Okay - here's definitely an UNUSUAL question... and I'm pretty sure that
nobody's ever messed with this stuff on such a scale... BUT I was reading
some of the web pages on the BBC Radiophonic Workshop about how they pulled
all the balancing transformers from alot of their equipment and were able to
get superior sonic results - it was in the spirit of this, and knowing that
alot of people like audio upgrades beef up power supplies to get greatly
increased clarity and dynamics - it kind of got me wondering about the
possibility of gutting the power supplies from some of my outboard equipment
and feed them directly with +24V or what-have-you from a master supply
located remotely. Has anybody heard of anyone experimenting with this???

I expect that doing so would achieve two things:
1. tighten up the clarity and dynamics (generally improve signal quality),
and
2. prevent interference from xformers in adjacent rack pieces. I've
certainly had problems with this and have had to rack stuff up to 5U apart
to avoid this.

Any Ideas??

Sincerely,
Jonathan

"Jonathan Dewdney" wrote
Any Ideas??

Your idea has it's merits.

The classic situation is a UPS which converts AC to DC then converts the DC
back to AC just so that the power supplies in our equipment can convert it
all back to DC. There must be a lot of extra noise and cost of components
in all that.

It would be a much better idea to have a single UPS which then distributed
DC at a couple of different voltages to all the equipment in the studio.

--
Anthony Gosnell

to reply remove nospam.

"Jonathan Dewdney" wrote in message

Okay - here's definitely an UNUSUAL question... and I'm pretty sure
that nobody's ever messed with this stuff on such a scale... BUT I
was reading some of the web pages on the BBC Radiophonic Workshop
about how they pulled all the balancing transformers from alot of
their equipment and were able to get superior sonic results - it was
in the spirit of this, and knowing that alot of people like audio
upgrades beef up power supplies to get greatly increased clarity and
dynamics - it kind of got me wondering about the possibility of
gutting the power supplies from some of my outboard equipment and
feed them directly with +24V or what-have-you from a master supply
located remotely. Has anybody heard of anyone experimenting with
this???

I expect that doing so would achieve two things:
1. tighten up the clarity and dynamics (generally improve signal
quality), and
2. prevent interference from xformers in adjacent rack pieces. I've
certainly had problems with this and have had to rack stuff up to 5U
apart to avoid this.

Any Ideas??

The classic way to increase isolation of individual circuits from a common
power supply is to distribute well-regulated DC at some higher voltage such
as 32 volts or higher, and use on-board regulators to bring it down to say,
24 volts.

In article ,
Jonathan Dewdney wrote:
Okay - here's definitely an UNUSUAL question... and I'm pretty sure that
nobody's ever messed with this stuff on such a scale... BUT I was reading
some of the web pages on the BBC Radiophonic Workshop about how they pulled
all the balancing transformers from alot of their equipment and were able to
get superior sonic results

Yes, bad input transformers can sound bad. Removing them can improve
things. However, some transformers sound really good and can solve a
lot of ground issues. So, I don't think it's an automatic win to get
rid of audio transformers.

it was in the spirit of this, and knowing that
alot of people like audio upgrades beef up power supplies to get greatly
increased clarity and dynamics - it kind of got me wondering about the
possibility of gutting the power supplies from some of my outboard equipment
and feed them directly with +24V or what-have-you from a master supply
located remotely. Has anybody heard of anyone experimenting with this???

One thing that using a shared power supply will do is make all of your
devices have a common ground through the power supply ground. This
might be a good thing, but it might also be bad.

Normally, if a device has a power transformer, the power supply ground
is created inside of the power supply circuit and can be connected to
the grounds associated with the audio IOs by the designer of that
piece of gear, and that piece only.

With a shared power supply, you get a shared ground, so the
relationship between gear is in many ways more complicated than if
power transformers are used. Maybe it won't cause problems, but there
will definitely be a more complex and interconnected ground scheme
when a shared supply is used.

I expect that doing so would achieve two things:
1. tighten up the clarity and dynamics (generally improve signal quality),

A larger and more complex ground system wouldn't automatically make
the think that you'd go in that direction at all. Actually, I'd
expect more of the opposite. With a more complex and interconnected
ground, I would think that crosstalk and the like would be worse.
Also, with a shared DC supply, any variation on power suppy rails
would be shared among several devices, and that should work to
increase the interaction of devices with each other and probably
reduce clarity.

and
2. prevent interference from xformers in adjacent rack pieces. I've
certainly had problems with this and have had to rack stuff up to 5U apart
to avoid this.

Toroidal transformers would be a better idea IMHO. They have very low
radiated fields, and you can put them in a box to reduce fields
further.

Any Ideas??

If you try something like this, also consider what happens when a
device fails and draws a lot of current. When you combine supplies
for several pieces of gear into one large supply, a fault situation
might not be high enough to trip the larger supply with its high
combined current rating.

