[Patrick Turner]

Eeyore wrote:

Patrick Turner wrote:

Ian Iveson wrote:
zyx wrote

I have an epi valve jr combo with 8" speaker that is 4 ohms. I want
to try it on a 12" speaker which is 8 ohms.

Jam away?

A bit risky. Anode voltage may rise higher than some parts can cope
with reliably.

As a general rule, SS amps don't care too much about a higher load
impedance, and valves are tolerant of a lower one.

SS amps have a load of NFB and there is a Zobel network which loads the
output, and there is no OPT, so no high voltages with no load, and supply
voltages are lower anyway,

Not to mention diodes fron output to supply rails too.

Graham

But I went on to say how inductive speaker loads on an SS amp could give
rise to destructive back emfs.

SS amps need all the protection they can get.

Patrick Turner.

[Patrick Turner]

Eeyore wrote:

Patrick Turner wrote:

Eeyore wrote:
Ian Iveson wrote:
zyx wrote

I have an epi valve jr combo with 8" speaker that is 4 ohms. I want
to try it on a 12" speaker which is 8 ohms.

Jam away?

A bit risky. Anode voltage may rise higher than some parts can cope
with reliably.

Oh puhleeze ! Is that nonsense or what ?

As a general rule, SS amps don't care too much about a higher load
impedance, and valves are tolerant of a lower one.

Tolerant to a point ! I wouldn't advise it. In fact I doubt any valve amps will
drive a 1 - 2 ohms load very well, yet many SS amps do it admirably.

Graham

Tube amps can be load matched to allow any low value load to be
connected since there is an OPT which may have adjustable configurations
of windings.

I had in mind the 'typical' 4, 8 and 16 ohm taps on most power amplifiers.

Have you ever seen a 2 ohm tap btw ?

Graham

What I said in my other posts on the subject was that many old amps have
a pair of
2 ohm windings. When seriesed, you get a match for 8 ohms, because there
are twice the turns on the sec,
and 2 squared = 4, so 2 ohms becomes 8 ohms.

When paralleled, you still only get 2 ohms, since there is no difference
to the turn count.

But many old amps were meant for 4 or 16 ohms by juggling the two lousy
windings offered.
It was either 4 or 16, and having 8 ohms meant the windings had to be
divided awkwardly, and awkward extra
matches cost extra money, so it rarely happened properly.
The 4 or 16 was for for NOMINAL MATCHES of course, never literally,
and usually the nominal meant you had 10k : 16 ohms for 20 watts of
class A, or for anything over
8 ohms for class AB, or 10K : 4 ohms, for class A, or for anything
between 2 and 4 giving acceptable class AB.

To repeat, the 16 ohms configuration meant you could possibly have 5k
a-a : 8 ohms for class AB,
or if the 8 ohms was connected to the two paralleled 4 ohm windings
you'd get 20k a-a as the load,
and a "low distortion, low power class A connection, with low output
resistance".
You could connect 4 ohms to the 4 ohm config for class A but 2 ohms
worked fine since the a-a
load only dropped to 5k a-a, and still drivable by an average pair of
6L6/KT66;
;if more power into lower loads is needed use KT88/KT90.

The OPT is a like an electronic gear box which allows you to drive up
any hill no matter how steep.

Remember the fundementals.

More basic/not so basic info is at http://www.turneraudio.com.au

Patrick Turner.

[Patrick Turner]

Eeyore wrote:

Phil Allison wrote:

"Eeysore the Raving CRIMINAL LUNATIC" "

" Normal operation ( for a guitar amp) is the case. "

Ok - so *how easily* ?

** The question has been answered.

Do your own tests if you want proof.

Do a GG search on " alt .guitar.amps" on the topic of "flyback
spikes
"
for confirmation the phenomenon is well known.


So you're just making it up ( you can't or refuse to explain it ).

** What an UTTER non sequitur !!!!!!!!

So go-on, what causes the 5kV ?

** So you have no idea what the term " flyback spikes" refers to ?

I know exactly.


But you do now accept that they really exist in valve amps ???

If the load's disconnected for sure.


** Err - what about inductive loads ??

Like guitar speaker cabs ??

Finally did a little Googling - did we ?

No need.

** But I bet you did so anyhow - LIAR !!

I didn't. As I said - simply no need.

Now, how did *YOU* get 5kV flyback spikes.

What was the load ?

** A quad box, 4 x Celestion 12 inch, wired series /parallel.

An 8 or 16 ohm dummy load with series inductor of a few mH simulates the
above.

How hard was the amp being driven ?

** Full overdrive / clipping.

Just like most guitarist play their Marshalls for hours on end.

What was the input signal ?

** A slide guitarist with his Gibson SG demonstrated in one case.

A sine wave bench gen does nicely too.

So why didn't you just say this when I originally asked ?

BTW :

I don't expect a VILE CRIMINAL LUNATIC

like Graham Stevenson to accept a single word of this.

He did not ask me in order to find out the facts.

Having done NO such tests himself - he has not the SLIGHTEST clue about
it.

He will never do any either.

I do accept it. In fact I accepted it when you first posted it if you bother to
check.

What I said in fact was that if you can create 5kV spikes with the *correct*
load, then changing it from 4 to 8 ohms isn't going to change that.

Without any load connected, perhaps 5kV spikes are possible.
With loading of say 20 ohms on an amp with 5k:8 ZR ratio, it is
impossible to have such HV spikes.
Loading the amp DOES change the ability of the amp to make 5 kV spikes.

Measure and observe an amp Graham, and all will be revealed....

