which was reversed
polarity.

When people reverse polarity on DC inputs, they tend to blow protection
diodes and to blow up capacitors which weren't protected.

Crappy Chinese (and Taiwanese) electrolytics made badly will fail without
polarity reversal, but that's not the subject we were discussing.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[hank alrich]

Arny Krueger > wrote:

> "Kevin Aylward" > wrote in
> message
> > "Trevor" wrote in message
> > u...
> >
> >
> > "Scott Dorsey" >> wrote in message
> >
> >>> with exploded electrolytics the second
> >
> >> That's because of some VERY poor Chineses electro's
> >> having been made for many years.
> >
> > It is not really a quality issue. Pretty much any
> > electrolytic will explode if subjected to reverse
> > polarity for long enough. Some of us used to do this
> > deliberately when they were a lot younger.
>
> You've obviously not seen any of the results of the recent Chinese
> electrolytic capacitor debacle. Parts that are properly installed and
> operated well within their ratings will bulge or explode within a year of
> being placed into service, if not sooner.

Industrial espionage karma blowback. Made a mess of several things here.

--
shut up and play your guitar * http://hankalrich.com/
http://armadillomusicproductions.com/who'slistening.html
http://www.sonicbids.com/HankandShaidriAlrichwithDougHarman

[hank alrich]

RD Jones > wrote:

> On Jan 10, 3:17 am, "Bill Graham" > wrote:
> > Sam Trenholme wrote:
> > >> I noted that you advised someone else to invest time and effort in
> > >> modifying a piece of his sound equipment, not yours, with absolutely
> > >> no evidence that you or anyone else would detect an improvement in a
> > >> double-blind test.
> >
> > > His suggestion is a modification to the power supply part of the
> > > circuit. Not the audio part. His suggestion would make the device in
> > > question more reliable; it's not to change its sound.
> >
> > > And, as I just posted, if you really believe that people can hear
> > > things that they can't distinguish when given a double-blind test,
> > > you may be finding yourself in my killfile. Yes, you have a right to
> > > believe that, but my experience is that people who believe that tend
> > > to be loud-mouthed, obnoxious, and do not make any positive
> > > contributions to r.a.p. The fact that you aren't killfiled yet means
> > > you still have my respect (outright trolls end up in my killfile
> > > faster than you can say "adios").
> >
> > > - Sam
> >
> > I was only advocating what I have done myself, successfully, on several
> > peices of my own equipment. It is a simple reversing switch that
> > automatically directs the current to the correct terminal. Its not rocket
> > science. I don't know why anyone would object to it. If used on equipment
> > that normally takes unregulated wall wart supplies, it will not introduce
> > excessive hum. If you have delicate equipment that can suffer from excessive
> > humm, I advise buying a regulated, switching supply type wall wart. These
> > exist, and they usually sell in the $30 to $40 range, which is well within
> > the budget of some people who are accustomed to purchasing $9000
> > microphones...:^)
>
> The horses are dead, they are starting to smell.
> Please holster your whips.

He more likely gonna whip his holster.

--
shut up and play your guitar * http://hankalrich.com/
http://armadillomusicproductions.com/who'slistening.html
http://www.sonicbids.com/HankandShaidriAlrichwithDougHarman

[Trevor]

"Arny Krueger" > wrote in message
...
>> Not when connected to a couple of hundred mA plug pack
>> though :-)
>
> I don't know why you'd say that. Remember that 4000-series diodes are
> rated at a thousand mA. I've seen them run several times that for days.
> Peak rating is 30,000 mA.

Exactly, so how again does a small plug pack make one "melt to a S/C blob"
as suggested?
You obviously missed the fact that I never said they wouldn't conduct as
designed.


>> And I'd still not guarantee my designs on it always doing
>> that! Put a big enough current through a diode and the
>> lead wires melt, no longer a S/C is it?
>
> This is an absoultely rediculous comment.

How so? Any signal diode that WILL "melt" at a few hundred mA as suggested
by others, will have small lead wires that will fuse when placed on a car
battery, as was also suggested as one reason for doing it.


>> Which is what I said all along, and the diode would NOT
>> be required to 'melt" to a S/C as claimed then.
>
> IME 1N4000 series protection diodes are usually not permanently damaged
> when they protect the equipment.

Right, just as I said. No need to "melt" though.
You really should read what *I* wrote.


>>> Transformer-based wall warts are rapidly becoming a
>>> thing of the past.
>
>> No argument, but there are still *millions* in every day
>> use however! One simply should not design a piece of
>> equipment poorly based on the idea that the latest plug
>> packs will save you a cent or two on the cost of a diode!
>
> I suspect that the circuit board real estate to mount them is worth more
> in most designs than the IN4001 diode that populates them.

Now who is being rediculous? And no need to use a 4001 for an extra series
diode on a guitar pedal anyway.

Trevor.

[Trevor]

"Scott Dorsey" > wrote in message
...
> In article >,
> Arny Krueger > wrote:
>>"Kevin Aylward" > wrote in
>>message
>>> "Trevor" wrote in message
>>> u...
>>>
>>>
>>> "Scott Dorsey" >> wrote in message
>>>
>>>>> with exploded electrolytics the second
>>>
>>>> That's because of some VERY poor Chineses electro's
>>>> having been made for many years.
>>>
>>> It is not really a quality issue. Pretty much any
>>> electrolytic will explode if subjected to reverse
>>> polarity for long enough. Some of us used to do this
>>> deliberately when they were a lot younger.
>>
>>You've obviously not seen any of the results of the recent Chinese
>>electrolytic capacitor debacle. Parts that are properly installed and
>>operated well within their ratings will bulge or explode within a year of
>>being placed into service, if not sooner.
>
> This is true, but irrelevant to the original subject which was reversed
> polarity.
>
> When people reverse polarity on DC inputs, they tend to blow protection
> diodes and to blow up capacitors which weren't protected.
>
> Crappy Chinese (and Taiwanese) electrolytics made badly will fail without
> polarity reversal, but that's not the subject we were discussing.


Er wasn't it YOU (or was it Arny?) who stated "with exploded electrolytics
the second" (most common cause of equipment failure) ?
That is NOT just because of reverse polarity. It's because of POOR quality
electro's being SO common now.

Trevor.

[Trevor]

"Arny Krueger" > wrote in message
...
>>>>> And HOW does a 5A diode go "short circuit" as
>>>>> originally claimed, when connected to a plug pack?
>>>
>>> Scott described how this happens, with his usual
>>> exactness and attention to detail.
>>
>> NO he didn't. Please detail how YOU *Think* a small plug
>> pack can cause a 5A diode to go S/C.
>
> IME a wall wart that is rated at a few hunder mA won't damage a IN4001
> series diode in full forward conduction.

RIGHT. So the explanation was not his "usual exactness and attention to
detail" then. :-)

Trevor.

[Scott Dorsey]

Trevor > wrote:
>Er wasn't it YOU (or was it Arny?) who stated "with exploded electrolytics
>the second" (most common cause of equipment failure) ?
>That is NOT just because of reverse polarity. It's because of POOR quality
>electro's being SO common now.

NOBODY said that.

I said that, of the failures due to reverse polarity, most of them were
failures of protection diodes or of capacitors.

Stop putting words in my mouth. Go back and read what I posted.

I think this entire thread is the result of your misreading what other people
are saying.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Trevor]

"Scott Dorsey" > wrote in message
...
>>Er wasn't it YOU (or was it Arny?) who stated "with exploded electrolytics
>>the second" (most common cause of equipment failure) ?
>>That is NOT just because of reverse polarity. It's because of POOR quality
>>electro's being SO common now.
>
> NOBODY said that.

Right, YOU cut out the direct quote and claim nobody said it! :-)

Lets add it back again shall we.

----------
" > Honestly, this is the most common failure mode for consumer products
> receiving the wrong polarity, with exploded electrolytics the second"
----------


> I said that, of the failures due to reverse polarity, most of them were
> failures of protection diodes or of capacitors.

Nope, see actual quote above. I simply explained most exploded electro's
these days are NOT due to reverse polarity.


> Stop putting words in my mouth. Go back and read what I posted.

Done AND reposted above, after you felt the need to snip it BEFORE claiming
I am putting words in your mouth.
The trouble with trying to rewrite history on usenet is that you cannot
delete al copies.


> I think this entire thread is the result of your misreading what other
> people
> are saying.

Now that we can agree on at least.

Trevor.

[Trevor]

"Trevor" > wrote in message
u...
>> I think this entire thread is the result of your misreading what other
>> people are saying.
>
> Now that we can agree on at least.

****, I should have been clear here too that I mean *YOUR* (and others)
misreading of what *I* wrote originally.

Trevor.

[Scott Dorsey]

Trevor > wrote:
>"Scott Dorsey" > wrote in message
>Right, YOU cut out the direct quote and claim nobody said it! :-)
>
>Lets add it back again shall we.
>
>----------
>" > Honestly, this is the most common failure mode for consumer products
> > receiving the wrong polarity, with exploded electrolytics the second"
>----------

How do you parse that?

For consumer products receiving the wrong polarity
-- the most common failure mode is protection diode failure
-- the second most common is exploded electrolytics.

I don't understand WHERE you get any mention of exploded electrolytics
here in any context OTHER than in consumer electronics receiving the
wrong polarity.

>> I said that, of the failures due to reverse polarity, most of them were
>> failures of protection diodes or of capacitors.
>
>Nope, see actual quote above. I simply explained most exploded electro's
>these days are NOT due to reverse polarity.

Read that quote a few times until you understand what I said. It may help
to draw a sentence diagram.

>> Stop putting words in my mouth. Go back and read what I posted.
>
>Done AND reposted above, after you felt the need to snip it BEFORE claiming
>I am putting words in your mouth.

You have a severe reading comprehension problem here. Read that sentence
again.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Trevor]

"Scott Dorsey" > wrote in message
...
> Trevor > wrote:
>>"Scott Dorsey" > wrote in message
>>Right, YOU cut out the direct quote and claim nobody said it! :-)
>>
>>Lets add it back again shall we.
>>
>>----------
>>" > Honestly, this is the most common failure mode for consumer products
>> > receiving the wrong polarity, with exploded electrolytics the second"
>>----------
>
> How do you parse that?
>
> For consumer products receiving the wrong polarity
> -- the most common failure mode is protection diode failure
> -- the second most common is exploded electrolytics.


IF that is now your claim, then in my opinion you are WRONG.
If it is allowed to stand as written, then exploded electro's are indeed
right up there, and probably number one cause of consumer electronics
failure at the current time.


> I don't understand WHERE you get any mention of exploded electrolytics
> here in any context OTHER than in consumer electronics receiving the
> wrong polarity.

Because THAT is exactly the main cause of electro failure as I said, NOT
just incorrect polarity. Lets be real here, MOST devices that suffer from
electro failure are mains powered from an internal supply, and cannot
possibly fail due to the consumer connecting polarity wrong.
Your continued claims to the contrary simply make you look stupid.


>>> I said that, of the failures due to reverse polarity, most of them were
>>> failures of protection diodes or of capacitors.
>>
>>Nope, see actual quote above. I simply explained most exploded electro's
>>these days are NOT due to reverse polarity.
>
> Read that quote a few times until you understand what I said. It may help
> to draw a sentence diagram.

YOU may have thought you were restricting your statement as you now claim
(but for what reason God only knows) However you sure didn't WRITE it.


>>> Stop putting words in my mouth. Go back and read what I posted.
>>
>>Done AND reposted above, after you felt the need to snip it BEFORE
>>claiming
>>I am putting words in your mouth.
>
> You have a severe reading comprehension problem here. Read that sentence
> again.

Sure I can GUESS what you mean, however that does NOT make what I simply
added incorrect. If YOU think it does then YOU have the reading
comprehension problem.
In fact now placing such a limitation on your statement makes YOU incorrect,
since the biggest cause of failure in consumer electronics at the current
time in mine AND many others experience, is poor quality electro's which
have been correctly used as designed, and failed anyway!

And WHY the hell do you feel the need to go on and on about it? You'd save
more face by simply dropping the issue IMO. You sure aren't making yourself
look any smarter to the rest of the world!


Trevor.

[Scott Dorsey]

Trevor > wrote:
>"Scott Dorsey" > wrote in message
...
>> Trevor > wrote:
>>>"Scott Dorsey" > wrote in message
>>>Right, YOU cut out the direct quote and claim nobody said it! :-)
>>>
>>>Lets add it back again shall we.
>>>
>>>----------
>>>" > Honestly, this is the most common failure mode for consumer products
>>> > receiving the wrong polarity, with exploded electrolytics the second"
>>>----------
>>
>> How do you parse that?
>>
>> For consumer products receiving the wrong polarity
>> -- the most common failure mode is protection diode failure
>> -- the second most common is exploded electrolytics.
>
>
>IF that is now your claim, then in my opinion you are WRONG.
>If it is allowed to stand as written, then exploded electro's are indeed
>right up there, and probably number one cause of consumer electronics
>failure at the current time.

That's true but it has NOTHING to do with what I am saying. Read the
sentence again until you understand it.

>> I don't understand WHERE you get any mention of exploded electrolytics
>> here in any context OTHER than in consumer electronics receiving the
>> wrong polarity.
>
>Because THAT is exactly the main cause of electro failure as I said, NOT
>just incorrect polarity. Lets be real here, MOST devices that suffer from
>electro failure are mains powered from an internal supply, and cannot
>possibly fail due to the consumer connecting polarity wrong.
>Your continued claims to the contrary simply make you look stupid.

You are using an invalid argument called "asserting the contrapositive"
here. Please go back and read the sentence until you understand it.

I _only_ referred to the failures caused by reversed polarity. All
other failures are NOT the subject of the sentence and whether they
are not common has NOTHING to do with anything I said.

>YOU may have thought you were restricting your statement as you now claim
>(but for what reason God only knows) However you sure didn't WRITE it.

Go back and read the sentence again.

>And WHY the hell do you feel the need to go on and on about it? You'd save
>more face by simply dropping the issue IMO. You sure aren't making yourself
>look any smarter to the rest of the world!

Because I do not like having words put in my mouth by someone who has
incorrectly interpreted my statements and then goes on to claim to the
entire world that I said something else.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Trevor]

"Scott Dorsey" > wrote in message
...
>>IF that is now your claim, then in my opinion you are WRONG.
>>If it is allowed to stand as written, then exploded electro's are indeed
>>right up there, and probably number one cause of consumer electronics
>>failure at the current time.
>
> That's true but it has NOTHING to do with what I am saying. Read the
> sentence again until you understand it.

It has everything to do with what *I* said. Read what *I* said again until
YOU understand it.


> You are using an invalid argument called "asserting the contrapositive"
> here. Please go back and read the sentence until you understand it.

You are using an invalid argument called "arguing from the general to the
particular" Please go back and read what *I* wrote until you understand it!

> I _only_ referred to the failures caused by reversed polarity. All
> other failures are NOT the subject of the sentence and whether they
> are not common has NOTHING to do with anything I said.

Yes it does. Your claim is blatantly wrong IF only electro failures due to
reverse polarity are considered.


> Go back and read the sentence again.

You really are a stupid boring old fart that thinks putting others down
somehow boosts his stupid arguments. it doesn't.


>>And WHY the hell do you feel the need to go on and on about it? You'd save
>>more face by simply dropping the issue IMO. You sure aren't making
>>yourself
>>look any smarter to the rest of the world!
>
> Because I do not like having words put in my mouth by someone who has
> incorrectly interpreted my statements and then goes on to claim to the
> entire world that I said something else.

Nope, I simply added to your claim the REAL reason for most electro failure.
YOUR continued argument to the contrary is what is making you look a
complete moron to the rest of the world. You certainly don't need any help
from me!


Trevor.

[timewarp2008]

"Sam Trenholme" > wrote in message
...
> In article >,
> timewarp2008 > wrote:
>
>>your double-blind mumbo jumbo.
>
> With add due respect, I smell a troll. Or, more accurately, a crackpot.
> To wit:
>
> * This guy is using an anonymous account. Yeah, this is allowed in
> Usenet, but is not common; most other posters here (including myself)
> post with our real names.

Maybe you've never had the pleasure of a troll going real-world on
you, harrassing your clients and threatening your family. Good for
you.