Old large computers built in this way used to have smoke detectors
installed at the top of each rack to detect this fault situation. A
better way might be to use local regulation, but you still have a
problem if a regulator fails and starts to hammer the main supply.


Best of luck,

Monte McGuire

Jonathan Dewdney wrote:
Okay - here's definitely an UNUSUAL question... and I'm pretty sure that
nobody's ever messed with this stuff on such a scale... BUT I was reading
some of the web pages on the BBC Radiophonic Workshop about how they pulled
all the balancing transformers from alot of their equipment and were able to
get superior sonic results - it was in the spirit of this, and knowing that
alot of people like audio upgrades beef up power supplies to get greatly
increased clarity and dynamics -

Removing audio transformers was very popular in the seventies. I think
in general it's a good idea, but others will disagree. I am not a fan of
audio transformers in the signal path if it can be avoided.

it kind of got me wondering about the
possibility of gutting the power supplies from some of my outboard equipment
and feed them directly with +24V or what-have-you from a master supply
located remotely. Has anybody heard of anyone experimenting with this???

This, however, is mostly a silly idea. What good is removing the power supply
going to do you?

I expect that doing so would achieve two things:
1. tighten up the clarity and dynamics (generally improve signal quality),

Why will it do this?

and
2. prevent interference from xformers in adjacent rack pieces. I've
certainly had problems with this and have had to rack stuff up to 5U apart
to avoid this.

This will definitely be the case... BUT now you will have a huge honking
power supply at the bottom of your rack. You aren't eliminating the problem,
just moving it.

You'd probably gain more just by replacing crappy transformers in low end
gear with low-magnetic-leakage types.
--scott

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

In article writes:

I was reading
some of the web pages on the BBC Radiophonic Workshop about how they pulled
all the balancing transformers from alot of their equipment and were able to
get superior sonic results - it was in the spirit of this, and knowing that
alot of people like audio upgrades beef up power supplies to get greatly
increased clarity and dynamics - it kind of got me wondering about the
possibility of gutting the power supplies from some of my outboard equipment
and feed them directly with +24V or what-have-you from a master supply
located remotely.

There are two different things. "Balancing transformers" are signal
input and output transformers (see thousands of "transformer vs.
transformerless" discussions).

Power supplies are power supplies and some of them are pretty sleazy.
Removing signal transformers will definitely change the sound of your
equipment - for better or worse depends on how good the transformers
are, what the equipment is connected to, and whether you like the
sound of transformers or not. Making a more solid power supply can
sometimes improve the sound, but not always. It depends on whether
there's a design problem with the original power supply, and it also
depends on how voltages are distributed within the piece of gear.

In other words, there's no general answer. There are some transformers
that are known to be dogs and removing them benefits nearly everyone.
There are some power supplies that are known dogs and replacing them
benefits neearly everyone. Anything in between and you're just
experimenting. It could prove fruitful, or maybe not. Do what you can
afford, but don't make any big investments that you'll regret because
you didn't get any benefit from them.

2. prevent interference from xformers in adjacent rack pieces. I've
certainly had problems with this and have had to rack stuff up to 5U apart
to avoid this.

That's kind of extreme, but I have indeed heard of (and even
experienced) induced hum from adjacent rack mount units. One of the
few benefits of wall warts is that you can move the transformer to a
safe place, but you have to be aware of the magnetic field in that
area and keep cables away from it.

However a bigger rack is almost always cheaper than a bunch of new
power supplies.


--
I'm really Mike Rivers - )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

Here is a solution I am using for powering some mic pres I am
designing... It is a remote PS unit that will provide +- 15VDC, +- 24
VDC and +48VDC. All from high capacity linear supplies.

The +-15 supplies are for monolithic pres and the +-24 is for 990C
base pres. I haven't added the +-24 supply yet but there is a bay for
it inside and holes for multi pin XLR's on the back once I get going
on the 990C preamps.

The pres I build for other people have integral supply boards with
external transformers.

Here are some picture links:

http://www.mixposse.com/attach/Pre_P...pply_Front.jpg

http://www.mixposse.com/attach/Pre_PowerSupply_Rear.jpg

The remote supply really keeps low level hum down to a minimum.

Jonathan Dewdney wrote:
Okay - here's definitely an UNUSUAL question... snip

Hi Jonathan,

Not all that unusual, in fact, Rane tried exactly that setup with their
gear several years ago, calling the system "Remote AC Power" or RAP, not
to be confused with this newsgroup or the musical styleG!

It didn't seem to take off in the marketplace, for whatever reason.
There used to be a great application note describing the system in their
library... but it doesn't appear to be there at the moment. There is an
article that talks about the history:

http://www.rane.com/pdf/note133.pdf

And if you email their support desk I'll bet they'll find you a copy of
the original if one still exists. They are pretty good like that.

OK, I've experimented with this sort of thing a lot, mostly looking to
eliminate transformer mechanical hum, ground loops, radiated noise, etc.
I have a couple of thoughts...