Be careful how you measure the HV, lest you blow crap out of your
voltmeter.


Patrick Turner.

Graham

[Patrick Turner]

Eeyore wrote:

Patrick Turner wrote:

What is NEVER fitted to an SS amp is an intelligent circuit that detects
if the load
is below 2 ohms and TURNS THE AMP OFF even if it is used at low level.
This safety option would save all the amps who expire when connected to
shorted speaker cables
or to fried/faulty speakers/crossovers.

Actually QSC have a very crude system that does do this.
http://www.freepatentsonline.com/4321554.html

What is the URL for the schematic?

Patrick Turner.

It's an area I've been looking into myself actually as it can hugely benefit
amplifier design by eliminating 'hard' current limiting.

Graham

[Patrick Turner]

John Byrns wrote:

In article ,
Patrick Turner wrote:

So regardless of what you say Lord V, there is always a risk of arcing
at the tube sockets
because there is so little ever done to prevent it, like say
having diodes connected from each anode to ground, to prevent the Vswing
ever moving negative with respect to 0V, and thus prevent Eamax ever
swinging more than twice
the supply voltage.

You are assuming the transformer has no leakage inductance between
primary halves, is this a valid assumption for the typical guitar amp?

The leakage inductance between halves of guitar amp OPTs is usually
high, but
nevertheless the negative going voltages which are shunted are arrested
by the diodes, and the positive going
voltages at the other end of the primary are also arrested..
And BTW, really high power tube amps for say 1,000 watts+ using
anode supply voltages of say 2.5kV and high ohm anode loads used spark
gaps adjusted so excess voltage would be
harmlessly shunted in a spark. Usually OPT were mounted in a sealed box
full of oil with ceramic stand off connections.
This does not appear in Fender or Marshall.

Back emfs are a fact of life...

Patrick Turner.

Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[Eeyore]

Phil Allison wrote:

The typical product design engineer never gets involved with repairs, even
to his own designs, gets little or no feedback from the field unless a very
serious failure situation arises. They are normally quite unwilling to
accept any input or criticism from ANY folk involved in the repair business
and especially not from other designers.

That must make me very different then.

I positively ecourage feedback from service guys.

Graham

[Eeyore]

Patrick Turner wrote:

Eeyore wrote:
Phil Allison wrote:
"Eeysore the Raving CRIMINAL LUNATIC" "

" Normal operation ( for a guitar amp) is the case. "

Ok - so *how easily* ?

** The question has been answered.

Do your own tests if you want proof.

Do a GG search on " alt .guitar.amps" on the topic of "flyback
spikes
"
for confirmation the phenomenon is well known.


So you're just making it up ( you can't or refuse to explain it ).

** What an UTTER non sequitur !!!!!!!!

So go-on, what causes the 5kV ?

** So you have no idea what the term " flyback spikes" refers to ?

I know exactly.

But you do now accept that they really exist in valve amps ???

If the load's disconnected for sure.

Finally did a little Googling - did we ?

No need.

Now, how did *YOU* get 5kV flyback spikes.

What was the load ?

How hard was the amp being driven ?

What was the input signal ?

Graham

Graham, no need to react against Allison's poor manners which are a
response to your
inability to understand that perhaps 5,000V is possible in a guitar amp
without a load.

I had no problem understanding the issue with no load !

His assertion was that you can get 5000V spikes wuith the *correct rated
impedance connected*.


Try measuring one, and you will find out all about.

Very much higher signal voltages anode to anode ARE generated by an
unloaded pentode/beam tetrode
output stage than the normal working loaded voltages.

This wasn't about *unloaded* working Patrick.

Graham

[Eeyore]

Patrick Turner wrote:

Eeyore wrote:
Phil Allison wrote:
"Eeysore the Raving CRIMINAL LUNATIC" "

" Normal operation ( for a guitar amp) is the case. "

Ok - so *how easily* ?

** The question has been answered.

Do your own tests if you want proof.

Do a GG search on " alt .guitar.amps" on the topic of "flyback
spikes
"
for confirmation the phenomenon is well known.


So you're just making it up ( you can't or refuse to explain it ).

** What an UTTER non sequitur !!!!!!!!

So go-on, what causes the 5kV ?

** So you have no idea what the term " flyback spikes" refers to ?

I know exactly.


But you do now accept that they really exist in valve amps ???

If the load's disconnected for sure.


** Err - what about inductive loads ??

Like guitar speaker cabs ??

Finally did a little Googling - did we ?

No need.

** But I bet you did so anyhow - LIAR !!

I didn't. As I said - simply no need.

Now, how did *YOU* get 5kV flyback spikes.

What was the load ?

** A quad box, 4 x Celestion 12 inch, wired series /parallel.

An 8 or 16 ohm dummy load with series inductor of a few mH simulates the
above.

How hard was the amp being driven ?

** Full overdrive / clipping.

Just like most guitarist play their Marshalls for hours on end.

What was the input signal ?

** A slide guitarist with his Gibson SG demonstrated in one case.

A sine wave bench gen does nicely too.

So why didn't you just say this when I originally asked ?

BTW :

I don't expect a VILE CRIMINAL LUNATIC

like Graham Stevenson to accept a single word of this.

He did not ask me in order to find out the facts.

Having done NO such tests himself - he has not the SLIGHTEST clue about
it.

He will never do any either.

I do accept it. In fact I accepted it when you first posted it if you bother to
check.

What I said in fact was that if you can create 5kV spikes with the *correct*
load, then changing it from 4 to 8 ohms isn't going to change that.