> Or is his contributions to
> r.a.p consist of flaming anyone to a crisp who tells him that "if you
> can't hear the difference in a double blind test, then the difference
> can't be heard".

You already demonstrrated (and even admitted) that you didn't really
read that thread very carefully, and you were very politely chided for
it already, but once again, you show that you weren't paying
attention. I said nothing even resembling your misrepresentation.
Graham, the proudly cluless lackwit, went on for scores, even hundreds
of posts, waxing clueless on his "belief" that anything that can't be
heard in a double-blind test is absolutely bull****, and couldn't
possibly be a valid reason for selecting a microphone. He riffed on
this, ad nauseam. Actual professionals in the field mentioned such
factors as off-axis performance, reliability, known preferred
coloration, and a host of other reasons, even the simple business
reason that it can be profitable to meet a client's specifications if
they're willing to pay enough money. All of this went in one of
Graham's ears and out his nether orifice, while he insulted everyone
who disagreed with him (which included many of the best-informed
sources on the net), and he pontificated on the universal
applicability of double-blind, and the universal imagined bull****tery
of any and all other considerations, all based on his non-technical
fact-free "beliefs." He seems to thing that the value of cash in hand
is just a "placebo."

So now, he's advocated that someone else modify his equipment by
replacing a single diode with a full-wave bridge, for a host of
reasons which all fail the faith-based universal standard that he's
still spewing on that other thread. I pointed out that simple fact of
hypocrisy, and you jump to some conclusion that's reminiscent of some
of the strawmen that he has dreamt up.

I'm very familiar with double-blind comparisons, both what they're
good for, and what they're useless for. For more than a year, a while
back, the focus of my work was designing and carrying out double-blind
comparisons of various audio equipment, including designing a suite of
software to facilitate the gathering and analysis of subjective
assessment from dozens of listeners in such tests. I have a very good
idea what can and cannot be heard in a double-blind test. And, unlike
the comedy character that Billy plays on that other thread, I'm
familiar with a whole host of reasons for microphone selection that
can't be evaluated with double-blind testing. I'm a firm believer in
the known laws of physics and acoustics, and I've also run up against
the limits of oversimplified models to have a very good idea where
those limits lie. And I know who pays the bills. If you want to tilt
at imagined audiophool windmills, you're not going to get much action
by accusing me of saying things I never said. Audio religious
proseletyzers don't get much traction here; fortunately, they don't
seem to like the getting-hit-on-the-head lessons.

What you do with your killfilters is up to you, of course, but it
would be a lot more productive to killfile Bill Graham, who seems to
have no other life than to post thousands upon thousand of words of
utter bull**** trolling on a single thread, before I've even finished
making a single post. You say you've been around Usenet before; maybe
it was so long ago that you forgot the instructions to newbies that
you might want to read an entire thread before stepping in it. I do a
lot more reading here than posting, and if my occasional hobby of
calling trolls out for their trollery really bothers you, then
killfile away! I know that there are some who don't like me, but I do
have a pretty deep and broad history of experience in audio and music,
pro and otherwise. And I really don't give a flying fourier how he
hacks up his own cheezy M.I. equipment; if anyone needs idiot-proof
equipment it's him.

.... so meet Numpty Graham, the r.a.p. village idiot, whom you're
implicitly and perhaps unwittingly defending. I hope you enjoy his
kookdancing. Why don't you ask around about what people think of him?
You might find the answers more entertaining than the ones you'll get
about me.

[timewarp2008]

On Jan 10, 8:17*pm, (Scott Dorsey) wrote:
> Because I do not like having words put in my mouth by someone who has
> incorrectly interpreted my statements and then goes on to claim to the
> entire world that I said something else.
> --scott

Yeah, there's an awful lot of that sort of thing going around lately!

[Scott Dorsey]

Trevor > wrote:
>
>> I _only_ referred to the failures caused by reversed polarity. All
>> other failures are NOT the subject of the sentence and whether they
>> are not common has NOTHING to do with anything I said.
>
>Yes it does. Your claim is blatantly wrong IF only electro failures due to
>reverse polarity are considered.

My sentence specifically is talking about reverse polarity, since the
thread is about reverse polarity. And since the sentence begins
specifically referring to the case of reverse polarity. So, you would
think that I am talking only about reverse polarity, yes. Go back again
and read what I said.

>Nope, I simply added to your claim the REAL reason for most electro failure.

Yes, but this has absolutely nothing to do with the thread, which is about
reverse polarity. Go back again and read what I said.

>YOUR continued argument to the contrary is what is making you look a
>complete moron to the rest of the world. You certainly don't need any help
>from me!

I have never at any point argued the contrary, I only have argued that
these failures are irrelevant when the subject is reverse polarity. Go
back again and read what I said. You are putting words in my mouth again.
--scott

>
>
>Trevor.
>
>


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Bill Graham]

Scott Dorsey wrote:
> In article >,
> Sam Trenholme > wrote:
>>> I noted that you advised someone else to invest time and effort in
>>> modifying a piece of his sound equipment, not yours, with
>>> absolutely no evidence that you or anyone else would detect an
>>> improvement in a double-blind test.
>>
>> His suggestion is a modification to the power supply part of the
>> circuit. Not the audio part. His suggestion would make the device
>> in question more reliable; it's not to change its sound.
>
> In the case of a gain pedal where it may be one transistor, some
> resistors and a coupling capacitor, it's hard to break apart the
> power supply part and the audio part. Most of these things have no
> regulation, no constant current sources, and some of them even rely
> on transistor leakage for bias which is a no-no everywhere else in
> the world.
>
> You could argue this is an incompetent design, but then again if
> people like the way it sounds, who cares?
> --scott

For sure, these pedals are not, "professional equipment". I don't think I
would attempt to modify a very expensive piece of professional equipment. If
it costs in the thousand dollar and up range, I will send it back to the
manufacturer to be repaired, if for no other reason than to avoid destroying
my warrantee. But a guitar pedal? Give me a break. Even if I destroy it, I
could justify it on the basis of a learning experience.

[Sam Trenholme]

>> * This guy is using an anonymous account. Yeah, this is allowed in
>> Usenet, but is not common; most other posters here (including myself)
>> post with our real names.
>
>Maybe you've never had the pleasure of a troll going real-world on
>you, harassing your clients and threatening your family. Good for
>you.

No, I haven't had that, but I once had a troll attempt to contact my
employer to complain about me pointing out the guy was a pathological
liar. There's a reason I keep my current employment secret, and why my
mailing address is a PO box (actually, a "Mail Boxes etc." mailbox).

Yes, there are reasons to be anonymous, but it also means people will
more likely think you're trolling.

>Graham, the proudly clueless lack-wit,

It doesn't impress me that you're so bitter against this person. As I
just posted in another thread, it would be better to killfile him and go
on with your life.

>anything that can't be heard in a double-blind test is absolutely
>bull****

The thing is this: I put people who think double-blind is somehow
invalid in the same category as people who deny the moon landing. It's
not science, and it's self-dishonesty.

>he insulted everyone who disagreed with him

If I see him do that, I will consider killfiling him.

>what can and cannot be heard in a double-blind test
^^^^^^

(Google readers: I'm underlining the word "cannot")

Sorry, but I'm going to have to side with Bill here.

If it can not be heard in a double-blind test, it can not be heard. The
only exception I would make to that is the supposed "Hypersonic Effect"
that Oohashi keeps talking about in his papers, but, quite frankly, I'm
not going to believe it until someone besides Oohashi can reproduce the
results in a peer-reviewed paper.

There are a lot of makers of audio gear who make a good deal of money
having people doubt the validity of double-blind studies. Look at the
fan base for Super Audio CD, even though Meyer and Moran conclusively
showed that no one can hear the difference between a redbook CD and a
Super Audio CD (given good 16/44.1 converters) under normal
circumstances (Other studies have similar findings).

When the Meyer/Moran study came out, the lunatic fringe at sa-cd.net
went bonkers. They insulted Meyer and Moran every way they could,
trying desperately to put holes in the study. One common rant was "you
can't trust double-blind studies!".

>I know who pays the bills.

Exactly. There's, again, a lot of money to be made with people who
don't believe in double-blind studies. But, I find it very dishonest to
let money get in the way of facts.

>Audio religious proselytizers don't get much traction here;
>fortunately, they don't seem to like the getting-hit-on-the-head
>lessons.

My experience over the years is that this place is more friendly to
people who reject double-blind studies than, say, hydrogenaudio.org
(I've been posting here on and off since 1993).

>What you do with your killfilters is up to you

If it makes you feel any better, I've decided to not killfile you right
now. You seem interested enough in discourse; real trolls move on to
the next person to harass once they get killfiled by someone and could
care less whose killfile they are in.

>you forgot the instructions to newbies that you might want to read an
>entire thread before stepping in it.

Well, this thread has been around for about a month and my upstream's
retention is not that long. And, yes, I did look back in the thread as
far as I could. Then again, since I do run my own local Usenet feed
(leafnode is your friend), I will be able to retain threads for as long
as it fits in my partition for Usenet (over 3 gigs for a couple dozen of
newsgroups).

- Sam

--
#Sam Trenholme http://samiam.org -- Usenet user since September 1993#
######## My email address is at http://samiam.org/mailme.php ########
# The following script works around an annoyance in the Nano Editor #
cat | awk '{a=a $0 "\n";if($0 ~ /[a-zA-Z0-9]/){printf("%s",a);a=""}}'

[Gareth Magennis]

I did a quick test today on a couple of old wall warts I had lying around.
A 9v 500mA unregulated wall wart produced 3A through a 1N4007. A 9v
unregulated 1000mA wall wart produced 5 amps. I would guess 12v or 15v wall
warts would fare a lot better.

No fuses or wall warts were harmed in this brief experiment. :)


Gareth.

[Kevin Aylward[_4_]]

"timewarp2008" wrote in message
...


>I'm very familiar with double-blind comparisons, both what they're
>good for, and what they're useless for.

Such as?

Sure, if people like the look of something, irrespective of what it sounds
like, than that may be a basis for buying something. One local Blondie
tribute band around my way, has a decent mic cartridge in a standard
telephone handle, used for the start of "Hanging on the telephone". Looks
quite cool.

However, if the point is decide whether something is worth buying solely on
its technical merits, a double-blind test will tell you all you need to
know.

Kevin Aylward B.Sc.

www.kevinaylward.co.uk
"Live Long And Prosper \V/"

[Kevin Aylward[_4_]]

"Sam Trenholme" wrote in message ...


>>anything that can't be heard in a double-blind test is absolutely
>>bull****

>The thing is this: I put people who think double-blind is somehow
>invalid in the same category as people who deny the moon landing. It's
>not science, and it's self-dishonesty.

I agree.

I have an overall axiom that I use. Its the "No magic" axiom

http://www.kevinaylward.co.uk/replicators/magic.html

The world is pretty much how one actually sees it. There are no, gods,
pieces, pink unicorns, tea pots orbiting mars etc.

Kevin Aylward B.Sc.

www.kevinaylward.co.uk
"Live Long And Prosper \V/"

[RD Jones]

On Jan 11, 11:43*am, "Gareth Magennis" >
wrote:
> I did a quick test today on a couple of old wall warts I had lying around..
> A 9v 500mA unregulated wall wart produced 3A through a 1N4007. *A 9v
> unregulated 1000mA wall wart produced 5 amps. *I would guess 12v or 15v wall
> warts would fare a lot better.
>
> No fuses or wall warts were harmed in this brief experiment. *:)
>
> Gareth.

Yes, but was the diode harmed ?

rd

[Gareth Magennis]

"RD Jones" > wrote in message
...
> On Jan 11, 11:43 am, "Gareth Magennis" >
> wrote:
>> I did a quick test today on a couple of old wall warts I had lying
>> around.
>> A 9v 500mA unregulated wall wart produced 3A through a 1N4007. A 9v
>> unregulated 1000mA wall wart produced 5 amps. I would guess 12v or 15v
>> wall
>> warts would fare a lot better.
>>
>> No fuses or wall warts were harmed in this brief experiment. :)
>>
>> Gareth.
>
> Yes, but was the diode harmed ?
>
> rd


No, as the experiment was brief. I didn't want to destroy 2 potentially
useful wall warts to see which would melt first.

If anyone has enough time they could surely experiment with passing various
currents through the protection diodes typically found in guitar pedals, and
determine what currents and for for how long produce what results.
(They're cheap as chips - much cheaper than a fuse).

Me, I can't be arsed,


Gareth.

[Trevor]

"Gareth Magennis" > wrote in message
...
> No, as the experiment was brief. I didn't want to destroy 2 potentially
> useful wall warts to see which would melt first.

Unlike the designers, you didn't think it was a good idea to find out with
your equipment right? :-)


> If anyone has enough time they could surely experiment with passing
> various currents through the protection diodes typically found in guitar
> pedals, and determine what currents and for for how long produce what
> results. (They're cheap as chips - much cheaper than a fuse).

Only if the fuse is a glass type.

Trevor.

[Gareth Magennis]

"Trevor" > wrote in message
u...
>
> "Gareth Magennis" > wrote in message
> ...
>> No, as the experiment was brief. I didn't want to destroy 2 potentially
>> useful wall warts to see which would melt first.
>
> Unlike the designers, you didn't think it was a good idea to find out with
> your equipment right? :-)
>
>
>> If anyone has enough time they could surely experiment with passing
>> various currents through the protection diodes typically found in guitar
>> pedals, and determine what currents and for for how long produce what
>> results. (They're cheap as chips - much cheaper than a fuse).
>
> Only if the fuse is a glass type.
>
> Trevor.
>
>


Trevor, I'm sure most here have noticed by now your consistent and incessant
disingenuous posts.

You are, I believe, fundamentally dishonest, and I have no intention of
arguing with you.

[Bill Graham]

Sam Trenholme wrote:
>>> * This guy is using an anonymous account. Yeah, this is allowed in
>>> Usenet, but is not common; most other posters here (including
>>> myself) post with our real names.
>>
>> Maybe you've never had the pleasure of a troll going real-world on
>> you, harassing your clients and threatening your family. Good for
>> you.
>
> No, I haven't had that, but I once had a troll attempt to contact my
> employer to complain about me pointing out the guy was a pathological
> liar. There's a reason I keep my current employment secret, and why
> my mailing address is a PO box (actually, a "Mail Boxes etc."
> mailbox).
>
> Yes, there are reasons to be anonymous, but it also means people will
> more likely think you're trolling.
>
>> Graham, the proudly clueless lack-wit,
>
> It doesn't impress me that you're so bitter against this person. As I
> just posted in another thread, it would be better to killfile him and
> go on with your life.
>
>> anything that can't be heard in a double-blind test is absolutely
>> bull****
>
> The thing is this: I put people who think double-blind is somehow
> invalid in the same category as people who deny the moon landing.
> It's not science, and it's self-dishonesty.
>
>> he insulted everyone who disagreed with him
>
> If I see him do that, I will consider killfiling him.
>
>> what can and cannot be heard in a double-blind test
> ^^^^^^
>
> (Google readers: I'm underlining the word "cannot")
>
> Sorry, but I'm going to have to side with Bill here.
>
> If it can not be heard in a double-blind test, it can not be heard.
> The only exception I would make to that is the supposed "Hypersonic
> Effect" that Oohashi keeps talking about in his papers, but, quite
> frankly, I'm not going to believe it until someone besides Oohashi
> can reproduce the results in a peer-reviewed paper.
>
> There are a lot of makers of audio gear who make a good deal of money
> having people doubt the validity of double-blind studies. Look at the
> fan base for Super Audio CD, even though Meyer and Moran conclusively
> showed that no one can hear the difference between a redbook CD and a
> Super Audio CD (given good 16/44.1 converters) under normal
> circumstances (Other studies have similar findings).
>
> When the Meyer/Moran study came out, the lunatic fringe at sa-cd.net
> went bonkers. They insulted Meyer and Moran every way they could,
> trying desperately to put holes in the study. One common rant was
> "you can't trust double-blind studies!".
>
>> I know who pays the bills.
>
> Exactly. There's, again, a lot of money to be made with people who
> don't believe in double-blind studies. But, I find it very dishonest
> to let money get in the way of facts.
>
>> Audio religious proselytizers don't get much traction here;
>> fortunately, they don't seem to like the getting-hit-on-the-head
>> lessons.
>
> My experience over the years is that this place is more friendly to
> people who reject double-blind studies than, say, hydrogenaudio.org
> (I've been posting here on and off since 1993).
>
>> What you do with your killfilters is up to you
>
> If it makes you feel any better, I've decided to not killfile you
> right now. You seem interested enough in discourse; real trolls move
> on to the next person to harass once they get killfiled by someone
> and could care less whose killfile they are in.
>
>> you forgot the instructions to newbies that you might want to read an
>> entire thread before stepping in it.
>
> Well, this thread has been around for about a month and my upstream's
> retention is not that long. And, yes, I did look back in the thread
> as far as I could. Then again, since I do run my own local Usenet
> feed (leafnode is your friend), I will be able to retain threads for
> as long as it fits in my partition for Usenet (over 3 gigs for a
> couple dozen of newsgroups).
>
> - Sam

And, I have yet to insult anyone on this, or any other forum. If you read
the threads carefully, I think you'll find all the insults have been
directed at me by others.