My first attempt was a single transformer feeding several devices. Each
device was modified so that I could apply the appropriate voltage to the
input of the local bridge.

Sadly, since some of the gear has unbalanced I/O I ended up creating a
loverly ground loop... next.

The next attempt was a bunch of smaller transformers located remotely
feeding the same gear. It actually worked quite nicely, but just lacked
a certain elegance.

While I knew up front it was going to be a nightmare, I tried
distributing DC as well. As was expected, the groundloop problem was
pretty bad.

Well, now, what the heck! Everything is going back to a common ground,
and even though there are loops, I really shouldn't be having such a
problem. What to do?

Well, it might sound a bit wierd, but I basically built a differential
low voltage distribution network, carefully groomed the ground paths,
and voila... a workable solution. In fact a very good solution. Except
that it will be a LOT of work to implement. Still, I am considering it
for the next version of the studio...

If you take this approach, you will need to pay careful attention to the
paths to ground. The first step is probably to make sure that all "pin
1" type problems are addressed. Since I use a single pair for both
balanced and unbalanced gear this turned out to be reasonable. I also
made sure that EVERY piece used three conductors for power - hot,
neutral, and safety ground. AND, all audio grounds are home runs to a
central ground located in the patchbay racks, and all power grounds are
home runs to the ground at the transformer, which is located at the
service entrance.

Pros: All the benefits of low voltage distribution, all the benefits of
differnetial distribution, enforced star groundingG

Cons: A lot of work to implement, all the gear has to be modified.

Certainly was an interesting experiment though.

Thanks all for your input. It's just an idea I was flitting about in my
head. I use alot of naim playback gear - they're bullish on supplies... and
offer upgrades via beefier power supplies. Seems to hold true from what I'd
heard with my own ears. At any rate, it struck me as downright weird that
tape decks had power supplies located in them and that the EM might be
consequential to such a machine. I removed the P/S from my A810 to a remote
enclosure and what it did to the sound quality was nothing short of amazing!
SO I tried the same thing with a Yamaha REV5. Same. Unless I'm just hearing
things with my delusions. This also relates to my SSL power supply I'm
selling (see other post, same date) - which would be the means to do
something like this - though I think I secretly don't want to (why I'm
selling the thing)... but I thought I'd get some opinions before I actually
did.

The only big problem is that I'd have to start reverse-engineering every
piece of gear I have. But maybe that's what college students are for (think
EE dept..! exploitation....).

At any rate, I want to respond to the individuals who already responded
here...

1. Monte, good points. I think Bill clarified how the ground issues might be
solved. And yes, I AM using a toroid for my one experimental supply. 200VA
with two votage rails. The failure issue is a good one. And one I need to
consider.

2. Scott! Thanks for your input. You'd be surprised at what a little more
juice will do for headroom! I promise you. The rack would be located at
least eight feet away. And yes! the idea WOULD be to move the problem. More
juice and (literally) move the problem away! I expect I would see MORE
benefit from my lower-end gear... since the one design feature that tends to
distinguish low end from high end is the power supply. But like I said - I'm
just kind of thinking out loud here - not prosetylizing.

3. Mike... Sorry I shouldn't have brought up both issues at once perhaps.
The two are quite separate in my head and so they should be in yours. Sorry
to make you think I was confusing them. Balancing transformers are just that
and power transformers have nothing to do with them. I'm not even thinking
of induced hum. Think about it. You have a complex LCR or even digital
network in a piece of rack gear. All the voltage drops are carefully
calculated by the designers. Then you immerse this whole damn thing in a
pool of 60Hz magnetic fields, all located in varying positions around it. Do
you think this thing is operating within spec? At ALL?? Really... think
about it. Isn't it kind of amazing that the gear works at all? I first got
clued into the whole notion (as an interesting or not so interesting
sidebar) in the 80s when I was trying to play guitar through a Midiverb
which was sitting atop a guitar amp. It started making this CRAZY honking
sound until I placed the unit several feet away.

4. Bill... thanks for the ideas. And for being encouraging. I'd really like
to pick your brain about this further.

sincerely,
JW Dewdney




in article , Bill Thompson at
wrote on 3/2/04 12:22:

Jonathan Dewdney wrote:
Okay - here's definitely an UNUSUAL question... snip

Hi Jonathan,

Not all that unusual, in fact, Rane tried exactly that setup with their
gear several years ago, calling the system "Remote AC Power" or RAP, not
to be confused with this newsgroup or the musical styleG!

It didn't seem to take off in the marketplace, for whatever reason.
There used to be a great application note describing the system in their
library... but it doesn't appear to be there at the moment. There is an
article that talks about the history:

http://www.rane.com/pdf/note133.pdf

And if you email their support desk I'll bet they'll find you a copy of
the original if one still exists. They are pretty good like that.

OK, I've experimented with this sort of thing a lot, mostly looking to
eliminate transformer mechanical hum, ground loops, radiated noise, etc.
I have a couple of thoughts...