Without any load connected, perhaps 5kV spikes are possible.
With loading of say 20 ohms on an amp with 5k:8 ZR ratio, it is
impossible to have such HV spikes.

That was what I said myself.


Loading the amp DOES change the ability of the amp to make 5 kV spikes.

Measure and observe an amp Graham, and all will be revealed....

No need. I've been in agreement with you all along.


Be careful how you measure the HV, lest you blow crap out of your
voltmeter.

You'd need a scope to see the flyback spikes not a voltmeter.

Graham

[Eeyore]

Patrick Turner wrote:

Eeyore wrote:
Patrick Turner wrote:
Ian Iveson wrote:
zyx wrote

I have an epi valve jr combo with 8" speaker that is 4 ohms. I want
to try it on a 12" speaker which is 8 ohms.

Jam away?

A bit risky. Anode voltage may rise higher than some parts can cope
with reliably.

As a general rule, SS amps don't care too much about a higher load
impedance, and valves are tolerant of a lower one.

SS amps have a load of NFB and there is a Zobel network which loads the
output, and there is no OPT, so no high voltages with no load, and supply
voltages are lower anyway,

Not to mention diodes fron output to supply rails too.

Graham

But I went on to say how inductive speaker loads on an SS amp could give
rise to destructive back emfs.

SS amps need all the protection they can get.

I don't think they're *inherently* any more fragile to be honest.

Graham

[Eeyore]

Patrick Turner wrote:

Eeyore wrote:

Patrick Turner wrote:

What is NEVER fitted to an SS amp is an intelligent circuit that detects
if the load
is below 2 ohms and TURNS THE AMP OFF even if it is used at low level.
This safety option would save all the amps who expire when connected to
shorted speaker cables
or to fried/faulty speakers/crossovers.

Actually QSC have a very crude system that does do this.
http://www.freepatentsonline.com/4321554.html

What is the URL for the schematic?

http://patft.uspto.gov/netacgi/nph-P...&RS=PN/4321554

and click on images.

Graham

[tubegarden]

Eeyore wrote:

I positively ecourage feedback from service guys.

Graham


Hi RATs!

Good plan Not everyone can spec the only noisey resistor ever
manufactured ... I am not surprised you didn't notice :^P

Happy Ears!
Al

[Phil Allison]

"Ian Iveson = INSANE POMMY PRICK "



** This insanely demented, criminal pommy **** needs shooting.








......... Phil

[Phil Allison]

"Eeysore the ****WIT POMMY **** "



The typical product design engineer never gets involved with repairs,
even
to his own designs, gets little or no feedback from the field unless a
very
serious failure situation arises. They are normally quite unwilling to
accept any input or criticism from ANY folk involved in the repair
business
and especially not from other designers.

That must make me very different then.


** ROTFL !!!


YOU are the VERY WORST example on earth.

An utterly manic, know nothing, ASD ****ed, criminal pommy psychopath &
blatant charlatan.

Jail is where Graham Stevenson should be.




........ Phil

[Sander deWaal]

"Phil Allison" said:


"Sander deWaal"


Repair experience is probably even more useful, one gets to see all
different kinds of amps, topologies and failures.

One can get a very good insight about the weak spots in designs by a
lifelong career in repairing various audio gear.


** But ONLY if that technician is * insatiably curious* about audio
electronics and puts in the time and considerable mental effort to analyse
nearly every circuit & component failure scenario they come across.

The vast majority of service techs are not allowed ( even if they wanted to)
to indulge in such time consuming, non profit making activity when there is
other work waiting to be done and a prowling boss to keep happy.

Only independent, self employed techs who are not too overworked might do as
you suggest, even then only if they have the required technical ability.

The typical product design engineer never gets involved with repairs, even
to his own designs, gets little or no feedback from the field unless a very
serious failure situation arises. They are normally quite unwilling to
accept any input or criticism from ANY folk involved in the repair business
and especially not from other designers.

This of course condemns them to repeating their dumbest mistakes - which
are then mass produced, sold to a gullible marketplace and ultimately left
to mere repair techs to eventually unravel & attempt to find fixes for.

I have many times wished I could deliver some expensive pile of audio
garbage back to the doorstep of the utter ass who is responsible for it and
say - " you designed this POS - so you bloody fix it " !!

....... Phil


Agreed in full, Phil.

I must have been lucky for over 25 years, because I always managed to
learn something from the repairs I did, and it proved extremely useful
in my design career.

--

- Maggies are an addiction for life. -

[Arny Krueger]

"Phil Allison" wrote in message

"Arny Krueger"


" Ironically, if one takes Phil's advice and searches
alt.guitar.amps for posts about flyback spikes, you find
him dodging the same basic question you asked about
generating 5 Kv spikes around 2/25/2003, for example. "

** No - it is 6 days earlier & cannot be in the same
thread as Arny is saying.


I specified no particular thread, Phil.


** You specified a date and a * particular * line of
content.

No, I specified a range of dates and a general line of content.

[Phil Allison]

"Arny Krueger "
"Phil Allison"

" Ironically, if one takes Phil's advice and searches
alt.guitar.amps for posts about flyback spikes, you find
him dodging the same basic question you asked about
generating 5 Kv spikes around 2/25/2003, for example. "

** No - it is 6 days earlier & cannot be in the same
thread as Arny is saying.


I specified no particular thread, Phil.


** You specified a date and a * particular * line of
content.


No, I specified a range of dates and a general line of content.


** You specified a date and claimed a * particular * line of content was
there - but not a shred of evidence to back up your ****wit assertion.

That is a worse dishonesty than from ANY of the audiophools you so like to
torment.