[Bill Graham]

Gareth Magennis wrote:
> I did a quick test today on a couple of old wall warts I had lying
> around. A 9v 500mA unregulated wall wart produced 3A through a
> 1N4007. A 9v unregulated 1000mA wall wart produced 5 amps. I would
> guess 12v or 15v wall warts would fare a lot better.
>
> No fuses or wall warts were harmed in this brief experiment. :)
>

But was it a "quick double blind test"? :^)

[timewarp2008]

On Jan 11, 12:25*pm, Sam Trenholme >
wrote:

> There's, again, a lot of money to be made with people who
> don't believe in double-blind studies. *But, I find it very dishonest to
> let money get in the way of facts.
>
> >Audio religious proselytizers don't get much traction here;
> >fortunately, they don't seem to like the getting-hit-on-the-head
> >lessons.

Double-blind tests can be useful for comparing components that can be
quickly swapped in and out of an audio system without changing the
rest of the system. They produce subjective judgements about the
comparison of the components, and being double-blind, they can
eliminate judgments based on knowledge outside the realm of
audibility. But being comparison tests, they don't tell you about a
single component, which is often what is really needed. And they don't
produce hard objective facts such as can be had with careful
measurements, with calibrated test equipment, in a controlled
environment. I can measure the radiation pattern of a speaker system,
and get data from which I can produce both a series of polar plots for
every third-octave in the audio band, and a series of frequency
response plots for every five degrees in full horizontal and vertical
circles. I can learn significant things about speakers from this kind
of data. Measurements can yield a wealth of accurate understanding of
how a device responds, in ways that just aren't available in double-
blind tests. If you want simple repeatable and verifiable data about a
single component, not subjective opinions about comparisons, then
double-blind listening tests are not useful.

You can prove that audiomystics can't hear the difference between
ordinary large-gauge twisted-pair speaker cables and dilithium triple-
lutz wire with ibex hide insulation. You can show that suspending
gopher-wood icosahedrons and crysatl hockey pucks above your listening
position doesn't make the sound any less "veiled." Double-blind
comparisons, especially ABX tests, are great for identifying cases
where differences are not really perceptible. But in the real world of
professional sound reinforcement and recording, double-blind tests
have limited usefulness. Sometimes I bring more microphones than I
need to record a performance, and record extra tracks; and compare
them after the fact to decide which ones I like for the final product.
Double-blind comparisons can be useful in this type of decision
making. But I don't think double-blind tests are of much use when
configuring an array of speaker boxes for an outdoor festival stage,
although variations in the configuration of such arrays can have
clearly audible differences. Double-blind tests areng going to tell me
what kind of power a device requires, what kind of connectors I need,
what signal levels it can't handle, et pro-audio cetera.

Double-blind tests just aren't such a big deal in pro audio, for very
good reasons. One of the most important reasons is that they don't
give you repeatable objective data, which many professionals can
interpret accurately, quickly, and lucratively. The audiophool belief
that double-blind tests are invalid, as well as the other extreme
belief that they are all-knowing and all-seeing, are two faith-based
extremes, and the fact-based reality is not found at either of those
extremes. If you think that you can know all the audio and technical
characteristics about a piece of audio equipment from double-blind
listening comparisons, then you're talking religion, not science,
technology, or professional audio.Double-blind tests can be useful for
comparing components that can be quickly swapped in and out of an
audio system without changing the rest of the system. They produce
subjective judgements about the comparison of the components, and
being double-blind, they can eliminate judgments based on knowledge
outside the realm of audibility. But being comparison tests, they
don't tell you about a single component, which is often what is really
needed. And they don't produce hard objective facts such as can be had
with careful measurements, with calibrated test equipment, in a
controlled environment. I can measure the radiation pattern of a
speaker system, and get data from which I can produce both a series of
polar plots for every third-octave in the audio band, and a series of
frequency response plots for every five degrees in full horizontal and
vertical circles. I can learn significant things about speakers from
this kind of data. Measurements can yield a wealth of accurate
understanding of how a device responds, in ways that just aren't
available in double-blind tests. If you want simple repeatable and
verifiable data about a single component, not subjective opinions
about comparisons, then double-blind listening tests are not useful.

You can prove that audiomystics can't hear the difference between
ordinary large-gauge twisted-pair speaker cables and dilithium triple-
lutz wire with ibex hide insulation. You can show that suspending
gopher-wood icosahedrons and crysatl hockey pucks above your listening
position doesn't make the sound any less "veiled." Double-blind
comparisons, especially ABX tests, are great for identifying cases
where differences are not really perceptible. But in the real world of
professional sound reinforcement and recording, double-blind tests
have limited usefulness. Sometimes I bring more microphones than I
need to record a performance, and record extra tracks; and compare
them after the fact to decide which ones I like for the final product.
Double-blind comparisons can be useful in this type of decision
making. But I don't think double-blind tests are of much use when
configuring an array of speaker boxes for an outdoor festival stage,
although variations in the configuration of such arrays can have
clearly audible differences. Double-blind tests areng going to tell me
what kind of power a device requires, what kind of connectors I need,
what signal levels it can't handle, et pro-audio cetera.

Double-blind tests just aren't such a big deal in pro audio, for very
good reasons. One of the most important reasons is that they don't
give you repeatable objective data, which many professionals can
interpret accurately, quickly, and lucratively. The audiophool belief
that double-blind tests are invalid, as well as the other extreme
belief that they are all-knowing and all-seeing, are two faith-based
extremes, and the fact-based reality is not found at either of those
extremes. If you think that you can know all the audio and technical
characteristics about a piece of audio equipment from double-blind
listening comparisons, then you're talking religion, not science,
technology, or professional audio.Double-blind tests can be useful for
comparing components that can be quickly swapped in and out of an
audio system without changing the rest of the system. They produce
subjective judgements about the comparison of the components, and
being double-blind, they can eliminate judgments based on knowledge
outside the realm of audibility. But being comparison tests, they
don't tell you about a single component, which is often what is really
needed. And they don't produce hard objective facts such as can be had
with careful measurements, with calibrated test equipment, in a
controlled environment. I can measure the radiation pattern of a
speaker system, and get data from which I can produce both a series of
polar plots for every third-octave in the audio band, and a series of
frequency response plots for every five degrees in full horizontal and
vertical circles. I can learn significant things about speakers from
this kind of data. Measurements can yield a wealth of accurate
understanding of how a device responds, in ways that just aren't
available in double-blind tests. If you want simple repeatable and
verifiable data about a single component, not subjective opinions
about comparisons, then double-blind listening tests are not useful.

You can prove that audiomystics can't hear the difference between
ordinary large-gauge twisted-pair speaker cables and dilithium triple-
lutz wire with ibex hide insulation. You can show that suspending
gopher-wood icosahedrons and crysatl hockey pucks above your listening
position doesn't make the sound any less "veiled." Double-blind
comparisons, especially ABX tests, are great for identifying cases
where differences are not really perceptible. But in the real world of
professional sound reinforcement and recording, double-blind tests
have limited usefulness. Sometimes I bring more microphones than I
need to record a performance, and record extra tracks; and compare
them after the fact to decide which ones I like for the final product.
Double-blind comparisons can be useful in this type of decision
making. But I don't think double-blind tests are of much use when
configuring an array of speaker boxes for an outdoor festival stage,
although variations in the configuration of such arrays can have
clearly audible differences. Double-blind tests areng going to tell me
what kind of power a device requires, what kind of connectors I need,
what signal levels it can't handle, et pro-audio cetera.

Double-blind tests just aren't such a big deal in pro audio, for very
good reasons. One of the most important reasons is that they don't
give you repeatable objective data, which many professionals can
interpret accurately, quickly, and lucratively. The audiophool belief
that double-blind tests are invalid, as well as the other extreme
belief that they are all-knowing and all-seeing, are two faith-based
extremes, and the fact-based reality is not found at either of those
extremes. If you think that you can know all the audio and technical
characteristics about a piece of audio equipment from double-blind
listening comparisons, then you're talking religion, not science,
technology, or professional audio.Double-blind tests can be useful for
comparing components that can be quickly swapped in and out of an
audio system without changing the rest of the system. They produce
subjective judgements about the comparison of the components, and
being double-blind, they can eliminate judgments based on knowledge
outside the realm of audibility. But being comparison tests, they
don't tell you about a single component, which is often what is really
needed. And they don't produce hard objective facts such as can be had
with careful measurements, with calibrated test equipment, in a
controlled environment. I can measure the radiation pattern of a
speaker system, and get data from which I can produce both a series of
polar plots for every third-octave in the audio band, and a series of
frequency response plots for every five degrees in full horizontal and
vertical circles. I can learn significant things about speakers from
this kind of data. Measurements can yield a wealth of accurate
understanding of how a device responds, in ways that just aren't
available in double-blind tests. If you want simple repeatable and
verifiable data about a single component, not subjective opinions
about comparisons, then double-blind listening tests are not useful.

You can prove that audiomystics can't hear the difference between
ordinary large-gauge twisted-pair speaker cables and dilithium triple-
lutz wire with ibex hide insulation. You can show that suspending
gopher-wood icosahedrons and crysatl hockey pucks above your listening
position doesn't make the sound any less "veiled." Double-blind
comparisons, especially ABX tests, are great for identifying cases
where differences are not really perceptible. But in the real world of
professional sound reinforcement and recording, double-blind tests
have limited usefulness. Sometimes I bring more microphones than I
need to record a performance, and record extra tracks; and compare
them after the fact to decide which ones I like for the final product.
Double-blind comparisons can be useful in this type of decision
making. But I don't think double-blind tests are of much use when
configuring an array of speaker boxes for an outdoor festival stage,
although variations in the configuration of such arrays can have
clearly audible differences. Double-blind tests areng going to tell me
what kind of power a device requires, what kind of connectors I need,
what signal levels it can't handle, et pro-audio cetera.

Double-blind tests just aren't such a big deal in pro audio, for very
good reasons. One of the most important reasons is that they don't
give you repeatable objective data, which many professionals can
interpret accurately, quickly, and lucratively. The audiophool belief
that double-blind tests are invalid, as well as the other extreme
belief that they are all-knowing and all-seeing, are two faith-based
extremes, and the fact-based reality is not found at either of those
extremes. If you think that you can know all the audio and technical
characteristics about a piece of audio equipment from double-blind
listening comparisons, then you're talking religion, not science,
technology, or professional audio.Double-blind tests can be useful for
comparing components that can be quickly swapped in and out of an
audio system without changing the rest of the system. They produce
subjective judgements about the comparison of the components, and
being double-blind, they can eliminate judgments based on knowledge
outside the realm of audibility. But being comparison tests, they
don't tell you about a single component, which is often what is really
needed. And they don't produce hard objective facts such as can be had
with careful measurements, with calibrated test equipment, in a
controlled environment. I can measure the radiation pattern of a
speaker system, and get data from which I can produce both a series of
polar plots for every third-octave in the audio band, and a series of
frequency response plots for every five degrees in full horizontal and
vertical circles. I can learn significant things about speakers from
this kind of data. Measurements can yield a wealth of accurate
understanding of how a device responds, in ways that just aren't
available in double-blind tests. If you want simple repeatable and
verifiable data about a single component, not subjective opinions
about comparisons, then double-blind listening tests are not useful.

You can prove that audiomystics can't hear the difference between
ordinary large-gauge twisted-pair speaker cables and dilithium triple-
lutz wire with ibex hide insulation. You can show that suspending
gopher-wood icosahedrons and crysatl hockey pucks above your listening
position doesn't make the sound any less "veiled." Double-blind
comparisons, especially ABX tests, are great for identifying cases
where differences are not really perceptible. But in the real world of
professional sound reinforcement and recording, double-blind tests
have limited usefulness. Sometimes I bring more microphones than I
need to record a performance, and record extra tracks; and compare
them after the fact to decide which ones I like for the final product.
Double-blind comparisons can be useful in this type of decision
making. But I don't think double-blind tests are of much use when
configuring an array of speaker boxes for an outdoor festival stage,
although variations in the configuration of such arrays can have
clearly audible differences. Double-blind tests areng going to tell me
what kind of power a device requires, what kind of connectors I need,
what signal levels it can't handle, et pro-audio cetera.

Double-blind tests just aren't such a big deal in pro audio, for very
good reasons. One of the most important reasons is that they don't
give you repeatable objective data, which many professionals can
interpret accurately, quickly, and lucratively. The audiophool belief
that double-blind tests are invalid, as well as the other extreme
belief that they are all-knowing and all-seeing, are two faith-based
extremes, and the fact-based reality is not found at either of those
extremes. If you think that you can know all the audio and technical
characteristics about a piece of audio equipment from double-blind
listening comparisons, then you're talking religion, not science,
technology, or professional audio.Double-blind tests can be useful for
comparing components that can be quickly swapped in and out of an
audio system without changing the rest of the system. They produce
subjective judgements about the comparison of the components, and
being double-blind, they can eliminate judgments based on knowledge
outside the realm of audibility. But being comparison tests, they
don't tell you about a single component, which is often what is really
needed. And they don't produce hard objective facts such as can be had
with careful measurements, with calibrated test equipment, in a
controlled environment. I can measure the radiation pattern of a
speaker system, and get data from which I can produce both a series of
polar plots for every third-octave in the audio band, and a series of
frequency response plots for every five degrees in full horizontal and
vertical circles. I can learn significant things about speakers from
this kind of data. Measurements can yield a wealth of accurate
understanding of how a device responds, in ways that just aren't
available in double-blind tests. If you want simple repeatable and
verifiable data about a single component, not subjective opinions
about comparisons, then double-blind listening tests are not useful.

You can prove that audiomystics can't hear the difference between
ordinary large-gauge twisted-pair speaker cables and dilithium triple-
lutz wire with ibex hide insulation. You can show that suspending
gopher-wood icosahedrons and crysatl hockey pucks above your listening
position doesn't make the sound any less "veiled." Double-blind
comparisons, especially ABX tests, are great for identifying cases
where differences are not really perceptible. But in the real world of
professional sound reinforcement and recording, double-blind tests
have limited usefulness. Sometimes I bring more microphones than I
need to record a performance, and record extra tracks; and compare
them after the fact to decide which ones I like for the final product.
Double-blind comparisons can be useful in this type of decision
making. But I don't think double-blind tests are of much use when
configuring an array of speaker boxes for an outdoor festival stage,
although variations in the configuration of such arrays can have
clearly audible differences. Double-blind tests areng going to tell me
what kind of power a device requires, what kind of connectors I need,
what signal levels it can't handle, et pro-audio cetera.

Double-blind tests just aren't such a big deal in pro audio, for very
good reasons. One of the most important reasons is that they don't
give you repeatable objective data, which many professionals can
interpret accurately, quickly, and lucratively. The audiophool belief
that double-blind tests are invalid, as well as the other extreme
belief that they are all-knowing and all-seeing, are two faith-based
extremes, and the fact-based reality is not found at either of those
extremes. If you think that you can know all the audio and technical
characteristics about a piece of audio equipment from double-blind
listening comparisons, then you're talking religion, not science,
technology, or professional audio.Double-blind tests can be useful for
comparing components that can be quickly swapped in and out of an
audio system without changing the rest of the system. They produce
subjective judgements about the comparison of the components, and
being double-blind, they can eliminate judgments based on knowledge
outside the realm of audibility. But being comparison tests, they
don't tell you about a single component, which is often what is really
needed. And they don't produce hard objective facts such as can be had
with careful measurements, with calibrated test equipment, in a
controlled environment. I can measure the radiation pattern of a
speaker system, and get data from which I can produce both a series of
polar plots for every third-octave in the audio band, and a series of
frequency response plots for every five degrees in full horizontal and
vertical circles. I can learn significant things about speakers from
this kind of data. Measurements can yield a wealth of accurate
understanding of how a device responds, in ways that just aren't
available in double-blind tests. If you want simple repeatable and
verifiable data about a single component, not subjective opinions
about comparisons, then double-blind listening tests are not useful.