My first attempt was a single transformer feeding several devices. Each
device was modified so that I could apply the appropriate voltage to the
input of the local bridge.

Sadly, since some of the gear has unbalanced I/O I ended up creating a
loverly ground loop... next.

The next attempt was a bunch of smaller transformers located remotely
feeding the same gear. It actually worked quite nicely, but just lacked
a certain elegance.

While I knew up front it was going to be a nightmare, I tried
distributing DC as well. As was expected, the groundloop problem was
pretty bad.

Well, now, what the heck! Everything is going back to a common ground,
and even though there are loops, I really shouldn't be having such a
problem. What to do?

Well, it might sound a bit wierd, but I basically built a differential
low voltage distribution network, carefully groomed the ground paths,
and voila... a workable solution. In fact a very good solution. Except
that it will be a LOT of work to implement. Still, I am considering it
for the next version of the studio...

If you take this approach, you will need to pay careful attention to the
paths to ground. The first step is probably to make sure that all "pin
1" type problems are addressed. Since I use a single pair for both
balanced and unbalanced gear this turned out to be reasonable. I also
made sure that EVERY piece used three conductors for power - hot,
neutral, and safety ground. AND, all audio grounds are home runs to a
central ground located in the patchbay racks, and all power grounds are
home runs to the ground at the transformer, which is located at the
service entrance.

Pros: All the benefits of low voltage distribution, all the benefits of
differnetial distribution, enforced star groundingG

Cons: A lot of work to implement, all the gear has to be modified.

Certainly was an interesting experiment though.

Bill Thompson wrote in message ...
--snip--
....Rane tried exactly that setup with their gear several years ago...

....I also made sure that EVERY piece used three conductors for power -
hot,
neutral, and safety ground.
---snip---


Just to be picky, if your power cord has a black wire, a white wire,
and a green wire, the white wire isn't the neutral, it's the grounded
conductor (connected to ground at the service entrance and insulated
from ground everywhere downstream of that) and carries the exact same
current as the black wire, and the green wire is the grounding
conductor and carries no current unless something goes wrong. If you
have a black wire, a red wire, and a white wire then the black and the
red are the "hot" wires and the white is the neutral, although it is
still not supposed to be connected to ground anywhere except all the
way back at the service entrance.
Is that Rane thing the one where they use an oversize wallwart and an
RJ-45 plug?

In rec.audio.pro, (Monte P McGuire) wrote:

In article ,
Jonathan Dewdney wrote:

...

it was in the spirit of this, and knowing that
alot of people like audio upgrades beef up power supplies to get greatly
increased clarity and dynamics - it kind of got me wondering about the
possibility of gutting the power supplies from some of my outboard equipment
and feed them directly with +24V or what-have-you from a master supply
located remotely. Has anybody heard of anyone experimenting with this???

One thing that using a shared power supply will do is make all of your
devices have a common ground through the power supply ground. This
might be a good thing, but it might also be bad.

One feature of well-designed equipment is that the ground
connections of the input and output connectors are carefully chosen
inside the unit so if there is significant leakage current through
ground, it doesn't show up in the signal path. Bill Whitlock of Jensen
Transformers has written some excellent articles on this and related
causes of hum and noise (so much so that you can probably solve all
your hum/ground loop problems without using any audio transformers!),
and I urge anyone who wants to add, change or rearrange, or is having
problems with ground connections to read his articles.
Go to http://www.jensen-transformers.com/ and click on 'white papers'
and read the articles on that page.
Of course, there's a lot of equipment that's not designed well as
far as internal ground connections, so connecting to this main DC
power supply ground might actually increase their ground-loop hum
immunuty.
I recall that Mr. Whitlock proposed a test where 60 Hz current
injected through an input or output's 'pin 1' ground connection and
another ground on the same piece of equipment, and the 'signal'
generated is measured on the output. This is an excellent test for
immunity to ground loop problems.

Normally, if a device has a power transformer, the power supply ground
is created inside of the power supply circuit and can be connected to
the grounds associated with the audio IOs by the designer of that
piece of gear, and that piece only.

With a shared power supply, you get a shared ground, so the
relationship between gear is in many ways more complicated than if
power transformers are used. Maybe it won't cause problems, but there
will definitely be a more complex and interconnected ground scheme
when a shared supply is used.