Go get totally ****ED you MONSTROUSLY EVIL HYPOCRITE





......... Phil

[Phil Allison]

"Sander deWaal"
"Phil Allison"



Repair experience is probably even more useful, one gets to see all
different kinds of amps, topologies and failures.

One can get a very good insight about the weak spots in designs by a
lifelong career in repairing various audio gear.


** But ONLY if that technician is * insatiably curious* about audio
electronics and puts in the time and considerable mental effort to analyse
nearly every circuit & component failure scenario they come across.

The vast majority of service techs are not allowed ( even if they wanted
to)
to indulge in such time consuming, non profit making activity when there
is
other work waiting to be done and a prowling boss to keep happy.

Only independent, self employed techs who are not too overworked might do
as
you suggest, even then only if they have the required technical ability.

The typical product design engineer never gets involved with repairs,
even
to his own designs, gets little or no feedback from the field unless a
very
serious failure situation arises. They are normally quite unwilling to
accept any input or criticism from ANY folk involved in the repair
business
and especially not from other designers.

This of course condemns them to repeating their dumbest mistakes - which
are then mass produced, sold to a gullible marketplace and ultimately left
to mere repair techs to eventually unravel & attempt to find fixes for.

I have many times wished I could deliver some expensive pile of audio
garbage back to the doorstep of the utter ass who is responsible for it
and
say - " you designed this POS - so you bloody fix it " !!


Agreed in full, Phil.


** Just stating the facts - mam.



I must have been lucky for over 25 years, because I always managed to
learn something from the repairs I did, and it proved extremely useful
in my design career.


** Trouble shooting a defective item ( particularly one with design flaws)
and carrying out repairs efficiently is an UTTERLY different process to
doing product design work.

If all product designers were FORCED to regularly do component level repair
work on their OWN designs - I reckon their would be far fewer seriously
flawed and repair hostile products dumped on the world.

It is only because factories that mass produce stuff * rarely if ever *
have products come back to them to be put right that this continues to
happen.




........ Phil

[Patrick Turner]

Eeyore wrote:

Patrick Turner wrote:

Eeyore wrote:
Patrick Turner wrote:
Ian Iveson wrote:
zyx wrote

I have an epi valve jr combo with 8" speaker that is 4 ohms. I want
to try it on a 12" speaker which is 8 ohms.

Jam away?

A bit risky. Anode voltage may rise higher than some parts can cope
with reliably.

As a general rule, SS amps don't care too much about a higher load
impedance, and valves are tolerant of a lower one.

SS amps have a load of NFB and there is a Zobel network which loads the
output, and there is no OPT, so no high voltages with no load, and supply
voltages are lower anyway,

Not to mention diodes fron output to supply rails too.

Graham

But I went on to say how inductive speaker loads on an SS amp could give
rise to destructive back emfs.

SS amps need all the protection they can get.

I don't think they're *inherently* any more fragile to be honest.

Graham

I am one of many technicians in my small city of 300,000 souls who
make a living repairing solid state crap.

Electronic products are NOT as rugged as they could or should be.

Patrick Turner.

[Patrick Turner]

Eeyore wrote:

Patrick Turner wrote:

Eeyore wrote:

Patrick Turner wrote:

What is NEVER fitted to an SS amp is an intelligent circuit that detects
if the load
is below 2 ohms and TURNS THE AMP OFF even if it is used at low level.
This safety option would save all the amps who expire when connected to
shorted speaker cables
or to fried/faulty speakers/crossovers.

Actually QSC have a very crude system that does do this.
http://www.freepatentsonline.com/4321554.html

What is the URL for the schematic?

http://patft.uspto.gov/netacgi/nph-P...&RS=PN/4321554

and click on images.

Graham

This does not work.

I went to the above site, and it asked me to click for a
plug in which failed to work.

If you give a URL of a schematic, please be SO KIND
to make completely sure that it is a ONE CLICK journey.

Patrick Turner.

[Phil Allison]

"Patrick Turner"

Sensible SS guitar amps
have diodes from the output to
the rails to prevent swings on the output ever going more than the rail
voltage peak value,
since this can occur with the inductive load of a speaker, and cause
instant death to the output
bjts with reverse flow currents.


** Plenty of reliable BJT SS guitar and hi-fi amps have no such diodes.

( MOSFETS have such reverse diodes inherent inside the device.)

The need for "flyback diodes" only arises when the particular BJT amp
incorporates VI limiting circuitry to protect output devices from over
dissipation and SOA induced failures.

See: http://sound.westhost.com/vi.htm




........ Phil

[Patrick Turner]

Eeyore wrote:

Patrick Turner wrote:

Eeyore wrote:
Phil Allison wrote:
"Eeysore the Raving CRIMINAL LUNATIC" "

" Normal operation ( for a guitar amp) is the case. "

Ok - so *how easily* ?

** The question has been answered.

Do your own tests if you want proof.

Do a GG search on " alt .guitar.amps" on the topic of "flyback
spikes
"
for confirmation the phenomenon is well known.


So you're just making it up ( you can't or refuse to explain it ).

** What an UTTER non sequitur !!!!!!!!

So go-on, what causes the 5kV ?

** So you have no idea what the term " flyback spikes" refers to ?

I know exactly.


But you do now accept that they really exist in valve amps ???

If the load's disconnected for sure.


** Err - what about inductive loads ??

Like guitar speaker cabs ??

Finally did a little Googling - did we ?

No need.

** But I bet you did so anyhow - LIAR !!

I didn't. As I said - simply no need.

Now, how did *YOU* get 5kV flyback spikes.

What was the load ?