You can prove that audiomystics can't hear the difference between
ordinary large-gauge twisted-pair speaker cables and dilithium triple-
lutz wire with ibex hide insulation. You can show that suspending
gopher-wood icosahedrons and crysatl hockey pucks above your listening
position doesn't make the sound any less "veiled." Double-blind
comparisons, especially ABX tests, are great for identifying cases
where differences are not really perceptible. But in the real world of
professional sound reinforcement and recording, double-blind tests
have limited usefulness. Sometimes I bring more microphones than I
need to record a performance, and record extra tracks; and compare
them after the fact to decide which ones I like for the final product.
Double-blind comparisons can be useful in this type of decision
making. But I don't think double-blind tests are of much use when
configuring an array of speaker boxes for an outdoor festival stage,
although variations in the configuration of such arrays can have
clearly audible differences. Double-blind tests areng going to tell me
what kind of power a device requires, what kind of connectors I need,
what signal levels it can't handle, et pro-audio cetera.

Double-blind tests just aren't such a big deal in pro audio, for very
good reasons. One of the most important reasons is that they don't
give you repeatable objective data, which many professionals can
interpret accurately, quickly, and lucratively. The audiophool belief
that double-blind tests are invalid, as well as the other extreme
belief that they are all-knowing and all-seeing, are two faith-based
extremes, and the fact-based reality is not found at either of those
extremes. If you think that you can know all the audio and technical
characteristics about a piece of audio equipment from double-blind
listening comparisons, then you're talking religion, not science,
technology, or professional audio.Double-blind tests can be useful for
comparing components that can be quickly swapped in and out of an
audio system without changing the rest of the system. They produce
subjective judgements about the comparison of the components, and
being double-blind, they can eliminate judgments based on knowledge
outside the realm of audibility. But being comparison tests, they
don't tell you about a single component, which is often what is really
needed. And they don't produce hard objective facts such as can be had
with careful measurements, with calibrated test equipment, in a
controlled environment. I can measure the radiation pattern of a
speaker system, and get data from which I can produce both a series of
polar plots for every third-octave in the audio band, and a series of
frequency response plots for every five degrees in full horizontal and
vertical circles. I can learn significant things about speakers from
this kind of data. Measurements can yield a wealth of accurate
understanding of how a device responds, in ways that just aren't
available in double-blind tests. If you want simple repeatable and
verifiable data about a single component, not subjective opinions
about comparisons, then double-blind listening tests are not useful.

You can prove that audiomystics can't hear the difference between
ordinary large-gauge twisted-pair speaker cables and dilithium triple-
lutz wire with ibex hide insulation. You can show that suspending
gopher-wood icosahedrons and crysatl hockey pucks above your listening
position doesn't make the sound any less "veiled." Double-blind
comparisons, especially ABX tests, are great for identifying cases
where differences are not really perceptible. But in the real world of
professional sound reinforcement and recording, double-blind tests
have limited usefulness. Sometimes I bring more microphones than I
need to record a performance, and record extra tracks; and compare
them after the fact to decide which ones I like for the final product.
Double-blind comparisons can be useful in this type of decision
making. But I don't think double-blind tests are of much use when
configuring an array of speaker boxes for an outdoor festival stage,
although variations in the configuration of such arrays can have
clearly audible differences. Double-blind tests areng going to tell me
what kind of power a device requires, what kind of connectors I need,
what signal levels it can't handle, et pro-audio cetera.

Double-blind tests just aren't such a big deal in pro audio, for very
good reasons. One of the most important reasons is that they don't
give you repeatable objective data, which many professionals can
interpret accurately, quickly, and lucratively. The audiophool belief
that double-blind tests are invalid, as well as the other extreme
belief that they are all-knowing and all-seeing, are two faith-based
extremes, and the fact-based reality is not found at either of those
extremes. If you think that you can know all the audio and technical
characteristics about a piece of audio equipment from double-blind
listening comparisons, then you're talking religion, not science,
technology, or professional audio.Double-blind tests can be useful for
comparing components that can be quickly swapped in and out of an
audio system without changing the rest of the system. They produce
subjective judgements about the comparison of the components, and
being double-blind, they can eliminate judgments based on knowledge
outside the realm of audibility. But being comparison tests, they
don't tell you about a single component, which is often what is really
needed. And they don't produce hard objective facts such as can be had
with careful measurements, with calibrated test equipment, in a
controlled environment. I can measure the radiation pattern of a
speaker system, and get data from which I can produce both a series of
polar plots for every third-octave in the audio band, and a series of
frequency response plots for every five degrees in full horizontal and
vertical circles. I can learn significant things about speakers from
this kind of data. Measurements can yield a wealth of accurate
understanding of how a device responds, in ways that just aren't
available in double-blind tests. If you want simple repeatable and
verifiable data about a single component, not subjective opinions
about comparisons, then double-blind listening tests are not useful.

You can prove that audiomystics can't hear the difference between
ordinary large-gauge twisted-pair speaker cables and dilithium triple-
lutz wire with ibex hide insulation. You can show that suspending
gopher-wood icosahedrons and crysatl hockey pucks above your listening
position doesn't make the sound any less "veiled." Double-blind
comparisons, especially ABX tests, are great for identifying cases
where differences are not really perceptible. But in the real world of
professional sound reinforcement and recording, double-blind tests
have limited usefulness. Sometimes I bring more microphones than I
need to record a performance, and record extra tracks; and compare
them after the fact to decide which ones I like for the final product.
Double-blind comparisons can be useful in this type of decision
making. But I don't think double-blind tests are of much use when
configuring an array of speaker boxes for an outdoor festival stage,
although variations in the configuration of such arrays can have
clearly audible differences. Double-blind tests areng going to tell me
what kind of power a device requires, what kind of connectors I need,
what signal levels it can't handle, et pro-audio cetera.

Double-blind tests just aren't such a big deal in pro audio, for very
good reasons. One of the most important reasons is that they don't
give you repeatable objective data, which many professionals can
interpret accurately, quickly, and lucratively. The audiophool belief
that double-blind tests are completely invalid, as well as the other
extreme belief that double-blind tests are all-knowing and all-seeing,
are two faith-based extremes, and the fact-based reality is not found
at either of those extremes. If you think that you can know all the
audio and technical characteristics about a piece of audio equipment
from double-blind listening comparisons, then you're talking religion,
not science, technology, or professional audio.

[timewarp2008]

On Jan 11, 7:15*pm, "Numpty Graham" > wrote:
> And, I have yet to insult anyone on this, or any other forum. If you read
> the threads carefully, I think you'll find all the insults have been
> directed at me by others.-

If you read the threads carefully, you can see how far up his asshole
Numpty's head must be to tell such a whopper!

[timewarp2008]

On Jan 12, 4:41*pm, timewarp2008 > wrote:
> <sneck>

Oops. Mea culpa. Sorry about the egregious multi-paste. My CTRL-V must
have gotten stuck, and I was at fault for not taking care to read what
I had pasted and posted.

[Trevor]

"Gareth Magennis" > wrote in message
...
>>> If anyone has enough time they could surely experiment with passing
>>> various currents through the protection diodes typically found in guitar
>>> pedals, and determine what currents and for for how long produce what
>>> results. (They're cheap as chips - much cheaper than a fuse).
>>
>> Only if the fuse is a glass type.

> Trevor, I'm sure most here have noticed by now your consistent and
> incessant disingenuous posts.
>
> You are, I believe, fundamentally dishonest, and I have no intention of
> arguing with you.

Good! I'm sure intelligent people don't claim a piece of fuse wire is
necessarily more expensive than a diode, and pretend anyone who thinks
otherwise is "fundamentaly dishonest". But you are welcome to your
delusions, I have no intention of arguing with morons any more either!
That's what kill files were invented for. I will not feel at all upset if
you choose to use it, as I will!

Trevor.

[Kevin Aylward[_4_]]

"timewarp2008" wrote in message
...

On Jan 11, 12:25 pm, Sam Trenholme >
wrote:

> There's, again, a lot of money to be made with people who
> don't believe in double-blind studies. But, I find it very dishonest to
> let money get in the way of facts.
>
> >Audio religious proselytizers don't get much traction here;
> >fortunately, they don't seem to like the getting-hit-on-the-head
> >lessons.

>And they don't
>produce hard objective facts such as can be had with careful
>measurements, with calibrated test equipment, in a controlled
environment>. I can measure the radiation pattern of a speaker system,
>and get data from which I can produce both a series of polar plots for
>every third-octave in the audio band, and a series of frequency
>response plots for every five degrees in full horizontal and vertical
>circles. I can learn significant things about speakers from this kind
>
>of data. Measurements can yield a wealth of accurate understanding of
>how a device responds, in ways that just aren't available in double-
>blind tests. If you want simple repeatable and verifiable data about a
>single component, not subjective opinions about comparisons, then
>double-blind listening tests are not useful.

I pretty much agree with all of this, and the bits sniped for brevity. I
would say that this is discussing a different aspect of the debate that was
really not being addressed in this context. Yes, double blind tests, by its
nature can only address subjective issues. A double blind test does not use
measuring equipment, so by construction, is not addressing detailed
objective issues.

I will say that if I am designing a general power amplifier, I see
absolutely no reason whatsoever to ever listen to it until it is quite
finished and ready for sale. The technical specifications is quite
sufficient. It is relatively straightforward to design an amplifier that is
a "straight piece of wire with gain".


Kevin Aylward B.Sc.
www.kevinaylward.co.uk

[Trevor]

"Kevin Aylward" > wrote in message
...
> I will say that if I am designing a general power amplifier, I see
> absolutely no reason whatsoever to ever listen to it until it is quite
> finished and ready for sale. The technical specifications is quite
> sufficient. It is relatively straightforward to design an amplifier that
> is a "straight piece of wire with gain".

Of course, unfortunately the subjectivists will argue forever about how
different types of wire affect the sound, whether with or without gain, and
straight or not! :-)

Trevor.

[William Sommerwerck]

> It is relatively straightforward to design an amplifier
> that is a "straight piece of wire with gain".

Perhaps it is. What are your design criteria?

[Arny Krueger]

"William Sommerwerck" > wrote in
message
>> It is relatively straightforward to design an amplifier
>> that is a "straight piece of wire with gain".

> Perhaps it is. What are your design criteria?

The usual answer is gain, input impedance, noise, nonlinear distortion at
all relevant frequencies, linear distortion, including for power amps: Their
performance into low impedance, nonlinear, and reactive loads. On the AC
supply side, power factor.

[William Sommerwerck]

"Arny Krueger" > wrote in message
...
> "William Sommerwerck" > wrote in
> message

>>> It is relatively straightforward to design an amplifier
>>> that is a "straight piece of wire with gain".

>> Perhaps it is. What are your design criteria?

> The usual answer is gain, input impedance, noise, nonlinear
> distortion at all relevant frequencies, linear distortion, including
> for power amps: Their performance into low impedance, nonlinear,
> and reactive loads. On the AC supply side, power factor.

We've argued this before, and those criteria are certainly pertinent. No one
would design an amplifier without considering all of them. (Gerry Stanley
famously said that the reason the DC-300A sounded better than the DC-300 was
that he hadn't paid attention to the earlier amplifier's behavior with
reactive loads.)

I ask the following, hoping you will carefully consider it before
responding... How do you know that reducing harmonic and IM distortion to
extremely low levels with test signals necessarily produces a comparable
reduction in such distortions with program material? In a broader sense, how
do you know that an amplifier's behavior with a complex signal (ie, music)
is accurately predicted by its behavior with simple signals?

To the best of my knowledge, only QUAD and Crown have investigated this
question. An ex-Crown employee told me they could get a 90dB (!!!) null
between input and output on the Power Line amplifiers (which are no longer
made) with program material. One might reasonably assume that such an
amplifier would not subjectively alter the sound in any way.

Of course, Gerry Stanley also designed the K-series switching amps (also no
longer made) which are the worst-sounding amps I've ever heard, so bad you
don't even need to compare them with anything else to hear their
wretchedness. Yet they measure extremely well on lab tests.

I've owned amps designed by Dan D'Agostino and John Curl, which measure
beautifully, but sound quite different. There's no question that there's
something measurably different about them -- but no one wants to put out the
effort to find out what it is.

[Arny Krueger]

"William Sommerwerck" > wrote in
message
> "Arny Krueger" > wrote in message
> ...
>> "William Sommerwerck" > wrote
>> in
>> message
>
>>>> It is relatively straightforward to design an amplifier
>>>> that is a "straight piece of wire with gain".
>
>>> Perhaps it is. What are your design criteria?
>
>> The usual answer is gain, input impedance, noise,
>> nonlinear distortion at all relevant frequencies, linear
>> distortion, including for power amps: Their performance
>> into low impedance, nonlinear, and reactive loads. On
>> the AC supply side, power factor.
>
> We've argued this before, and those criteria are
> certainly pertinent. No one would design an amplifier
> without considering all of them. (Gerry Stanley famously
> said that the reason the DC-300A sounded better than the
> DC-300 was that he hadn't paid attention to the earlier
> amplifier's behavior with reactive loads.)

That is a well-known story. The modest SOA performance of the DC 300 was the
result of the relatively poor SOA performance of the output devices at hand.
At the point of design, nobody knew for sure what the customer operational
environment actually was. The first time they stuck their toes into the
water they found out! Ouch!!!

Hence my comments about : "Their performance
into low impedance, nonlinear, and reactive loads."


> I ask the following, hoping you will carefully consider
> it before responding... How do you know that reducing
> harmonic and IM distortion to extremely low levels with
> test signals necessarily produces a comparable reduction
> in such distortions with program material?

Hmm, I did my first amplifer bench measurements when I was 13. That was over
50 years, and a lot of time spent on the bench and in relevant university
classes ago.

Both the theory and the practice say that if you do everything right it
works.

> In a broader
> sense, how do you know that an amplifier's behavior with
> a complex signal (ie, music) is accurately predicted by
> its behavior with simple signals?

Oh, that is simple. You test the amplifier with complex signals. There are
ways to test equipment for both nonlinear and linear distoriton using
regular music as your test signals.

Also, if 1 or 2 sine wave(s) is the classic simple test signal, then a
test signal composed of 30+ of them should be at least a little more
complex, right? The results of tests with 1-2 sine waves, 30+ sine waves,
and actual real world music converge very nicely, thank you!

> To the best of my knowledge, only QUAD and Crown have
> investigated this question.

Speaks to your lack of knowlege and memory.

> An ex-Crown employee told me
> they could get a 90dB (!!!) null between input and output
> on the Power Line amplifiers (which are no longer made)
> with program material.

That would be consistent with my own bench observations. However, I
distrust nulling approaches like that for reasons I've gone over many times
on public forums including probably this one.

> One might reasonably assume that
> such an amplifier would not subjectively alter the sound
> in any way.

I don't think I've done any DBTs on those exact amplifiers, but I have
tested equipment that measured worse, and its output was indistinguishable
from its input, when the two were level matched.

> Of course, Gerry Stanley also designed the K-series
> switching amps (also no longer made) which are the
> worst-sounding amps I've ever heard, so bad you don't
> even need to compare them with anything else to hear
> their wretchedness. Yet they measure extremely well on
> lab tests.

Ditto above.

> I've owned amps designed by Dan D'Agostino and John Curl,
> which measure beautifully, but sound quite different.

Given your well-known lack of expertise and patience to what is considered
to be a proper listening test in the circles I travel, any of your comments
about ampliier sound are taken with a huge shaker of salt.

> There's no question that there's something measurably
> different about them -- but no one wants to put out the
> effort to find out what it is.