I expect that doing so would achieve two things:
1. tighten up the clarity and dynamics (generally improve signal quality),

I think a better solution would be to beef up the power supply (and
perhaps other things such as ground connections) in each piece of
equipment. Things that can be done:
Put 0.1 uF caps (at appropriate voltage rating) directly (using as
short leads as possible) across each rectifier. I also like to put
0.1's across the AC input (transformer secondary) and DC output, just
for overkill. This keeps several posssible RF interference problems
from happening. These can go on the inputs and outputs of voltage
regulators as well, but there's the possibility of capacitive loading
making regulators unstable, so be careful with that (read data sheets,
app notes, and books such as Pease's "Trobleshoorting Analog
Circuits").
Replace the main filter cap(s) with larger value. Problems with
this are that if you have a 'stiff' transformer (one that can provide
a lot of current - wall-warts generally can't), you may need to
replace the rectifiers with ones with greater peak current capability.
Also, since the peak current will be greater and the conduction angle
of the rectifier charging the cap will be lower, this pulls a more
non-linear current waveform with even more harmonic content from the
power line, which may be picked up by not-well-designed, er, uh,
'sensitive' equipment.

A larger and more complex ground system wouldn't automatically make
the think that you'd go in that direction at all. Actually, I'd
expect more of the opposite. With a more complex and interconnected
ground, I would think that crosstalk and the like would be worse.
Also, with a shared DC supply, any variation on power suppy rails
would be shared among several devices, and that should work to
increase the interaction of devices with each other and probably
reduce clarity.

and
2. prevent interference from xformers in adjacent rack pieces. I've
certainly had problems with this and have had to rack stuff up to 5U apart
to avoid this.

Toroidal transformers would be a better idea IMHO. They have very low
radiated fields, and you can put them in a box to reduce fields
further.

Any Ideas??

If you try something like this, also consider what happens when a
device fails and draws a lot of current. When you combine supplies
for several pieces of gear into one large supply, a fault situation
might not be high enough to trip the larger supply with its high
combined current rating.

The solution would be to have an appropriate fuse at the power
input of each device. One problem with this is it raises the impedance
of the power supply as seen by each device.

Old large computers built in this way used to have smoke detectors
installed at the top of each rack to detect this fault situation. A
better way might be to use local regulation, but you still have a
problem if a regulator fails and starts to hammer the main supply.

A fuse between the main supply and each local regulator would work
fine here, as the impedance the final circuit sees is that of the
local regulator.



Best of luck,

Monte McGuire


-----
http://mindspring.com/~benbradley

unitron wrote:

Just to be picky, if your power cord has a black wire, a white wire,
and a green wire, the white wire isn't the neutral, it's the grounded
conductor

Wow... I didn't know that. I've always heard it described as the neutral

(connected to ground at the service entrance and insulated
from ground everywhere downstream of that) and carries the exact same
current as the black wire,

although that is my understanding of how "neutral" is connected, and how
it works.

and the green wire is the grounding conductor and carries no current unless something goes wrong.

agreed.

If you have a black wire, a red wire, and a white wire then the black and the
red are the "hot" wires and the white is the neutral, although it is
still not supposed to be connected to ground anywhere except all the
way back at the service entrance.

also agreed... though I know a lot of folks use red in "three-way"
switching arrangements as the line that might be hotG!

Is that Rane thing the one where they use an oversize wallwart and an
RJ-45 plug?

That's the one!

Thanks for the info on house wiring...

Bill

Bill Thompson wrote:
unitron wrote:

Just to be picky, if your power cord has a black wire, a white wire,
and a green wire, the white wire isn't the neutral, it's the grounded
conductor

Wow... I didn't know that. I've always heard it described as the neutral

(connected to ground at the service entrance and insulated
from ground everywhere downstream of that) and carries the exact same
current as the black wire,

although that is my understanding of how "neutral" is connected, and how
it works.

Right. The white wire is the neutral. In a typical installation, it is
bonded to the ground at the point where the building ground enters the
system, which is normally the service entry panel. It's being used as
the current return, not the green wire. But this is the terminology
that electricians use, and that you will find in the NEC book.

The thing is that this terminology is different than the terminology that
electronics guys use... Electronics guys will talk about the ground being
the current return, and the safety ground ("Chassis ground") being a different
thing.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

In article writes:

unitron wrote:

Just to be picky, if your power cord has a black wire, a white wire,
and a green wire, the white wire isn't the neutral, it's the grounded
conductor

Wow... I didn't know that. I've always heard it described as the neutral

Don't let him kid you. An electrician will tell you that it's the
neutral wire, and that the green wire is the safety ground wire. It's
correct that the neutral wire is supposed to be connected to ground at
one point only. That's why it's called "neutral" rather than "ground."


--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

(Mike Rivers) wrote in message news:znr1078350305k@trad...
In article writes:

unitron wrote:

Just to be picky, if your power cord has a black wire, a white wire,
and a green wire, the white wire isn't the neutral, it's the grounded
conductor

Wow... I didn't know that. I've always heard it described as the neutral

Don't let him kid you. An electrician will tell you that it's the
neutral wire, and that the green wire is the safety ground wire. It's
correct that the neutral wire is supposed to be connected to ground at
one point only. That's why it's called "neutral" rather than "ground."

My source is the National Electrical Code. Electricians don't
always use the official approved terminology but they know that
touching the bare part of the white wire while standing barefoot in a
puddle is not the same as touching the bare part of the green wire
under the same circumstances. Hey, I said I was being picky.