** A quad box, 4 x Celestion 12 inch, wired series /parallel.

An 8 or 16 ohm dummy load with series inductor of a few mH simulates the
above.

How hard was the amp being driven ?

** Full overdrive / clipping.

Just like most guitarist play their Marshalls for hours on end.

What was the input signal ?

** A slide guitarist with his Gibson SG demonstrated in one case.

A sine wave bench gen does nicely too.

So why didn't you just say this when I originally asked ?

BTW :

I don't expect a VILE CRIMINAL LUNATIC

like Graham Stevenson to accept a single word of this.

He did not ask me in order to find out the facts.

Having done NO such tests himself - he has not the SLIGHTEST clue about
it.

He will never do any either.

I do accept it. In fact I accepted it when you first posted it if you bother to
check.

What I said in fact was that if you can create 5kV spikes with the *correct*
load, then changing it from 4 to 8 ohms isn't going to change that.

Without any load connected, perhaps 5kV spikes are possible.
With loading of say 20 ohms on an amp with 5k:8 ZR ratio, it is
impossible to have such HV spikes.

That was what I said myself.

Loading the amp DOES change the ability of the amp to make 5 kV spikes.

Measure and observe an amp Graham, and all will be revealed....

No need. I've been in agreement with you all along.

Be careful how you measure the HV, lest you blow crap out of your
voltmeter.

You'd need a scope to see the flyback spikes not a voltmeter.

Graham

Just using a 1 kHz sine wave turned up on a pentode PP amp
with no load will measure a HV on any high Z input of any DVM.
These meters are commonly limited to 750Vrms measurement,
and so a 1,500Vrms voltage a-a will blow the meter regardless of whether
you can see it
on the CRO or not.
Just when you expect the wave form to clip, its amplitude just gets
greater by perhaps 10dB, ( 3 times )
and I always back off....
So stray noise clicks, whatever, could cause huge spikes....

One should use a 1:10 reduction probe well rated for HV when measuring
anode to anode voltages
with a meter or viewing such voltages on the CRO.
I once subjected a CRO to 2,000V ( estimated ) pulse, and it was a
costly
and time consuming experience to repair or replace nearly every chip in
the CRO, a Labtech,
full of 14 pin chips.

I now use a far simpler single trace CRO with discrete bjts which is
expendable in the event of
over-voltaging, and its lasted 5 years OK without too many special
precautions.

Patrick Turner.

[Phil Allison]

"Patrick Turner"


What is the URL for the schematic?

http://patft.uspto.gov/netacgi/nph-P...&RS=PN/4321554

and click on images.


This does not work.


** Forget it - it is all incomprehensible drivel anyhow.

Masses of brain numbing verbiage written in the usual pseudo-legal lingo of
a patent app.


BTW

I know the scheme as it is used in a few QSC power amplifiers - ie the USA
series.

Those amps completely * self destruct * if ever asked to drive a
saturating transformer load.




......... Phil

[Arny Krueger]

"Patrick Turner" wrote in message

Eeyore wrote:

Patrick Turner wrote:

Eeyore wrote:

Patrick Turner wrote:

What is NEVER fitted to an SS amp is an intelligent
circuit that detects if the load
is below 2 ohms and TURNS THE AMP OFF even if it is
used at low level. This safety option would save all
the amps who expire when connected to shorted speaker
cables
or to fried/faulty speakers/crossovers.

Actually QSC have a very crude system that does do
this. http://www.freepatentsonline.com/4321554.html

What is the URL for the schematic?

http://patft.uspto.gov/netacgi/nph-P...&RS=PN/4321554

and click on images.

Graham

This does not work.

Works for me - perfectly!

I went to the above site, and it asked me to click for a
plug in which failed to work.

Update Quicktime on your computer.

[Arny Krueger]

"Phil Allison" wrote in message

"Arny Krueger "
"Phil Allison"

" Ironically, if one takes Phil's advice and searches
alt.guitar.amps for posts about flyback spikes, you find
him dodging the same basic question you asked about
generating 5 Kv spikes around 2/25/2003, for example. "

** No - it is 6 days earlier & cannot be in the
same thread as Arny is saying.


I specified no particular thread, Phil.


** You specified a date and a * particular * line of
content.


No, I specified a range of dates and a general line of
content.


** You specified a date

I said "around".

and claimed a * particular * line of content was there

No, general - you dodging an general question.

- but not a shred of
evidence to back up your ****wit assertion.

Never heard of google groups advanced search, I take it.

[Phil Allison]

"Arny Krueger = CRIMINAL LUNATIC "


" Ironically, if one takes Phil's advice and searches
alt.guitar.amps for posts about flyback spikes, you find
him dodging the same basic question you asked about
generating 5 Kv spikes around 2/25/2003, for example. "

** No - it is 6 days earlier & cannot be in the
same thread as Arny is saying.


I specified no particular thread, Phil.


** You specified a date and a * particular * line of
content.


No, I specified a range of dates and a general line of
content.


** You specified a date

I said "around".


** A specific date was given.

That must refer to some post.



and claimed a * particular * line of content was there

No, general - you dodging an general question.


** That IS a particular * line of content * !!!!


- YOU DUMB SEPTIC ASSHOLE !!


You specified a date and claimed a * particular * line of content was
there - but not a shred of evidence to back up your ****wit assertion.

That is a worse DISHONESTY than from ANY of the audiophools you so like to
torment.



- but not a shred of
evidence to back up your ****wit assertion.

Never heard of google groups advanced search, I take it.


** There is NO SUCH THING to be found.

Go get totally ****ED !!

you MONSTROUSLY EVIL HYPOCRITE !