We've never been able to fix your head. ;-)

[geoff]

Kevin Aylward wrote:

> I pretty much agree with all of this, and the bits sniped for
> brevity. I would say that this is discussing a different aspect of
> the debate that was really not being addressed in this context. Yes,
> double blind tests, by its nature can only address subjective issues.
> A double blind test does not use measuring equipment, so by
> construction, is not addressing detailed objective issues.

Those 'subjective issues' may in fact be objective issues relating to
aspects not covered by your beloved specs.

geoff

[Scott Dorsey]

In article >,
William Sommerwerck > wrote:
>> It is relatively straightforward to design an amplifier
>> that is a "straight piece of wire with gain".
>
>Perhaps it is. What are your design criteria?

I don't know about his, but one of mine is that it should not catch fire
when driving a 2uF capacitive load like a Quad ESL....
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[William Sommerwerck]

>>> It is relatively straightforward to design an amplifier
>>> that is a "straight piece of wire with gain".

>> Perhaps it is. What are your design criteria?

> I don't know about his, but one of mine is that it should
> not catch fire when driving a 2uF capacitive load like a
> Quad ESL...

Have you experienced this? <grin>

[Scott Dorsey]

geoff > wrote:
>Kevin Aylward wrote:
>
>> I pretty much agree with all of this, and the bits sniped for
>> brevity. I would say that this is discussing a different aspect of
>> the debate that was really not being addressed in this context. Yes,
>> double blind tests, by its nature can only address subjective issues.
>> A double blind test does not use measuring equipment, so by
>> construction, is not addressing detailed objective issues.
>
>Those 'subjective issues' may in fact be objective issues relating to
>aspects not covered by your beloved specs.

In the case of things like pedals and mixing consoles where 90% of the
system is the user interface, the subjective issues are often the most
important part of the system evaluation.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Scott Dorsey]

William Sommerwerck > wrote:
>>>> It is relatively straightforward to design an amplifier
>>>> that is a "straight piece of wire with gain".
>
>>> Perhaps it is. What are your design criteria?
>
>> I don't know about his, but one of mine is that it should
>> not catch fire when driving a 2uF capacitive load like a
>> Quad ESL...
>
>Have you experienced this? <grin>

With several different amps, some of them with good reputations from
seemingly-reputable companies. You'd think people would keep track of
where their poles and zeros were going, but no.

Although the absolute best amplifier failure I have ever seen was when
I was recording some band at the Little Five Points Pub in Atlanta
and the Phase Linear in the house sound system started spitting sparks
four or five feet into the air, accompanied by very loud hum.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Doug McDonald[_4_]]

On 1/18/2011 6:47 AM, Arny Krueger wrote:

>
>> An ex-Crown employee told me
>> they could get a 90dB (!!!) null between input and output
>> on the Power Line amplifiers (which are no longer made)
>> with program material.
>
> That would be consistent with my own bench observations. However, I
> distrust nulling approaches like that for reasons I've gone over many times
> on public forums including probably this one.
>
>

I'd be interested in hearing ... again ... why you think that. We assume
a real speaker load on the power amp, in the same room (thus, microphonics
are included in the test.)

Doug McDonald

[PStamler]

On Jan 18, 4:47*pm, Doug McDonald
> wrote:
> On 1/18/2011 6:47 AM, Arny Krueger wrote:
>
>
>
> >> An ex-Crown employee told me
> >> they could get a 90dB (!!!) null between input and output
> >> on the Power Line amplifiers (which are no longer made)
> >> with program material.
>
> > That would be consistent with my own bench observations. However, I
> > distrust nulling approaches like that for reasons I've gone over many times
> > on public forums including probably this one.
>
> I'd be interested in hearing ... again ... why you think that. We assume
> a real speaker load on the power amp, in the same room (thus, microphonics
> are included in the test.)

I'm not Arny, but will jump in anyway.

The problem with nulling tests is that they privilege one type of
performance over another. Unless the amplifier has very wide
bandwiidth, phase shifts at the top and the bottom will show up as
sizeable error. In a straight-wire nulling test, a wideband amplifier
with high distortion will typically null better than a narrower-band
amplifier with very low distortion.

I'm not going to get into the question of whether phase shifts at
frequency extremes are audible. What I'm saying, rather, is that
straight-wire null tests privilege phase shifts above all other errors
to such a great extent that they are effectively useless.

Peter Walker proposed "crooked-wire" bypass and null tests, in which
the alternative path had the same phase-shift characteristics as the
amplifier. It turned out to be very difficult to implement; the
compensation network for one amplifier had about 16 components, and
the null went away whenever the amp's temperature changed, as it
invariably did when the amp played.

In short, null tests are too sensitive to one parameter of dubious
audibility, to the extent that other parameters are swamped.

Peace,
Paul

[Arny Krueger]

"Doug McDonald" >
wrote in message
> On 1/18/2011 6:47 AM, Arny Krueger wrote:
>
>>
>>> An ex-Crown employee told me
>>> they could get a 90dB (!!!) null between input and
>>> output on the Power Line amplifiers (which are no
>>> longer made) with program material.
>>
>> That would be consistent with my own bench observations.
>> However, I distrust nulling approaches like that for
>> reasons I've gone over many times on public forums
>> including probably this one.

> I'd be interested in hearing ... again

Paul Stamler's explanation does it right.

I can only add a practical example.

Let's say that a power amp's gain through the nulling circuit is 0.1 dB
different from ideal. It also has 1% THD. The output of the nulling device
is the same for either cause. Yet, a 0.1 dB level mismatch is always trivial
in the real world, while 1% THD can be a serious problem.

> ... why you think that.

Real world experience in many different contexts. Study of the relevant
technical literature as it was published over a period of 50 or more years.

> We assume a real speaker load on the power amp, in
> the same room (thus, microphonics are included in the
> test.)

The problem is not that nulling is insensitive. The problem is that nulling
conflates a wide variety of problems that have vastly different degrees of
audiblity.

[Scott Dorsey]

PStamler > wrote:
>
>I'm not going to get into the question of whether phase shifts at
>frequency extremes are audible. What I'm saying, rather, is that
>straight-wire null tests privilege phase shifts above all other errors
>to such a great extent that they are effectively useless.

I wouldn't say they are useless, I would just say that it's necessary
to actually analyze the difference component and see where it's coming
from before just concluding that there is a problem due to the mere
intensity average of the difference component.

They are still useful tests but they are not tests that can be used
without further analysis.

>In short, null tests are too sensitive to one parameter of dubious
>audibility, to the extent that other parameters are swamped.

This is true, but it's a thing that can be compensated for in many
cases.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Kevin Aylward[_4_]]

"William Sommerwerck" wrote in message
...

"Arny Krueger" >> wrote in message
...
>> "William Sommerwerck" >> wrote in
>> message

>>>>>> It is relatively straightforward to design an amplifier
>>>>>> that is a "straight piece of wire with gain".

>>>> Perhaps it is. What are your design criteria?

>> The usual answer is gain, input impedance, noise, nonlinear
>> distortion at all relevant frequencies, linear distortion, including
>> for power amps: Their performance into low impedance, nonlinear,
>> and reactive loads. On the AC supply side, power factor.

>We've argued this before, and those criteria are certainly pertinent. No
>one
>would design an amplifier without considering all of them. (Gerry Stanley
>famously said that the reason the DC-300A sounded better than the DC-300
>was
>that he hadn't paid attention to the earlier amplifier's behavior with
>reactive loads.)

>I ask the following, hoping you will carefully consider it before
>responding... How do you know that reducing harmonic and IM distortion to
>extremely low levels with test signals necessarily produces a comparable
>reduction in such distortions with program material?

Its called the laws of physics.

>In a broader sense, how
>do you know that an amplifier's behavior with a complex signal (ie, music)
>is accurately predicted by its behavior with simple signals?

Its called the laws of physics. There is nothing special about music
signals. Unfortunately, there are just too many unqualified individuals
around making all sorts of dubious claims that this is not so.

Sure, in principle one can consider some amps of 50 years ago, or tube amps
with ac coupling causing all sorts of dynamic biasing issues, or thermal
tail problems, but today, one would have to work pretty hard to get those
problems, well, not unless your design capabilities were somewhat less than
stellar.

If one takes a competentally designed DC coupled amplifier, and say, gets
0.01% IMD when driven with say, equal levels of steady state 19Khz and 20Khz
to just below clipping and at very small signals, its pretty much
inconceivable that the amp is not going to be a piece of wire with gain. In
principle, that one test is not measuring much, but in realty, it does.
Other aspects, all things being equal, go hand in hand.

The route of your question is, do the bias conditions of an amp change
significantly, when a signal is applied such that it makes the steady state
distortion tests invalid? Well, not if the amp is designed not to do that.

If an amplifier is linear, then a simple signal is all that is required to
predict the results for any signal. This is a provable mathematical fact. If
the amplifier is non-linear, than sure, more is required. However, if the
amplifier is "linear enough", than the simple tests are enough.



Kevin Aylward B.Sc.
www.kevinaylward.co.uk

[William Sommerwerck]

>> I ask the following, hoping you will carefully consider it before
>> responding... How do you know that reducing harmonic and IM
>> distortion to extremely low levels with test signals necessarily
>> produces a comparable reduction in such distortions with
>> program material?

> Its called the laws of physics.

<Mozart>
Oh? Which laws?
</Mozart>


>> In a broader sense, how do you know that an amplifier's behavior
>> with a complex signal (ie, music) is accurately predicted by its
>> behavior with simple signals?

> Its called the laws of physics. There is nothing special about music
> signals. Unfortunately, there are just too many unqualified individuals
> around making all sorts of dubious claims that this is not so.

Again, which laws? You can't cite the law of superposition (do you even know
what that is?), because it doesn't apply. Keep reading.


> If one takes a competentally designed DC coupled amplifier, and say,
> gets 0.01% IM when driven with say, equal levels of steady state 19Khz
> and 20Khz to just below clipping and at very small signals, its pretty
much
> inconceivable that the amp is not going to be a piece of wire with gain.

Not in my book. Keep reading.


> In principle, that one test is not measuring much, but in reality, it
does.
> Other aspects, all things being equal, go hand in hand.

Do you know what a tautology is? You talk about competently designed
amplifiers, but /that's/ the very thing we're trying to define! You haven't
told us what a competently defined amplifier IS! Simply having low measured
distortion with static signals DOES NOT demonstrate that an amplifier is
linear.


> The route [SIC!] of your question is, do the bias conditions of an amp
> change significantly, when a signal is applied such that it makes the
> steady state distortion tests invalid? Well, not if the amp is designed
> not to do that.

What does this have to do with the issue?


> If an amplifier is linear, then a simple signal is all that is required to
> predict the results for any signal.

Precisely. So how do you determine whether it's linear?

This is a perfect example of circular reasoning. If an amp has low measured
distortion, it has to be linear, and therefore behavies identically with
simple or complex signals. But its linearity with simple signals doesn't
prove its linearity with complex signals!

I urge you to find an intelligent teacher and have him explain the logic of
this to you.


> This is a provable mathematical fact. If the amplifier is non-linear, then
> sure, more is required. However, if the amplifier is "linear enough", than
> the simple tests are enough.

Prove it.

I invite anyone who believes that low meaured distortion equates
subjectively with low perceived distortion to find a Crown K-1 or K-2
amplifier and simply /listen/ to it. After you've recovered, measure it with
standard test signals, and tell us what there is in the measurements that
predicts why it sounds as awful as it does.

[Arny Krueger]

"William Sommerwerck" > wrote in
message

> Again, which laws? You can't cite the law of
> superposition (do you even know what that is?),

Gratiutious insult.

> because it doesn't apply. Keep reading.

Superposition is a highly exact model of real-world operation once a system
is sufficiently linear and stable.

In the case of audio, "sufficiently" is several times higher than the 0.01%
that Kevin used as his example.

Your problem Bill is that you have lived in the imaginary world of high end
audiophilia way too long. A few good DBTs would have straigtened you out a
few decades back, but you never did your homework.

[Kevin Aylward[_4_]]

"William Sommerwerck" wrote in message
...

>>>> I ask the following, hoping you will carefully consider it before
>>>> responding... How do you know that reducing harmonic and IM
>>>> distortion to extremely low levels with test signals necessarily
>>>> produces a comparable reduction in such distortions with
>>>> program material?

>> Its called the laws of physics.

<Mozart>>
Oh? Which laws?
</Mozart>>


>>>> In a broader sense, how do you know that an amplifier's behavior
>>>> with a complex signal (ie, music) is accurately predicted by its
>>>> behavior with simple signals?

>> Its called the laws of physics. There is nothing special about music
>> signals. Unfortunately, there are just too many unqualified individuals
>> around making all sorts of dubious claims that this is not so.

>Again, which laws? You can't cite the law of superposition (do you even
>know
>what that is?), because it doesn't apply. Keep reading.

Oh dear...

>> If one takes a competently designed DC coupled amplifier, and say,
>> gets 0.01% IM when driven with say, equal levels of steady state 19Khz
>> and 20Khz to just below clipping and at very small signals, its pretty
much
>> inconceivable that the amp is not going to be a piece of wire with gain.

>Not in my book.

I would suggest that you are reading the wrong books.

> Keep reading.

Why?

>> In principle, that one test is not measuring much, but in reality, it
does.
>> Other aspects, all things being equal, go hand in hand.

>Do you know what a tautology is?

My favourite tautology is one of my own.

http://www.kevinaylward.co.uk/replicators/index.html

"That which is mostly observed, is that which replicates the most."

Its amazingly useful. For instance, it tells us that, statistically, men
will have sex at every reasonable opportunity and women won't.

>You talk about competently designed
>amplifiers, but /that's/ the very thing we're trying to define! You haven't
>told us what a competently defined amplifier IS! Simply having low measured
>distortion with static signals DOES NOT demonstrate that an amplifier is
>linear.

By and large, it does.

Subject to a few reasonable mathematical conditions, we can express any
amplifier by a Taylor power series for its output voltage with respect to
input voltage. Actually, to be more exact, we actually need a Volterre
series, but the net effect is still a power series expansion.

The point being that if the system is nonlinear at all, it is provable
that there must be harmonic and intermodulation distortion. Conversely, if
the distortion for steady state signals is sufficiently low, then the system
must be linear, subject to conditions I already mentioned.

For the Taylor approach, we have:

Vout = sum An.Vin^n

If Vin = Vpk.Sin(wt), then the power terms generate a series harmonic
frequencies, via relations such as sin^2(x) = (1-cos(x)/2. If the system is
linear, then no harmonic frequencies are
generated.

>> The route [SIC!] of your question is, do the bias conditions of an amp
>> change significantly, when a signal is applied such that it makes the
>> steady state distortion tests invalid? Well, not if the amp is designed
>> not to do that.

>What does this have to do with the issue?

A lot.

For example, in principle, one could construct an amplifier that used its
own output to charge up a supply capacitor, that was used as a supply for
itself. In a steady state test the amplifier might be biased up correctly
with the right voltages and currents from that supply. However, it may be
that it takes 100 cycles for that that supply capacitor to charge up, hence
transient busts of sine pulses, might well show distorted sine bursts.

So, to solve that sort of problem, don't do it.

>> If an amplifier is linear, then a simple signal is all that is required
>> to
>> predict the results for any signal.

>Precisely. So how do you determine whether it's linear?

er... feed in a sine wave and see if other frequencies get generated.

>This is a perfect example of circular reasoning. If an amp has low measured
>distortion, it has to be linear, and therefore behavies identically with
>simple or complex signals. But its linearity with simple signals doesn't
>prove its linearity with complex signals!

See above, by and large it does. Linearity is independent of the waveform,
by definition. Except for the type of situation I described above, which can
be eliminated by correct design, if there are no harmonics, then the system
is linear.

>I urge you to find an intelligent teacher and have him explain the logic of
>this to you.

Ahmmm...I think you might do well to take a course on Signal Processing.

>> This is a provable mathematical fact. If the amplifier is non-linear,
>> then
>> sure, more is required. However, if the amplifier is "linear enough",
>> than
>> the simple tests are enough.

>Prove it.

>I invite anyone who believes that low measured distortion equates
>subjectively with low perceived distortion

It is a known fact that adding small amounts of distortion, can actuality
make things sound "cleaner". So, there is some truth in what you say here.