A single phase 3 wire 240 Volt circuit has 2 "hots" and a neutral
and theoretically no current flows in the neutral. (think center
tapped transformer feeding bipolar supply for op-amps; supposedly the
loads, and current flow, will be the same-just in opposite directions-
on both the + and the - sides of the supply so that the voltage
differential, i.e., difference in potential, between the point where
the loads meet and the "grounded" center tap will be zero. Just as
equal but oppositely charged protons and electrons combined are
chargeless neutrons, the 2 current flows of equal but opposite
polarity-one peaking positively when the other peaks negatively-cancel
each other out where they meet.) Of course in real life no split load
will have exactly the same impedance in both halves, so one or more
electrons will return through the neutral, but in many cases it is
permissible to use a smaller gauge of wire for the neutral than the
two hots because the current in the neutral will be less than the
current in either hot due to the opposite polarity current in the
other hot.

A single phase 3 wire 120 Volt circuit has a white wire that carries
the same current that passes along the black wire. It would do so
even if not connected to ground as long as connected to the other
terminal of the current source to which the black wire is connected.
It is grounded at the service entrance (the meter) for safety, not for
electrical efficiency. It also may not be interrupted at any point by
a switch or fuse or circuit breaker, unless said interuption is part
of a multi-pole device that simultaneously breaks the circuit on the
hot wire side as well. The NEC also refers to the white wire as the
identified wire whether serving as a neutral or not.

The green wire is also grounded at the service entrance but is
referred to as the grounding (not grounded) conductor since it is not
part of the circuit and exists only to provide grounding in the event
of something going wrong, such as the hot wire breaking off and
contacting a case or chassis, at which point it is supposed to shunt
the majority of the current to ground rather than allowing it to flow
through someone or something else in contact with the case or chassis.
It too may not be interrupted except with the kind of aforementioned
multi-pole device.

Speaking of neutral wires, I'm thinking of starting up a new thread of
the bi-wiring off of a single amp discussion, this time centered on
whether one could do so with 3 wires instead of 4, one hot for the
woofer, one for the tweeter, and a common return. Whadda ya think?
:-)

unitron wrote:

Speaking of neutral wires, I'm thinking of starting up a new thread of
the bi-wiring off of a single amp discussion, this time centered on
whether one could do so with 3 wires instead of 4, one hot for the
woofer, one for the tweeter, and a common return. Whadda ya think?
:-)

Should work, provided:

1) the amps are ground-referenced on the low side not bridged.
2) you're aware of the potentially higher current flow in the common wire.

This would surely only give half of the biwiring advantage, which is
questionable to start with...

--
Mark.
http://tranchant.plus.com/

On 4 Mar 2004 07:20:29 -0800, (unitron) wrote:

Just as
equal but oppositely charged protons and electrons combined are
chargeless neutrons,

You probably meant this poetically, but it's not *literally* true.
Don't you just hate nitpickers? Me too.

Chris Hornbeck

"Second star to the right,
Then straight on 'til morning."

unitron wrote:
A single phase 3 wire 240 Volt circuit has 2 "hots" and a neutral and
theoretically no current flows in the neutral.

Where I am, the Netherlands, such a circuit has one 'hot' wire (phase), one
'null' wire (neutral) and one 'earth' wire (ground). Current only flows
when something conductive between phase and neutral is connected, so you
can't claim these are *both* hot wires. When I measure between phase and
neutral I see 230 V; between phase and ground also 230 V; between neutral
and ground there's 0 V, i.e.: one hot wire.

Obviously I can't comment on colors used where you are (overhere phase is
brown, neutral is blue and ground is green/yellow), but maybe some more can
be added about the term 'neutral'. It is called that because in the way
power is generated - commonly in a rotary/ 3-phase manner - the point where
the three phases share their common connection is the neutral point, or
null. Therefor this is not a second 'hot' and neither the same as 'ground'
(unless one wants it to be, and connects it to ground). Now aviation,
that's where life is simple: there's only 'hot' or 'plus', and the rest is
all the same; neutral, minus, ground, safety ground, chassis ground, static
ground, lightning conductor, aircraft frame, sigh.. No earth though :-)

Luck, Arjan

--
----Real email: news then at then soundbyte then dot then nl----

Arjan P wrote:
unitron wrote:
A single phase 3 wire 240 Volt circuit has 2 "hots" and a neutral and
theoretically no current flows in the neutral.

Where I am, the Netherlands, such a circuit has one 'hot' wire (phase), one
'null' wire (neutral) and one 'earth' wire (ground). Current only flows
when something conductive between phase and neutral is connected, so you
can't claim these are *both* hot wires. When I measure between phase and
neutral I see 230 V; between phase and ground also 230 V; between neutral
and ground there's 0 V, i.e.: one hot wire.