........ Phil

[Eeyore]

Patrick Turner wrote:

Eeyore wrote:
Patrick Turner wrote:
Eeyore wrote:
Patrick Turner wrote:
Ian Iveson wrote:
zyx wrote

I have an epi valve jr combo with 8" speaker that is 4 ohms. I want
to try it on a 12" speaker which is 8 ohms.

Jam away?

A bit risky. Anode voltage may rise higher than some parts can cope
with reliably.

As a general rule, SS amps don't care too much about a higher load
impedance, and valves are tolerant of a lower one.

SS amps have a load of NFB and there is a Zobel network which loads the
output, and there is no OPT, so no high voltages with no load, and supply
voltages are lower anyway,

Not to mention diodes fron output to supply rails too.

Graham

But I went on to say how inductive speaker loads on an SS amp could give
rise to destructive back emfs.

SS amps need all the protection they can get.

I don't think they're *inherently* any more fragile to be honest.

Graham

I am one of many technicians in my small city of 300,000 souls who
make a living repairing solid state crap.

Electronic products are NOT as rugged as they could or should be.

Patrick Turner.

I won't disagree with the general point. The reason being largely that they're
designed to a price.

Graham

[Eeyore]

Patrick Turner wrote:

Eeyore wrote:
Patrick Turner wrote:
Eeyore wrote:
Patrick Turner wrote:

What is NEVER fitted to an SS amp is an intelligent circuit that detects
if the load
is below 2 ohms and TURNS THE AMP OFF even if it is used at low level.
This safety option would save all the amps who expire when connected to
shorted speaker cables
or to fried/faulty speakers/crossovers.

Actually QSC have a very crude system that does do this.
http://www.freepatentsonline.com/4321554.html

What is the URL for the schematic?

http://patft.uspto.gov/netacgi/nph-P...&RS=PN/4321554

and click on images.

This does not work.

I went to the above site, and it asked me to click for a
plug in which failed to work.

If you give a URL of a schematic, please be SO KIND
to make completely sure that it is a ONE CLICK journey.

I'm not sure it's possible.

The link above was the US Patent Office site and it seems to use an Apple Quicktime plug-in to display images. If you'd had Quicktime installed it would have worked.

Why they feel that neccessary I do not know.

You may be able to get a copy of the patent from the previous link by creating a free account. I know I did get a pdf of it so it must be possible somehow.

Graham

[Eeyore]

Phil Allison wrote:

"Patrick Turner"

What is the URL for the schematic?
http://patft.uspto.gov/netacgi/nph-P...&RS=PN/4321554

and click on images.

This does not work.

** Forget it - it is all incomprehensible drivel anyhow.

Masses of brain numbing verbiage written in the usual pseudo-legal lingo of
a patent app.

BTW

I know the scheme as it is used in a few QSC power amplifiers - ie the USA
series.

And the MX, MXa and RMX series. The original Powerlights too IIRC.


Those amps completely * self destruct * if ever asked to drive a
saturating transformer load.

To be fair, that's not what they were designed to do.

Graham

[Eeyore]

Arny Krueger wrote:

"Phil Allison" wrote
"Arny Krueger "
"Phil Allison"

" Ironically, if one takes Phil's advice and searches
alt.guitar.amps for posts about flyback spikes, you find
him dodging the same basic question you asked about
generating 5 Kv spikes around 2/25/2003, for example. "

** No - it is 6 days earlier & cannot be in the
same thread as Arny is saying.


I specified no particular thread, Phil.


** You specified a date and a * particular * line of
content.


No, I specified a range of dates and a general line of
content.


** You specified a date

I said "around".

and claimed a * particular * line of content was there

No, general - you dodging an general question.

- but not a shred of
evidence to back up your ****wit assertion.

Never heard of google groups advanced search, I take it.

I found it easily enough with even needing the advanced search, but you'd given
me a timeline to search which made it easier.

Graham

[Eeyore]

Phil Allison wrote:

"Arny Krueger = CRIMINAL LUNATIC "

Never heard of google groups advanced search, I take it.

** There is NO SUCH THING to be found.

http://groups.google.com/advanced_search

You *CRIMINAL LIAR* Allison.

And wash your mouth with soap before posting here again.

Graham

[Eeyore]

flipper wrote:

"Arny Krueger" wrote:
"Patrick Turner" wrote in message
Eeyore wrote:
Patrick Turner wrote:
Eeyore wrote:
Patrick Turner wrote:

What is NEVER fitted to an SS amp is an intelligent
circuit that detects if the load
is below 2 ohms and TURNS THE AMP OFF even if it is
used at low level. This safety option would save all
the amps who expire when connected to shorted speaker
cables
or to fried/faulty speakers/crossovers.

Actually QSC have a very crude system that does do
this. http://www.freepatentsonline.com/4321554.html

What is the URL for the schematic?

http://patft.uspto.gov/netacgi/nph-P...&RS=PN/4321554

and click on images.

This does not work.

Works for me - perfectly!

I went to the above site, and it asked me to click for a
plug in which failed to work.

Update Quicktime on your computer.

In theory Quicktime might show them but I've never been able to get it
to work. They list a couple of 'free' plugins and I went though that
crap once but I guess a browser upgrade broke that too because the
images don't work for me anymore either.

Honestly, it works for me too.


Frankly, I think this place is a *lot* more convenient.

http://www.pat2pdf.org/

You put in the patent number you want then they retrieve it and
compile it into a nice PDF file for you.

Typical 'government' operation vs not only 'free enterprise' but just
plain FREE.