>to find a Crown K-1 or K-2
>amplifier and simply /listen/ to it. After you've recovered, measure it
>with
>standard test signals, and tell us what there is in the measurements that
>predicts why it sounds as awful as it does.

One needs to do distortion tests at various amplitudes. It is certainly
possible to quote misleading figures. One needs to account for 1mW and 100W
levels. If at all levels, its at the 0.01% IMD at 20khz/19khz, its a
straight piece of wire with gain.



Regards

Kevin Aylward B.Sc.
www.kevinaylward.co.uk

[Scott Dorsey]

Kevin Aylward > wrote:
>The point being that if the system is nonlinear at all, it is provable
>that there must be harmonic and intermodulation distortion. Conversely, if
>the distortion for steady state signals is sufficiently low, then the system
>must be linear, subject to conditions I already mentioned.

Right, but how low is low?

Hint: the THD number is no longer useful. Back in the days when amplifiers
were all similar topologies and distortion spectra were similar, it was very
useful for comparing amplifiers. This is no longer the case.

>For the Taylor approach, we have:
>
>Vout = sum An.Vin^n
>
>If Vin = Vpk.Sin(wt), then the power terms generate a series harmonic
>frequencies, via relations such as sin^2(x) = (1-cos(x)/2. If the system is
>linear, then no harmonic frequencies are
>generated.

Right. But generation of harmonics depends on the nonlinearities involved.

I can build you a box with 2% distortion that you will have a hard time
identifying as being in-circuit or out of circuit. I can built you another
box with 0.01% distortion which is painfully obvious. The first box is
mostly third harmonic, the next box is mostly sixth.

But note ALSO, and this is the most important part, that the subtraction
test does not detect only harmonics. If there is any group delay in the
channel, or any small frequency response changes, products will appear in
the differential product. These are the result of distortions which are
not terribly audible, maybe not audible at all in the case of the group
delay, but which become very prominant in the subtraction test.

The subtraction test is a useful tool but only when the differential
product is analyzed. Just listening to it and measuring the amplitude
is not sufficient and is apt to be misleading.

Likewise the THD measure is not useful for comparing systems of different
distortion spectra. Folks are working on weighted measures like the
Geddes-Lee test for that but we're not there yet.

>>I invite anyone who believes that low measured distortion equates
>>subjectively with low perceived distortion
>
>It is a known fact that adding small amounts of distortion, can actuality
>make things sound "cleaner". So, there is some truth in what you say here.

Mostly that's high order even stuff, and it's the principle by which
the Aural Exciter and the BBE boxes operate. It's also a lot of why
there were problems with much of the early-seventies solid state amps
that resulted in an odd split of listeners' opinions.

>One needs to do distortion tests at various amplitudes. It is certainly
>possible to quote misleading figures. One needs to account for 1mW and 100W
>levels. If at all levels, its at the 0.01% IMD at 20khz/19khz, its a
>straight piece of wire with gain.

Maybe, but at which point does that happen?
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Anahata]

On Sun, 30 Jan 2011 10:26:54 -0500, Scott Dorsey wrote:

> The subtraction test is a useful tool but only when the differential
> product is analyzed. Just listening to it and measuring the amplitude
> is not sufficient and is apt to be misleading.

I seem to remember first encountering the subtraction test in an article
in Wireless Word (if it still called that then) in the 1960s by Peter
Baxandall. In the application where he used it, on an audio power
amplifier, the difference signal, with only some simple passive HF phase/
delay compensation to get a null, amplified with the same gain as the
amplifier under test, was inaudible.

I agree that audible results from a subtraction test need to be carefully
analysed, but if the result is silence, it surely tells us the amplifier
is good enough for all practical purposes.

There was some audiophile reaction that suggested that a distortion
component too low to be inaudible by itself could still somehow audibly
affect the sound when mixed to the signal, but all the work on auditory
masking doesn't tend to support this theory.

--
Anahata
-+- http://www.treewind.co.uk
Home: 01638 720444 Mob: 07976 263827

[Scott Dorsey]

Anahata > wrote:
>I seem to remember first encountering the subtraction test in an article
>in Wireless Word (if it still called that then) in the 1960s by Peter
>Baxandall. In the application where he used it, on an audio power
>amplifier, the difference signal, with only some simple passive HF phase/
>delay compensation to get a null, amplified with the same gain as the
>amplifier under test, was inaudible.

Right... but then comes the question of how much gain can you add to make
it audible.

>I agree that audible results from a subtraction test need to be carefully
>analysed, but if the result is silence, it surely tells us the amplifier
>is good enough for all practical purposes.

I'll buy that. You have to have an actual speaker load on the thing, though.
not just a pure resistance.

>There was some audiophile reaction that suggested that a distortion
>component too low to be inaudible by itself could still somehow audibly
>affect the sound when mixed to the signal, but all the work on auditory
>masking doesn't tend to support this theory.

I don't buy that. But I do buy the theory that someone else may have a
lower threshold of hearing than I have.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Kevin Aylward[_4_]]

"Scott Dorsey" wrote in message ...

Kevin Aylward >> wrote:
>>The point being that if the system is nonlinear at all, it is provable
>>that there must be harmonic and intermodulation distortion. Conversely, if
>>the distortion for steady state signals is sufficiently low, then the
>>system
>>must be linear, subject to conditions I already mentioned.

>Right, but how low is low?

>Hint: the THD number is no longer useful.

I don't agree. THD is very, very useful. It is one of the most useful
measures of the linearity of an amplifier. However, one needs to apply it
correctly. I actually prefer IMD, because IMD identifies components not
harmonically related to either input signal, hence, more detectable.

>Back in the days when amplifiers
>were all similar topologies and distortion spectra were similar, it was
>very
>useful for comparing amplifiers. This is no longer the case.

I don't agree, and don't see any support for this claim.

I am not really discussing comparing amplifiers on a 1% verses 0.5%,
especially, at single operating levels. Its trivial that one can have a
single measurement at 0.1% and have it sounding much worse that an amp with
1%. I am referring to the design of a straight piece of wire with gain,
where attention has been made for distortion at all operating levels.

For example, one can do a single measurement at say, full power and obtain
low distortion, yet have gross x-over distortion, such that the amplifier
sounds dreadful on real music peaking at full power. However, this is a
cheat. When, I stated all IMD products I mean, all IMD at any operating
level. Lower levels distortion for such an amp can be huge, which is where a
music signal spends most of its time.

>>For the Taylor approach, we have:
>>
>>Vout = sum An.Vin^n
>>
>>If Vin = Vpk.Sin(wt), then the power terms generate a series harmonic
>>frequencies, via relations such as sin^2(x) = (1-cos(x)/2. If the system
>>is
>>linear, then no harmonic frequencies are
>>generated.

>Right. But generation of harmonics depends on the nonlinearities involved.

Sure, its inherent in the Taylor expansion that the specific value of the
co-efficient result in different spectrums of harmonics.

>I can build you a box with 2% distortion that you will have a hard time
>identifying as being in-circuit or out of circuit. I can built you another
>box with 0.01% distortion which is painfully obvious. The first box is
>mostly third harmonic, the next box is mostly sixth.

Sure, it is possible to deliberately construct pathological/poor amplifiers
that have strange characteristics to prove a point for the purposes of
oneupmanship debate, but I am discussing real amplifiers, that are
competently designed. I could certainly construct an amplifier with a very
low on off spot level distortion, yet sound bad on audio tests.

As I already claimed, if an amplifier has < 0.01% IMD, at all operating
levels, I don't accept that one can distinguish that amplifier from a
straight piece of wire. You would have to cite some evidence of actual tests
to support your view here. All evidence I am aware of, contradicts your
claim for general amplifiers so designed.


>Likewise the THD measure is not useful for comparing systems of different
>distortion spectra. Folks are working on weighted measures like the
>Geddes-Lee test for that but we're not there yet.

I think you miss my point. Sure 0.5% second sounds way different that 0.5%
third. This is all well understood, and has been understood for many years.
My claim is not about the differences of larger level distortions, but a
claim that if the thd/imd distortion is *sufficiently* low, at *all*
operating levels, than the amplifier is a straight piece of wire with gain.

>>One needs to do distortion tests at various amplitudes. It is certainly
>>possible to quote misleading figures. One needs to account for 1mW and
>>100W
>>levels. If at all levels, its at the 0.01% IMD at 20khz/19khz, its a
>>straight piece of wire with gain.

Maybe, but at which point does that happen?

I cant say exactly, but the above figure is used because, it pretty much
impossible to design an amplifier that has pathological characteristics that
would generate say, larger distortion at lower frequencies, and a figure
that would minimise disagreements. I personally believe the figure is much
higher. Full power IMD at 19kh/20khz is a very severe test.

An amplifier specifically designed to be a straight piece of wire should
have massive amounts of feedback, such that lower frequencies, distortion is
effectively non existent. For example, my Studiomaster MOSFET 1000 design
had < 0.005% THD at 20khz at 300W/8 ohm. Sure, at 500W/4ohm it went up to
0.03%, but at that frequency, a 4 ohm speaker load is way more than 4 ohms.
I don't actually know the distortion at 1khz because the output measured
0.0015% THD with the input measuring 0.0018% THD!

So, a pint of Guinness for the explanation for this apparent distortion
reduction characteristic.

The point, is that all things being equal, when one designs a decent DC
coupled power amp, things all go hand in hand. This is not true for say, the
design of tube guitar amps.


Regards

Kevin Aylward B.Sc.

www.kevinaylward.co.uk

[Scott Dorsey]

Kevin Aylward > wrote:
>"Scott Dorsey" wrote in message ...
>
>>Right. But generation of harmonics depends on the nonlinearities involved.
>
>Sure, its inherent in the Taylor expansion that the specific value of the
>co-efficient result in different spectrums of harmonics.
>
>>I can build you a box with 2% distortion that you will have a hard time
>>identifying as being in-circuit or out of circuit. I can built you another
>>box with 0.01% distortion which is painfully obvious. The first box is
>>mostly third harmonic, the next box is mostly sixth.
>
>Sure, it is possible to deliberately construct pathological/poor amplifiers
>that have strange characteristics to prove a point for the purposes of
>oneupmanship debate, but I am discussing real amplifiers, that are
>competently designed. I could certainly construct an amplifier with a very
>low on off spot level distortion, yet sound bad on audio tests.

Real amplifiers like... say... a Dynaco ST120. Okay, maybe that's not
competently designed but it was typical of the design in the era and it
has a whole lot of high order even harmonic trash coming out of it.

>As I already claimed, if an amplifier has < 0.01% IMD, at all operating
>levels, I don't accept that one can distinguish that amplifier from a
>straight piece of wire. You would have to cite some evidence of actual tests
>to support your view here. All evidence I am aware of, contradicts your
>claim for general amplifiers so designed.

It's possible. I can provide a cite, though, showing amps with < 0.01% THD
in bench tests that show audible distortion. Of course, there are plenty
with that level (and a lot with much higher levels) that are not.

>>Likewise the THD measure is not useful for comparing systems of different
>>distortion spectra. Folks are working on weighted measures like the
>>Geddes-Lee test for that but we're not there yet.
>
>I think you miss my point. Sure 0.5% second sounds way different that 0.5%
>third. This is all well understood, and has been understood for many years.
>My claim is not about the differences of larger level distortions, but a
>claim that if the thd/imd distortion is *sufficiently* low, at *all*
>operating levels, than the amplifier is a straight piece of wire with gain.

Right. But at what point is it "sufficiently low?" 0.1%? 0.01%? 0.001?

Remember, 0.01% THD means the total sum of harmonics is 40 dB down. That's
pretty far down. But if it's all concentrated in one harmonic product,
it's going to be audible at 40 dB down.

>I cant say exactly, but the above figure is used because, it pretty much
>impossible to design an amplifier that has pathological characteristics that
>would generate say, larger distortion at lower frequencies, and a figure
>that would minimise disagreements. I personally believe the figure is much
>higher. Full power IMD at 19kh/20khz is a very severe test.

The larger distortion at lower frequencies thing is actually very common
and a result of using undersized electrolytic coupling caps. Doug Self
actually has a nice discussion of this in his amp design handbook. Turns
out that the capacitor values required for low distortion at low frequencies
are a lot higher than the values required for flat response.

My experience is that it can also be a sign of pollution on power supply
rails due to insufficient decoupling.

>An amplifier specifically designed to be a straight piece of wire should
>have massive amounts of feedback, such that lower frequencies, distortion is
>effectively non existent. For example, my Studiomaster MOSFET 1000 design
>had < 0.005% THD at 20khz at 300W/8 ohm. Sure, at 500W/4ohm it went up to
>0.03%, but at that frequency, a 4 ohm speaker load is way more than 4 ohms.
>I don't actually know the distortion at 1khz because the output measured
>0.0015% THD with the input measuring 0.0018% THD!

Massive amounts of feedback can be a good thing when the poles and zeroes
are in the right place, but it can also be trouble when driving bizarre
speaker loads, and a lot of speaker loads are bizarre. But yes, I agree
that feedback is a wonderful thing. I also agree that the system needs to
be linear in the first place before you add feedback.

>So, a pint of Guinness for the explanation for this apparent distortion
>reduction characteristic.

Bandlimiting, I would guess first off.

>The point, is that all things being equal, when one designs a decent DC
>coupled power amp, things all go hand in hand. This is not true for say, the
>design of tube guitar amps.

Oh, this is absolutely true.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[PStamler]

On Feb 1, 9:17*am, "Kevin Aylward" >
wrote:
> I don't actually know the distortion at 1khz because the output measured
> 0.0015% THD with the input measuring 0.0018% THD!
>
> So, a pint of Guinness for the explanation for this apparent distortion
> reduction characteristic.

Perhaps the amplifier generates harmonics in opposite poarity to those
in the signal generator, and they partially cancel?

Peace,
Paul

[PStamler]

Another limitation of continuous distortion tests -- of any sort -- is
that they don't measure certain forms of misbehavior that amplifiers
exhibit when driving speakers. A good example is what happens when
loudspeakers are fed a succession of low-frequency impulses in rapid
succession; the speaker can react in a way that draws excessive
current from an amplifier. A nominal 6-ohm speaker can act more like 2
ohms. Couple that with an amplifier that has a saggy power supply
after several impulses, and you can get real problems that *don't*
show up on continuous-signal tests. And to those who call this an
artificial torture test, not likely to happen in the real world, I
point to kickdrums.

Bob Cordell has a discussion of this in his excellent new book on
solid-state power amplifier design. He identifies other problems not
caught by the standard THD and IMD tests.

I'm not defending mysticism here, just saying that one particular set
of tests won't completely characterize the performance of an audio
device.

Peace,
Paul

[Kevin Aylward[_4_]]

"Scott Dorsey" wrote in message ...

Kevin Aylward >> wrote:
>>"Scott Dorsey" wrote in message ...
>>
>>>>Right. But generation of harmonics depends on the nonlinearities
>>>>involved.
>>
>>Sure, its inherent in the Taylor expansion that the specific value of the
>>co-efficient result in different spectrums of harmonics.
>>
>>>>I can build you a box with 2% distortion that you will have a hard time
>>>>identifying as being in-circuit or out of circuit. I can built you
>>>>another
>>>>box with 0.01% distortion which is painfully obvious. The first box is
>>>>mostly third harmonic, the next box is mostly sixth.
>>
>>Sure, it is possible to deliberately construct pathological/poor
>>amplifiers
>>that have strange characteristics to prove a point for the purposes of
>>oneupmanship debate, but I am discussing real amplifiers, that are
>>competently designed. I could certainly construct an amplifier with a very
>>low on off spot level distortion, yet sound bad on audio tests.

>Real amplifiers like... say... a Dynaco ST120. Okay, maybe that's not
>competently designed but it was typical of the design in the era and it
>has a whole lot of high order even harmonic trash coming out of it.

I don't know about this amp. It might have slewing problems. So many earlier
amps just did not have full power high frequency response, which could be an
issue on some types of audio signals.


>>>>Likewise the THD measure is not useful for comparing systems of
>>>>different
>>>>distortion spectra. Folks are working on weighted measures like the
>>>>Geddes-Lee test for that but we're not there yet.
>>
>>I think you miss my point. Sure 0.5% second sounds way different that 0.5%
>>third. This is all well understood, and has been understood for many
>>years.
>>My claim is not about the differences of larger level distortions, but a
>>claim that if the thd/imd distortion is *sufficiently* low, at *all*
>>operating levels, than the amplifier is a straight piece of wire with
>>gain.