That is how a 120 volt circuit in the US works. The US 240V three-wire
connections come off of a transformer with a center tap on it, and the
center tap is bonded to ground. (This is basically "balanced power.")
It's the same way that 460V circuits in Europe work.

Obviously I can't comment on colors used where you are (overhere phase is
brown, neutral is blue and ground is green/yellow), but maybe some more can
be added about the term 'neutral'. It is called that because in the way
power is generated - commonly in a rotary/ 3-phase manner - the point where
the three phases share their common connection is the neutral point, or
null. Therefor this is not a second 'hot' and neither the same as 'ground'
(unless one wants it to be, and connects it to ground). Now aviation,
that's where life is simple: there's only 'hot' or 'plus', and the rest is
all the same; neutral, minus, ground, safety ground, chassis ground, static
ground, lightning conductor, aircraft frame, sigh.. No earth though :-)

Ground return through aircraft frame is BAD! BAD BAD! Yeah, I know cars
do it...
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

In article unitron wrote:
: (Mike Rivers) wrote in message news:znr1078350305k@trad...
:
: Don't let him kid you. An electrician will tell you that it's the
: neutral wire, and that the green wire is the safety ground wire. It's
: correct that the neutral wire is supposed to be connected to ground at
: one point only. That's why it's called "neutral" rather than "ground."

: My source is the National Electrical Code. Electricians don't
: always use the official approved terminology but they know that
: touching the bare part of the white wire ..

delurks

reaches over for his copy of the NEC

sound of pages riffling

He's right, Mike. Picky, but right.

But I've also talked many times to master electricians who
call it the "neutral". And personally, I think the subtle linguistic difference
between a "grounded conductor" and a "grounding conductor" for wires with
two completely different purposes is the real reason why most electricians I
know say "neutral". Except for the wire-size rule differences between the correct
"neutral" the colloquially-named "neutral", the um, "wire that carries the return or
unbalanced current to ground in normal energized operation" has generally the same
code requirements and safety hazards for both cases.

relurks

Bob (old fart) Miller
remove spammenot to reply

Scott Dorsey wrote:
That is how a 120 volt circuit in the US works. The US 240V three-wire
connections come off of a transformer with a center tap on it, and the
center tap is bonded to ground. (This is basically "balanced power.")
It's the same way that 460V circuits in Europe work.

Mmh, I'm not aware of those circuits at all, could be my ignorance but as
far as far as I know there's either single phase 230V or 3-phase 400V.
Which is the effective voltage between two phases of 230V with a 120 degree
phase shift. Interesting, with the center tap.

Ground return through aircraft frame is BAD! BAD BAD! Yeah, I know cars
do it...

Huh? Maybe you're talking about composite aircraft, but airframe ground
return is all there is on today's aircraft, since it cuts the amount of
cable = weight in half (outside the studio I'm an avionics engineer). The
only exceptions to it are antenna and pickup wiring and data lines
obviously. On the newest Airbus designs they're even considering increasing
main power for certain systems from 115V/400Hz to a higher level to further
decrease cable weight.

Luck, Arjan

--
----Real email: news then at then soundbyte then dot then nl----

Jonathan Dewdney wrote:

Okay - here's definitely an UNUSUAL question... and I'm pretty sure that
nobody's ever messed with this stuff on such a scale... BUT I was reading
some of the web pages on the BBC Radiophonic Workshop about how they pulled
all the balancing transformers from alot of their equipment and were able to
get superior sonic results

Yes - audio transformers aren't the smartest things to have in the signal path.

- it was in the spirit of this, and knowing that
alot of people like audio upgrades beef up power supplies to get greatly
increased clarity and dynamics

Clarity ? You might get better dynamics in a power amp by upgrading the PSU but
that's another issue.

- it kind of got me wondering about the
possibility of gutting the power supplies from some of my outboard equipment
and feed them directly with +24V

Most decent gear needs 'split rail' supplies, i.e. + and - Volts and rarely
24V.

or what-have-you from a master supply
located remotely. Has anybody heard of anyone experimenting with this???

No, never.

I expect that doing so would achieve two things:
1. tighten up the clarity and dynamics (generally improve signal quality),

How ? You've been listening to the audiophile crowd who think 'one way' cables
are cool too ?

and
2. prevent interference from xformers in adjacent rack pieces. I've
certainly had problems with this and have had to rack stuff up to 5U apart
to avoid this.

Bad equipment design then. Replace the cheap transformers with qualty toroids
might be a good idea.

Any Ideas??

Don't do what you just suggested.

Graham

Arny Krueger wrote:

The classic way to increase isolation of individual circuits from a common
power supply is to distribute well-regulated DC at some higher voltage such
as 32 volts or higher, and use on-board regulators to bring it down to say,
24 volts.

This is fine for telecoms. As in telephone quality.

Don't even get me started about ground return currents and the problems that
will add.