Nice one thanks.

Graham

[Eeyore]

flipper wrote:

Eeyore wrote:
flipper wrote:
"Arny Krueger" wrote:

Update Quicktime on your computer.

In theory Quicktime might show them but I've never been able to get it
to work. They list a couple of 'free' plugins and I went though that
crap once but I guess a browser upgrade broke that too because the
images don't work for me anymore either.

Honestly, it works for me too.

That's nice. Your headers also say you aren't using IE.

The headers here tell you absolutely nothing about what browsers I use.

Graham

[Phil Allison]

To be fair, that's not what they were designed to do.


** Shame about what the published data for the USA series actually says.

Shame how QSC sell a 70 volt line transformer to go with the USA series.

Not that an ASD ****ED pile of

CRIMINAL PSYCHOTIC POMMY ****

has ever read a single word of that.


FOAD Arsehole !!!




........ Phil

[Patrick Turner]

Phil Allison wrote:

"Patrick Turner"

Sensible SS guitar amps
have diodes from the output to
the rails to prevent swings on the output ever going more than the rail
voltage peak value,
since this can occur with the inductive load of a speaker, and cause
instant death to the output
bjts with reverse flow currents.

** Plenty of reliable BJT SS guitar and hi-fi amps have no such diodes.

( MOSFETS have such reverse diodes inherent inside the device.)

The need for "flyback diodes" only arises when the particular BJT amp
incorporates VI limiting circuitry to protect output devices from over
dissipation and SOA induced failures.

See: http://sound.westhost.com/vi.htm

....... Phil

Your article at the above address goes a long way twoards explaining the
pitfalls
of BJt and mosfet use and VI limiting.

Rod Elliot explains further.....

-------------------------------------------------------------------------------------------------------------------------------------
Some amplifier circuits show diodes connected between the output and the
+ve and -ve power rails - these are shown in grey in Figure 1. The
purpose of these
should now be obvious - they will "catch" the spikes generated under the
conditions Phil has explained. These will (hopefully) prevent the
destruction of output
transistors by shunting the excess voltage and current back into the
power supply which simply absorbs the energy. The diodes prevent the
amplifier's output
voltage from ever exceeding the supply by more than 0.65 volt or so, and
therefore prevent reverse biasing of the transistors under fault
conditions.

Needless to say, this provides zero sonic benefit, since the spikes will
still occur, but they will now be limited to a little over the
amplifier's supply voltage. The amp
will probably not self destruct, but it will sound just as horrible when
driven beyond its current limits.

High power amplifiers (i.e. anything over about 400W) nearly always use
MOSFETs rather than bipolar transistors, and this is especially true of
professional units
for sound reinforcement. There are very good reasons for this, as Phil
has explained.

The ability to drive virtually any load without the need for VI limiter
protection is one of the all time great advantages of power MOSFETs.
Naturally, the
requirement that there are sufficient output devices to handle the load
still exists, but MOSFETs are far more tolerant of fault conditions than
bipolar transistors, and
are not subject to a most undesirable problem known as "second
breakdown".

This occurs in bipolar transistors when a small section of the silicon
die becomes hotter than the rest due to an overload condition, or where
the devices are too
small for the job. This increases the gain in that small section, and
it therefore does even more of the work, causing it to get hotter
still. Thus a repeating the cycle is
started, which results in device destruction. This happens very fast
(in as little as a few tens of milliseconds), and it is virtually
impossible to protect the device once
second breakdown has started. The VI limiters are designed to prevent
the device(s) from ever exceeding the manufacturer limits where second
breakdown is
known to occur.

As Phil has shown, some attempts at achieving that goal are somewhat
less than a complete success.
-------------------------------------------------------------------------------------------------------------------------------------


My experience agrees generally with what Phil and Rod are saying.

I was taught early that having fuses in the rails and at the output
will prevent gross sudden current surges if the fuses are fast blow
types especially.

Mosfets have self limiting behaviour because they are transconductance
devices like tubes,
but will still produce huge currents, and if multiple mosfets are used
in an output stage it
it wise to have back to back external zeners of considerably less than
the 12V zeners fitted internally
to limit gate to source voltage, and hence maximum current flow via
drain to source.

I still place the diodes between output and rails anyway, even though it
may be argued that
these diodes to limit the output voltage ever swinging more than the
rails may not really be necessary.
I believe there is utterly no sonic penalty for these "clamping diodes".

Another failure mechanism in SS amps can be due to cross conduction
where
the pnp and npn devices fail to turn off quickly between each half of
the
wave form in class AB operation at F above say 10kHz.
When tested up to clipping level at say 30kHz, one sees that
inexplicably there is a huge
increase in rail supply current, even without a load.
Douglas Self alerted this problem to me when I first noticed this, but
his solution
to the phenomena problem wasn't completely as successful as I'd wish,
and I am still left wondering what could be done that would work better
than the Self method.
I have not noticed the same bother with mosfets, and not with vacuum
tubes of course.

Perhaps you may like to shed light on the phenomena of cross conduction.

Patrick Turner.

[Phil Allison]

"Patrick Turner"
Phil Allison wrote:


** Plenty of reliable BJT SS guitar and hi-fi amps have no such diodes.

( MOSFETS have such reverse diodes inherent inside the device.)

The need for "flyback diodes" only arises when the particular BJT amp
incorporates VI limiting circuitry to protect output devices from over
dissipation and SOA induced failures.

See: http://sound.westhost.com/vi.htm


Your article at the above address goes a long way twoards explaining the
pitfalls of BJt and mosfet use and VI limiting.