>Right. But at what point is it "sufficiently low?" 0.1%? 0.01%? 0.001?

Somewhere above 0.01% in my view. One has to note that speakers also have a
lot a distortion.


>The larger distortion at lower frequencies thing is actually very common
>and a result of using undersized electrolytic coupling caps. Doug Self
>actually has a nice discussion of this in his amp design handbook. Turns
>out that the capacitor values required for low distortion at low
>frequencies
>are a lot higher than the values required for flat response.

I am quite aware of Douglas Self. He is very knowledgeable. Well, "low
distortion" here is a bit undefined. Typically, its going to be < 0.001%
over typical ranges of voltages on "small signal" coupling capacitors. So in
general, coupling capacitors is not a real problem. Douglas does present
some data (http://www.douglas-self.com/ampins/dipa/dipa.htm#2) on a speaker
output coupling capacitors, showing a midband rise to 0.003%, which is a
significant increases on his "blameless amplifier", but this is still so
low, that is not audibly significant in my view. I used a 5Hz LF point for
my Mosfet 1000 amp to avoid this potential issue though.

Actually, Douglas is a bit of a conundrum for me. He clearly know a lot, but
his "blameless amp" is not the "best/optimum" architecture in my view, if
"best/optimum" can actually be defined. His second stage is not
differential, and uses a fixed constant current load. A differential,
current mirror loaded second stage gives inherent lower distortion for that
second stage, and gives a somewhat "better" push pull drive to the next
stage. A fixed current load mean that the gain transistor is always tugging
at that current source.


>My experience is that it can also be a sign of pollution on power supply
>rails due to insufficient decoupling.

>>An amplifier specifically designed to be a straight piece of wire should
>>have massive amounts of feedback, such that lower frequencies, distortion
>>is
>>effectively non existent. For example, my Studiomaster MOSFET 1000 design
>>had < 0.005% THD at 20khz at 300W/8 ohm. Sure, at 500W/4ohm it went up to
>>0.03%, but at that frequency, a 4 ohm speaker load is way more than 4
>>ohms.
>>I don't actually know the distortion at 1khz because the output measured
>>0.0015% THD with the input measuring 0.0018% THD!

>Massive amounts of feedback can be a good thing when the poles and zeroes
>are in the right place, but it can also be trouble when driving bizarre
>speaker loads, and a lot of speaker loads are bizarre.

One has to be careful in the design of the loop, but using the right output
network to disconnect the load at HF, usually works ok for pretty much any
load. I could certainly run my Mosfet 1000 into a 2uf capacitor. In fact, I
was quite chuffed that I managed with only a 22nf/10ohm output damper. Many
amps use a 0.1uf. Testing at 200Khz full power is more problematic when
driving a 0.1uf

> But yes, I agree
>that feedback is a wonderful thing. I also agree that the system needs to
>be linear in the first place before you add feedback.

Yes and no. I agree that feedback won't help for slew rate limiting,
essentially, because the gain tends to zero. If there aint enough current,
then there is not enough current. It can help sometimes to have lower open
loop distortion, but I have done quite a few actual measurements on this,
and as far as the numbers go, having more local feedback, usually results in
more total distortion.

For example, suppose one puts in emitter resisters in the input pair. This
linearises the input pair a fair bit, but because, all things being equal,
it also reduces the overall loop gain, resulting in larger distortion of the
whole amplifier. The input pair does not usually dominate the distortion of
a power amp. In the bigger picture, having some emitter degradation can
effectively reduce distortion at HF, in the sense that it can allow the
amplifier to be designed to have a higher slew rate by reducing the loop
gain.


>>So, a pint of Guinness for the explanation for this apparent distortion
>>reduction characteristic.

>Bandlimiting, I would guess first off.

THD equipment measurers "distortion and noise". The oscillator signal was
around 1V, the amp output was around 50V...

So, I estimate that the amp was dong <0.001%

>>The point, is that all things being equal, when one designs a decent DC
>>coupled power amp, things all go hand in hand. This is not true for say,
>>the
>>design of tube guitar amps.

>Oh, this is absolutely true.

One common fallacy is that tube guitar amps (essentially class B) when
overloaded generate even distortion. One only has to apply a signal and look
on a scope to see that this is nonsense. One actually sees huge x-over
distortion. Grids start taking current and nasty things start happening.

Regards

Kevin Aylward B.Sc.

www.kevinaylward.co.uk

[Scott Dorsey]

Kevin Aylward > wrote:
>"Scott Dorsey" wrote in message ...
>
>>Real amplifiers like... say... a Dynaco ST120. Okay, maybe that's not
>>competently designed but it was typical of the design in the era and it
>>has a whole lot of high order even harmonic trash coming out of it.
>
>I don't know about this amp. It might have slewing problems. So many earlier
>amps just did not have full power high frequency response, which could be an
>issue on some types of audio signals.

It has severe slewing problems. Also a lot of other interesting issues...
the power supply is undersized so noise from the output stage on the rails
winds up in the input stage... and that noise is mostly even harmonics.
The 1 KHz THD numbers are great and the supply stays more or less steady,
but put something with high and low frequencies into it at the same time
and the supply rails look like the Swiss Alps on a scope.

It's also a unipolar supply with all the issues that brings up.

>>>My claim is not about the differences of larger level distortions, but a
>>>claim that if the thd/imd distortion is *sufficiently* low, at *all*
>>>operating levels, than the amplifier is a straight piece of wire with
>>>gain.
>
>>Right. But at what point is it "sufficiently low?" 0.1%? 0.01%? 0.001?
>
>Somewhere above 0.01% in my view. One has to note that speakers also have a
>lot a distortion.

Yes, and the speaker distortion in almost every case is going to swamp the
amplifier distortion. Still, you admit that the difference between .1% and
..01% distortion is audible... and the problem is that it's audible on
speakers that might be rated for as much as 5% distortion. That's because
the distortion spectra of the speakers and the amplifiers are different.

>I am quite aware of Douglas Self. He is very knowledgeable. Well, "low
>distortion" here is a bit undefined. Typically, its going to be < 0.001%
>over typical ranges of voltages on "small signal" coupling capacitors. So in
>general, coupling capacitors is not a real problem. Douglas does present
>some data (http://www.douglas-self.com/ampins/dipa/dipa.htm#2) on a speaker
>output coupling capacitors, showing a midband rise to 0.003%, which is a
>significant increases on his "blameless amplifier", but this is still so
>low, that is not audibly significant in my view. I used a 5Hz LF point for
>my Mosfet 1000 amp to avoid this potential issue though.

The problem is that it builds up. You get .001% distortion from a coupling
cap, then you put a couple hundred of them in the signal path and the end
result is a lot of distortion. Not a huge issue for a small power amp but
a big one for a mixing console.

But... let's take a degenerate case to show why a single scalar is
not useful. Pick a Phase Linear 700 for instance.... non-complementary
output stage built with TV horizontal output transistors not known for
their linearity. Lots of crossover distortion because the bottom part
of the curve is so ragged. Lots and lots of feedback which helps linearize
the amp to a great extent.

Full power THD on the amp is a really nice low number, something in the .001%
range as I recall. However, when you run the amp down to the one or two watt
level, the dead band resulting from the crossover issues becomes a much
larger portion of your signal and the total distortion percentage goes through
the roof.

Yeah, you could model the whole system as a Volterra series and publish it
on the datasheet if you wanted to, but that probably wouldn't help potential
purchasers any more than the single scalar does.

>actually, Douglas is a bit of a conundrum for me. He clearly know a lot, but
>his "blameless amp" is not the "best/optimum" architecture in my view, if
>"best/optimum" can actually be defined. His second stage is not
>differential, and uses a fixed constant current load. A differential,
>current mirror loaded second stage gives inherent lower distortion for that
>second stage, and gives a somewhat "better" push pull drive to the next
>stage. A fixed current load mean that the gain transistor is always tugging
>at that current source.

He actually talks about the advantages and disadvantages of making the
second stage differential in tha latest edition of his book. He claims it
doesn't actually buy a reduction in distortion in the long run. He is an
odd character and he is set in his ways in a lot of cases, but although he
sometimes has bizarre opinions he always has good numbers to back them up.

>>Massive amounts of feedback can be a good thing when the poles and zeroes
>>are in the right place, but it can also be trouble when driving bizarre
>>speaker loads, and a lot of speaker loads are bizarre.
>
>One has to be careful in the design of the loop, but using the right output
>network to disconnect the load at HF, usually works ok for pretty much any
>load. I could certainly run my Mosfet 1000 into a 2uf capacitor. In fact, I
>was quite chuffed that I managed with only a 22nf/10ohm output damper. Many
>amps use a 0.1uf. Testing at 200Khz full power is more problematic when
>driving a 0.1uf

A 2 uF capacitor is.... about like a stacked pair of original Quad ESLs....
granted that's a pretty crazy load but to my mind you can never have enough
margins....

>Yes and no. I agree that feedback won't help for slew rate limiting,
>essentially, because the gain tends to zero. If there aint enough current,
>then there is not enough current. It can help sometimes to have lower open
>loop distortion, but I have done quite a few actual measurements on this,
>and as far as the numbers go, having more local feedback, usually results in
>more total distortion.
>
>For example, suppose one puts in emitter resisters in the input pair. This
>linearises the input pair a fair bit, but because, all things being equal,
>it also reduces the overall loop gain, resulting in larger distortion of the
>whole amplifier. The input pair does not usually dominate the distortion of
>a power amp. In the bigger picture, having some emitter degradation can
>effectively reduce distortion at HF, in the sense that it can allow the
>amplifier to be designed to have a higher slew rate by reducing the loop
>gain.

Yes. It is a constant juggling act. That is what makes it interesting.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Kevin Aylward[_4_]]

"PStamler" wrote in message
...

>Another limitation of continuous distortion tests -- of any sort -- is
>that they don't measure certain forms of misbehavior that amplifiers
>exhibit when driving speakers. A good example is what happens when
>loudspeakers are fed a succession of low-frequency impulses in rapid
>succession; the speaker can react in a way that draws excessive
>current from an amplifier. A nominal 6-ohm speaker can act more like 2
>ohms.

I think this is probably a bit excessive at a 3:1 ratio, but sure, one can
generate pulse waveforms into a simple model of a speaker and show larger
peak spike currents than that indicated Vpk/RDC with certain waveforms, e.g.
see http://www.epanorama.net/documents/audio/speaker_impedance.html for the
model. A simple model, for square wave inputs would give short pulse spikes
of twice Vpk/Rdc, i.e. a simple HP filter on RDC and Cmes type effect.

This can still be evaluated from simple steady state, e.g. bursts of sine
and square waves.

> Couple that with an amplifier that has a saggy power supply
>after several impulses, and you can get real problems that *don't*
>show up on continuous-signal tests. And to those who call this an
>artificial torture test, not likely to happen in the real world, I
>point to kickdrums.

I think this may miss a basic point. By construction, one needs to operate
the amplifier within its non overload region. By construction, an amplifier
needs to be designed such that it can reach its rated power into a rated
impedance e.g. 4 ohms or 8 ohms. By construction, speakers rated at say, 4
ohm should have a minimum resistance of 4 ohms. Typically they may be a bit
larger, e.g. 4.5. However, a decent amp always has a certain amount of
transient overload current available. My mosfet 1000 could do about twice
rated current continuously, until the thermal came in. So, one can indeed
use steady state tests, they just need to be done into about 1/2 the rated
load resistance!

Actually, the kick drum is not a great example for your point. To achieve
the above twice nominal continuous peak currents requires continuous fast
edges for the main waveform. The basic frequencies of drums are relatively
low so this effect is not so severe.

A saggy power supply is actually better. If measurements have been made in
steady state, the power supply will be at its lowest point, such that an
amplifier rated at for steady state conditions, will be able to more volts
for short busts.

>Bob Cordell has a discussion of this in his excellent new book on
>solid-state power amplifier design. He identifies other problems not
>caught by the standard THD and IMD tests.

The point I am making is that, if one competently designs an amplifier with
very low THD/IMD, despite the fact that, in principle there may be other
issues, they are all part an parcel of achieving such an amp.

>I'm not defending mysticism here, just saying that one particular set
>of tests won't completely characterize the performance of an audio
>device.

In principle possibly, but in practice, THD/IMD over all operating
frequencies and output levels (including overload), and some burst tests
will, if one is designing a straight piece of wire with gain, should be
enough. Achieving such 0.01% levels has actually been achievable with
trivial designs for at least 30 years.

Regards

Kevin Aylward B.Sc.

www.kevinaylward.co.uk

[Anahata]

On Wed, 02 Feb 2011 15:17:27 +0000, Kevin Aylward wrote:
>
> an amplifier needs to be designed such that it can reach its rated power
> into a rated impedance e.g. 4 ohms or 8 ohms.

With some amplifiers that only works for a pure resistive load.

> By construction, speakers
> rated at say, 4 ohm should have a minimum resistance of 4 ohms.
> Typically they may be a bit larger, e.g. 4.5.

In practice, the crossover/speaker combination often goes below the
nominal impedance of the speaker. For a start, the DC resistance is
usually less, but the RC network may present a low impedances at one
frequency.

> However, a decent amp
> always has a certain amount of transient overload current available. My
> mosfet 1000 could do about twice rated current continuously, until the
> thermal came in.

That's good conservative design, but not always found in commercially
available amplifiers. I've seen (and heard!) a supposedly professional
grade power amplifier go into foldback limiting with a speaker whose
impedance was very reactive at some frequencies.

This is all beside the point though, as I think Paul was suggesting
audible LF artifacts appearing at the output as a result, perhaps, of
power supply or bias chain modulation, not failure of the amplifier to
deliver the required current. If a repeated mid/HF toneburst causes
thumping noises in the speakers, that's a kind of distortion, but it's
not necessarily caused by current limiting, and nor can it be revealed by
steady state tone tests.

--
Anahata
--/-- http://www.treewind.co.uk
+44 (0)1638 720444

[Kevin Aylward[_4_]]

"Scott Dorsey" wrote in message ...

Kevin Aylward >> wrote:
>>"Scott Dorsey" wrote in message ...
>>
>>>>Real amplifiers like... say... a Dynaco ST120. Okay, maybe that's not
>>>>competently designed but it was typical of the design in the era and it
>>>>has a whole lot of high order even harmonic trash coming out of it.
>>
>>I don't know about this amp. It might have slewing problems. So many
>>earlier
>>amps just did not have full power high frequency response, which could be
>>an
>>issue on some types of audio signals.

>It has severe slewing problems. Also a lot of other interesting issues...
>the power supply is undersized so noise from the output stage on the rails
>winds up in the input stage... and that noise is mostly even harmonics.
>The 1 KHz THD numbers are great and the supply stays more or less steady,
>but put something with high and low frequencies into it at the same time
>and the supply rails look like the Swiss Alps on a scope.

>It's also a unipolar supply with all the issues that brings up.

>>>>>>My claim is not about the differences of larger level distortions, but
>>>>>>a
>>>>>>claim that if the thd/imd distortion is *sufficiently* low, at *all*
>>>>>>operating levels, than the amplifier is a straight piece of wire with
>>>>>>gain.
>>
>>>>Right. But at what point is it "sufficiently low?" 0.1%? 0.01%?
>>>>0.001?
>>
>>Somewhere above 0.01% in my view. One has to note that speakers also have
>>a
>>lot a distortion.

>Yes, and the speaker distortion in almost every case is going to swamp the
>amplifier distortion. Still, you admit that the difference between .1% and
>.01% distortion is audible...

Actually, I claim that below 0.01%, at all power levels, it is not
detectable. I don't really make a clear claim for figures above that, but I
am of the opinion that if IMD at *all* reasonable power levels and
frequencies is below 0.05%, it is also not detectable. I other words,
someone would have to give me proof that they could detect such distortions.

>and the problem is that it's audible on
>speakers that might be rated for as much as 5% distortion. That's because
>the distortion spectra of the speakers and the amplifiers are different.