** Barely a beginner's primer - in fact.

Like most seemingly simple things - it soon gets all complicated when you
look right into it.

UK songwriter, Pete Townshend , said it all over 40 years ago.

In a little tune called "Substitute".

No allusions to BJTs intended.....



Rod Elliot explains further.....


** Well, he had to use his " editor's discretion " - didn't he ?.





....... Phil

[Patrick Turner]

Phil Allison wrote:

"Patrick Turner"

What is the URL for the schematic?

http://patft.uspto.gov/netacgi/nph-P...&RS=PN/4321554

and click on images.


This does not work.

** Forget it - it is all incomprehensible drivel anyhow.

Masses of brain numbing verbiage written in the usual pseudo-legal lingo of
a patent app.

BTW

I know the scheme as it is used in a few QSC power amplifiers - ie the USA
series.

Those amps completely * self destruct * if ever asked to drive a
saturating transformer load.

........ Phil

I built a pair of 50 watt class A amps with mosfet outputs
and an OPT.
When testing at full power below 10Hz, sure enough the core began to
saturate
and the mosfets were left to deal with the load being the dc resistance
of the
OPT primary, rather low, and the 0.22 ohm source resistor.
Attempts to blow the amp failed; perhaps had I used bjt they mau have
expired, and
probably anything would if run continuously with a saturated core.

In my OPTs I used C-cores with a max µ = 5,000 from around 1996 from
AEM.
At that time the µ of their cores wasn't very high for what was supposed
to be GOSS.

I found that placing a sheet of thin plastic sheet to make an "air" gap
using plastic shopping bag material reduced the µ to around 2,000, and
reduced the onset
of saturation so that the amp suffered by means of the falling amount of
load shunt reactance of the primary
inductance; ie, when the reactance = RL at 10Hz, the amp load has become
reactive,
and a value of 0.7 x RL, and although it then clipped sooner than when
at 1 kHz,
there were no saturation spikes in the wave form.

All about these mono amps is at
http://www.turneraudio.com.au/solids...no-mosfet.html

I doubt there would be any time when i would use a solid state or tube
amp
to drive into an external transformer, but transformers are used in all
ESL
so they sure can saturate, so some HPF at the input to limit input
below 10Hz would be advisable.

I have often thought that where one wants to use a pair of woofers or
midrange drivers
in a given speaker design then to avoid the low impedance of two
paralleled
6 ohm speakers becoming 3 ohms, and lower at the bass - mid crossover F,
or say 2 ohms at say 300Hz,
then a step down transformer to make the speaker of 1 ohm at the Xover
region ( there are
second order LPF and HPF at the same 300Hz, ) look like 4 ohms at least,
and the 3 ohms would appear as 12 ohms elsewhere across the band.

I have seen a pair of multi tap toroidals used for such Z transforming
functions,
a guy here bought a pair from a company in the US.
I placed them in sand filled boxes and fitted 4mm banana plug bind posts
for convenience
and tested the response which was from well below 3 Hz to about 1MHz,
and with low winding losses.
So if the transformers being used between an amp and speaker
is good quality, there is no audible extra distortion, and brilliantly
wide bandwidth,
and no need to worry about saturations.

Raising the effective speaker impedance with such a "matching
transformer"
usally does not cause any inconvenient loss of maximum power when maybe
only
5 watts is ever needed, and the amp is capable of 100 watts into 4 ohms
class AB.
If there is still 35 watts available for an average of 10 ohms, all is
well,
providing that any back emfs are not going to wreck the amp
if the speaker is not connected to the output of the matching tranny,
and someone turns up
the volume without knowing there isn't a speaker connected.
Thios sometimes happens when ppl forget to plug in the speakers, but
turn up the volume anyway,
before realizing there is a problem.

Patrick Turner.

[jh]

Eeyore schrieb:

Phread wrote:


"zyx" wrote in message

"zyx" wrote in message

I have an epi valve jr combo with 8" speaker that is 4 ohms. I want to try it on a 12" speaker which is 8 ohms.

Jam away?


Such mixed results.

who to believe... who to believe...

Dude!

Who to believe? Lord Valve is a musician who's been fixing guitar amps
for longer than you've been on the planet, most likely. Graham is a blow
hard know-it-all who responds to every question posted here even though
his actual knowledge of tube equipment is exactly zero.


Oh really ?

I'm a pro-audio designer with 35 yrs experience in the business and have plenty of knowledge of tube circuitry and I
even played a part in getting one tube guitar amp into volume production.


SNIP

Hí,
just curious,

which guitar amp?

thanks

Jochen

[Eeyore]

Phil Allison wrote:

To be fair, that's not what they were designed to do.

** Shame about what the published data for the USA series actually says.

Shame how QSC sell a 70 volt line transformer to go with the USA series.

That *saturates* in normal use ?

Graham

[Eeyore]

jh wrote:

Eeyore schrieb:

I'm a pro-audio designer with 35 yrs experience in the business and have plenty of knowledge of tube circuitry and
I even played a part in getting one tube guitar amp into volume production.

Hí,
just curious,

which guitar amp?

http://www.studiomaster.com/hp3.html

Graham

[Eeyore]

flipper wrote:

Eeyore wrote:
flipper wrote:
Eeyore wrote:

Honestly, it works for me too.

That's nice. Your headers also say you aren't using IE.

The headers here tell you absolutely nothing about what browsers I use.

I just knew you'd want to turn it into a completely useless
'argument'.

No, you started that by talking about my headers as if they told you anything
about the browsers I use.

I have 4 currently installed in fact including IE. I used to have 5.

Graham