>>I am quite aware of Douglas Self. He is very knowledgeable. Well, "low
>>distortion" here is a bit undefined. Typically, its going to be < 0.001%
>>over typical ranges of voltages on "small signal" coupling capacitors. So
>>in
>>general, coupling capacitors is not a real problem. Douglas does present
>>some data (http://www.douglas-self.com/ampins/dipa/dipa.htm#2) on a
>>speaker
>>output coupling capacitors, showing a midband rise to 0.003%, which is a
>>significant increases on his "blameless amplifier", but this is still so
>>low, that is not audibly significant in my view. I used a 5Hz LF point for
>>my Mosfet 1000 amp to avoid this potential issue though.

>The problem is that it builds up. You get .001% distortion from a coupling
>cap, then you put a couple hundred of them in the signal path and the end
>result is a lot of distortion. Not a huge issue for a small power amp but
>a big one for a mixing console.

Well, 100 in in the path is a probably bit of an over estimate, no one
really wants to spend that sort of build cost, but sure, no one sets the
turnover at 20Hz if the whole system is to be specked at 20Hz - 20Khz +/-1db
anyway.

>But... let's take a degenerate case to show why a single scalar is
>not useful. Pick a Phase Linear 700 for instance.... non-complementary
>output stage built with TV horizontal output transistors not known for
>their linearity. Lots of crossover distortion because the bottom part
>of the curve is so ragged. Lots and lots of feedback which helps linearize
>the amp to a great extent.
>Full power THD on the amp is a really nice low number, something in the
>.001%
>range as I recall. However, when you run the amp down to the one or two
>watt
>level, the dead band resulting from the crossover issues becomes a much
>larger portion of your signal and the total distortion percentage goes
>through
>the roof.
>Yeah, you could model the whole system as a Volterra series and publish it
>on the datasheet if you wanted to, but that probably wouldn't help
>potential
>purchasers any more than the single scalar does.

And that's my point. I don't suggest a single point at full output. One
needs at least two points to include a value that reflects x-over
distortion. One also needs to know that the amp does not have some
pathological behaviour that makes an implication of performance not actually
specified, false.

I don't think anyone really cares today about the numbers for the area I am
interested in. i.e. P.A amplifiers for live band work. Many manufactures
don't quote any/many numbers nowadays. 30 years ago, it was more of a
numbers game. Today, most commercial PA amplifiers are worse than that was
achieved 30 years ago.

>>actually, Douglas is a bit of a conundrum for me. He clearly know a lot,
>>but
>>his "blameless amp" is not the "best/optimum" architecture in my view, if
>>"best/optimum" can actually be defined. His second stage is not
>>differential, and uses a fixed constant current load. A differential,
>>current mirror loaded second stage gives inherent lower distortion for
>>that
>>second stage, and gives a somewhat "better" push pull drive to the next
>>stage. A fixed current load mean that the gain transistor is always
>>tugging
>>at that current source.

>He actually talks about the advantages and disadvantages of making the
>second stage differential in tha latest edition of his book. He claims it
>doesn't actually buy a reduction in distortion in the long run.

I am a great believer in differential whenever possible. In principle, it
can help with the issue you note above about distortion on the PS rails. I
also prefer the push/pull drive to the buffer stages that such a topology
gives.

> He is an
>odd character and he is set in his ways in a lot of cases, but although he
>sometimes has bizarre opinions he always has good numbers to back them up.


Actually, I just discovered he lists me twice on his "notable letters to
Electronics World" section at:

http://www.douglas-self.com/ampins/library/lettersWW.htm


Kevin Aylward B.Sc.
www.kevinaylward.co.uk

[Kevin Aylward[_4_]]

"anahata" wrote in message
...

On Wed, 02 Feb 2011 15:17:27 +0000, Kevin Aylward wrote:
>>
>> an amplifier needs to be designed such that it can reach its rated power
>> into a rated impedance e.g. 4 ohms or 8 ohms.

>With some amplifiers that only works for a pure resistive load.

Well, a poor amplifier might current limit at say, 20% above rated output,
but realistically I don't think that is a "competent" design. In practice,
one needs a certain margin just to account for component tolerances.

>> By construction, speakers
>> rated at say, 4 ohm should have a minimum resistance of 4 ohms.
>> Typically they may be a bit larger, e.g. 4.5.

Sure, a speaker might be as low as 3 ohms for a 4 ohm rating, possibly.
Although wiring it up might well add a 0.1 - 0.5 ohms or so.

>In practice, the crossover/speaker combination often goes below the
>nominal impedance of the speaker. For a start, the DC resistance is
>usually less, but the RC network may present a low impedances at one
>frequency.

Actually, very very, unlikely for small signal impedance of the speaker
itself. I have never seen a plot of loudspeaker impedance go below its DC
resistance. However, with specific pulse wave shapes applied, pulse currents
larger than that implied by V/Rdc can still occur.

Its debatable just what the max pulse can be. One has to time an
asymmetrical waveform just right to get the real peak, which theoretically
could be quite a large ratio. In practice, music signals just don't have the
right characteristics to do this.

>> However, a decent amp
>> always has a certain amount of transient overload current available. My
>> mosfet 1000 could do about twice rated current continuously, until the
>> thermal came in.

>That's good conservative design, but not always found in commercially
>available amplifiers. I've seen (and heard!) a supposedly professional
>grade power amplifier go into foldback limiting with a speaker whose
>impedance was very reactive at some frequencies.

I am not an advocate of VI limiters. I prefer a hard current limit, with
thermal cut-out.

>This is all beside the point though, as I think Paul was suggesting
>audible LF artifacts appearing at the output as a result, perhaps, of
>power supply or bias chain modulation, not failure of the amplifier to
>deliver the required current. If a repeated mid/HF toneburst causes
>thumping noises in the speakers, that's a kind of distortion, but it's
>not necessarily caused by current limiting, and nor can it be revealed by
>steady state tone tests.

It can be revealed by simple, easily available pulse wave forms though, e.g.
burst sine and square. My point is that there is nothing magic about music
signals. Everything of relevance can be tested with standard test equipment.


Kevin Aylward B.Sc.
www.kevinaylward.co.uk

[Scott Dorsey]

Kevin Aylward > wrote:
>"Scott Dorsey" wrote in message ...
>
>>The problem is that it builds up. You get .001% distortion from a coupling
>>cap, then you put a couple hundred of them in the signal path and the end
>>result is a lot of distortion. Not a huge issue for a small power amp but
>>a big one for a mixing console.
>
>Well, 100 in in the path is a probably bit of an over estimate, no one
>really wants to spend that sort of build cost, but sure, no one sets the
>turnover at 20Hz if the whole system is to be specked at 20Hz - 20Khz +/-1db
>anyway.

Try around 220 in an SSL 4000 with a typical configuration. That includes
mike in, channel strip, master module, send, return, channel strip,
master module, and main out. This is how the problems build up. Every
op-amp module has a little distortion, every op-amp has a blocking cap,
and the problems blow up.

I was with an AES tour of the mastering room at Brooklyn Phono, and
one of the fellows in the tour of an audiophile nature asked the
mastering engineer about the Neumann cutting amps. "Are there any
capacitors in the signal path?" Paul, the engineer went blank for
a second just at the nature of the question. "Oh yeah, there must be
a million of them" he said. A million is exaggerating, but there are
a whole lot of stages in there and they are all AC-coupled.

>And that's my point. I don't suggest a single point at full output. One
>needs at least two points to include a value that reflects x-over
>distortion. One also needs to know that the amp does not have some
>pathological behaviour that makes an implication of performance not actually
>specified, false.

If you're going to do that, why not just look at a full spectrum? It
tells you so much more information.

>I don't think anyone really cares today about the numbers for the area I am
>interested in. i.e. P.A amplifiers for live band work. Many manufactures
>don't quote any/many numbers nowadays. 30 years ago, it was more of a
>numbers game. Today, most commercial PA amplifiers are worse than that was
>achieved 30 years ago.

Well, in that application, speaker distortion levels are still insanely
high, too. And, issues like efficiency and shipping weight become paramount
in ways that they are not for studio amplifiers.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Kevin Aylward[_4_]]

"Scott Dorsey" wrote in message ...

Kevin Aylward >> wrote:
>>"Scott Dorsey" wrote in message ...
>>
>>>>The problem is that it builds up. You get .001% distortion from a
>>>>coupling
>>>>cap, then you put a couple hundred of them in the signal path and the
>>>>end
>>>>result is a lot of distortion. Not a huge issue for a small power amp
>>>>but
>>>>a big one for a mixing console.
>>
>>Well, 100 in in the path is a probably bit of an over estimate, no one
>>really wants to spend that sort of build cost, but sure, no one sets the
>>turnover at 20Hz if the whole system is to be specked at 20Hz - 20Khz
>>+/-1db
>>anyway.

>Try around 220 in an SSL 4000 with a typical configuration. That includes
>mike in, channel strip, master module, send, return, channel strip,
>master module, and main out.

???

That's 8. What else that can add up to 220 ?

Anyway...

>This is how the problems build up. Every
>op-amp module has a little distortion, every op-amp has a blocking cap,
>and the problems blow up.

Sure there is a build up, in principle. In fact, it was a basic problem in
analogue telephony in the 20s-30s. It was, pretty much why feedback was
invented by Black at Bell labs. To get the final 5% - 10% crap distortion we
all love, when the phone system goes through 100s of repeaters, needed <
0.01% distortion for each amplifier, and this at 60Khz-120Khz modulated
carrier frequencies.

>>And that's my point. I don't suggest a single point at full output. One
>>needs at least two points to include a value that reflects x-over
>>distortion. One also needs to know that the amp does not have some
>>pathological behaviour that makes an implication of performance not
>>actually
>>specified, false.

>If you're going to do that, why not just look at a full spectrum? It
>tells you so much more information.

The point is that, by and large, HF always has the most distortion i.e. the
max distortion. If this max is low enough, then its superfluous what it
actually is at lower frequencies as it will be lower.

Of course, in practice one does do tests at all frequencies as a check.

Actually, today with the extremely, extremely expensive Cadence software I
use at work in my day job, physical measurements are also quite superfluous.
One can design completely in the virtual world, and I usually do. Running a
Spectre R.F. steady state transient analysis using either harmonic balance
or shooting method, can take less than a minute on a full amplifier to
obtain full frequency spectrums of distortion, and THD and IMD and time
domain plots. I wish I had access to this kit 30 years ago. Its truly
wonderful. e.g. running parameter sweeps of AB bias current and emitter
resisters all in one go. Simulation tools have really came a long way.
Unfortunately, my own SuperSpice (www.anasoft.co.uk) does not do these
methods. Getting distortion by the usual methods needs really long transient
runs.

>>I don't think anyone really cares today about the numbers for the area I
>>am
>>interested in. i.e. P.A amplifiers for live band work. Many manufactures
>>don't quote any/many numbers nowadays. 30 years ago, it was more of a
>>numbers game. Today, most commercial PA amplifiers are worse than that was
>>achieved 30 years ago.

>Well, in that application, speaker distortion levels are still insanely
>high, too. And, issues like efficiency and shipping weight become
>paramount
>in ways that they are not for studio amplifiers.


Indeed, that is exactly my current priority. I want a loud, light and small
speaker system to fit my MPV car. Its the thing I dislike the most about
doing gigs. Carrying gear, and trying to pack it all in.

Regards

Kevin Aylward B.Sc.

www.kevinaylward.co.uk

[Scott Dorsey]

Kevin Aylward > wrote:
>"Scott Dorsey" wrote in message ...
>
>>Try around 220 in an SSL 4000 with a typical configuration. That includes
>>mike in, channel strip, master module, send, return, channel strip,
>>master module, and main out.
>
>???
>
>That's 8. What else that can add up to 220 ?

Each one of those sections has a dozen or two op-amps in the signal path,
in part because there's a whole lot of fancy routing stuff in there. Nobody
every got an SSL because it sounded good, they got it because it had very
powerful routing.

>>This is how the problems build up. Every
>>op-amp module has a little distortion, every op-amp has a blocking cap,
>>and the problems blow up.
>
>Sure there is a build up, in principle. In fact, it was a basic problem in
>analogue telephony in the 20s-30s. It was, pretty much why feedback was
>invented by Black at Bell labs. To get the final 5% - 10% crap distortion we
>all love, when the phone system goes through 100s of repeaters, needed <
>0.01% distortion for each amplifier, and this at 60Khz-120Khz modulated
>carrier frequencies.

Precisely. It's not a new problem.

>>>And that's my point. I don't suggest a single point at full output. One
>>>needs at least two points to include a value that reflects x-over
>>>distortion. One also needs to know that the amp does not have some
>>>pathological behaviour that makes an implication of performance not
>>>actually
>>>specified, false.
>
>>If you're going to do that, why not just look at a full spectrum? It
>>tells you so much more information.
>
>The point is that, by and large, HF always has the most distortion i.e. the
>max distortion. If this max is low enough, then its superfluous what it
>actually is at lower frequencies as it will be lower.

I worry about all measurable products, because as mentioned above they have
a tendency to build up throughout the signal chain. Also I worry about things
like amplifiers because they need to be measured with an actual real-world
load and they usually are not.

>Actually, today with the extremely, extremely expensive Cadence software I
>use at work in my day job, physical measurements are also quite superfluous.
>One can design completely in the virtual world, and I usually do. Running a
>Spectre R.F. steady state transient analysis using either harmonic balance
>or shooting method, can take less than a minute on a full amplifier to
>obtain full frequency spectrums of distortion, and THD and IMD and time
>domain plots. I wish I had access to this kit 30 years ago. Its truly
>wonderful. e.g. running parameter sweeps of AB bias current and emitter
>resisters all in one go. Simulation tools have really came a long way.
>Unfortunately, my own SuperSpice (www.anasoft.co.uk) does not do these
>methods. Getting distortion by the usual methods needs really long transient
>runs.

Simulation gives me the willies. It's good for a first cut design, but
every time I have dealt with a simulated design it has always needed some
tweaking when actually implemented, because the simulation is never quite
faithful.

On the other hand, it's possible to do simulations and see what the
consequences of part variations are very easily, and it's hard to do that
in the real world without actually going into production.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Kevin Aylward[_4_]]

"Scott Dorsey" wrote in message ...


>>Actually, today with the extremely, extremely expensive Cadence software I
>>use at work in my day job, physical measurements are also quite
>>superfluous.
>>One can design completely in the virtual world, and I usually do. Running
>>a
>>Spectre R.F. steady state transient analysis using either harmonic balance
>>or shooting method, can take less than a minute on a full amplifier to
>>obtain full frequency spectrums of distortion, and THD and IMD and time
>>domain plots. I wish I had access to this kit 30 years ago. Its truly
>>wonderful. e.g. running parameter sweeps of AB bias current and emitter
>>resisters all in one go. Simulation tools have really came a long way.
>>Unfortunately, my own SuperSpice (www.anasoft.co.uk) does not do these
>>methods. Getting distortion by the usual methods needs really long
>>transient
>>runs.

I should clarify, class B x-over distortion is problematic without periodic
steady state analysis. General class A, small signal distortion is perfectly
ok in spice.

>Simulation gives me the willies. It's good for a first cut design, but
>every time I have dealt with a simulated design it has always needed some
>tweaking when actually implemented, because the simulation is never quite
>faithful.

I have to disagree here. I design relatively complex analogue/mixed mode
system on chip i.c.s. It might have say 10,000 analogue transistors, doing
all sorts of things. Mask and fab costs (> $100k) and turnaround times ( > 2
months ) are such that the chips need to be fully functional 1st time pass,
and production ready second time pass. This is indeed usually achieved as
the norm. In fact, its not unknown to get 2% of sales (say $10M) bonus for a
1st time production ready pass!

My experience is that errors occur, not because of simulation errors, but
simply because a certain simulation was not run at all, or a specification
was overlooked. Models and tools are so good nowadays, that the often quoted
tweaking on the bench is simply not necessary, and impossible for an ic
design. I haven't bench tweaked a design for over 20 years. I have found
faults on the bench, but I have always been able to replicate them in
simulation, and fix them entirely in the virtual world.

>On the other hand, it's possible to do simulations and see what the
>consequences of part variations are very easily, and it's hard to do that
>in the real world without actually going into production.

Yes.

Kevin Aylward B.Sc.
www.kevinaylward.co.uk