Graham

Arjan P wrote:

Huh? Maybe you're talking about composite aircraft, but airframe ground
return is all there is on today's aircraft, since it cuts the amount of
cable = weight in half (outside the studio I'm an avionics engineer). The
only exceptions to it are antenna and pickup wiring and data lines
obviously. On the newest Airbus designs they're even considering increasing
main power for certain systems from 115V/400Hz to a higher level to further
decrease cable weight.

Don't you have 400 Hz eddy currents everywhere, and 400 Hz trash leaking
into everything? My experience with aircraft stuff is mostly military
craft, which are a soup of 400 Hz in spite of careful grounding and sometimes
even shielded power lines.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

"Scott Dorsey" wrote in message

Arjan P wrote:

Huh? Maybe you're talking about composite aircraft, but airframe
ground return is all there is on today's aircraft, since it cuts the
amount of cable = weight in half (outside the studio I'm an avionics
engineer). The only exceptions to it are antenna and pickup wiring
and data lines obviously. On the newest Airbus designs they're even
considering increasing main power for certain systems from
115V/400Hz to a higher level to further decrease cable weight.

Don't you have 400 Hz eddy currents everywhere, and 400 Hz trash
leaking into everything? My experience with aircraft stuff is mostly
military craft, which are a soup of 400 Hz in spite of careful
grounding and sometimes even shielded power lines.

Agreed. The Hawk ca- 60s CW RADARs I worked with involved listening to
Doppler tones in the audible range. I don't know how they picked the
frequency of the RF. Perhaps conincidentally the RF carrier frequency chosen
put all of the audio signals that were interesting well above 2400 Hz.
Those days were still mostly about tubes and selenium rectifiers, though
just a little germanium and silicon was creeping in.

All you have to do is look at the Fletcher-Munson curves and compare
audibility of 60 Hz to 400 Hz on say the 30 dB curve (something like 30 dB
difference) , or 360 Hz versus 2400 Hz ( about 10 dB difference). OTOH, a
line frequency of 1200 Hz or higher happily starts one back up the
audibility curve for 3 phase full wave rectification.

In the old days the most problematic aspect of 400 Hz was building
synchronous motors that spun slow enough to do useful things without lots of
gearing. Today, they would probably be DC servos.

I don't think that power transmission losses are much of an issue below 10
KHz and lengths under 500'. Above 10 KHz self-inductance and skin effect
start rearing their ugly heads, when losses have to be REALLY low and
currents are high.

Scott Dorsey wrote:
Huh? Maybe you're talking about composite aircraft, but airframe
ground return is all there is on today's aircraft, since it cuts the
amount of cable = weight in half (outside the studio I'm an avionics
engineer). The only exceptions to it are antenna and pickup wiring and
data lines obviously. On the newest Airbus designs they're even
considering increasing main power for certain systems from 115V/400Hz
to a higher level to further decrease cable weight.

Don't you have 400 Hz eddy currents everywhere, and 400 Hz trash leaking
into everything? My experience with aircraft stuff is mostly military
craft, which are a soup of 400 Hz in spite of careful grounding and
sometimes even shielded power lines.

Yes, there's a lot more to it then saying 'all grounds are the same', and
shielding equipment and certain wiring is essential. As is the electrical
bonding of all structural elements to make sure return currents do flow in
the shortest route (and static buildup gets discharged where the designers
want it to go - from replaceable dischargers and not wingtips or flight
control surfaces). A number that comes to mind for, say bonding of an
elevator surface, to the reference (AC ground connection, usually aircraft
nose) is 20 milliOhms.

Most of the potential problems are being tackled in the design stage
though; return paths are calculated and AC systems never share the same
grounding location (to the airframe) with DC systems, and the same goes for
shielding grounds. Not to mention the cable separations in different cable
looms for different types of signals and systems and then also splitting
different identical main systems from each other and their backups; this
also for redundancy reasons. I think it's safe to say that here the
difference between cars and aircraft become apparent, to say the least..
And then, the smaller the aircraft - the bigger the problems, since
everything has to get crammed into the same tight space. Mmh, getting quite
off topic, this one..

Luck, Arjan

--
----Real email: news then at then soundbyte then dot then nl----

(Mike Rivers) wrote in message news:znr1078350305k@trad...
In article writes:

unitron wrote:

Just to be picky, if your power cord has a black wire, a white wire,
and a green wire, the white wire isn't the neutral, it's the grounded
conductor

Wow... I didn't know that. I've always heard it described as the neutral

Don't let him kid you. An electrician will tell you that it's the
neutral wire, and that the green wire is the safety ground wire. It's
correct that the neutral wire is supposed to be connected to ground at
one point only. That's why it's called "neutral" rather than "ground."

Right, also that it connects to the center tap on the utility
transformer and provides the reference for 120V circuits.

Mark Tranchant wrote in message ...
unitron wrote:

Speaking of neutral wires, I'm thinking of starting up a new thread of
the bi-wiring off of a single amp discussion, this time centered on
whether one could do so with 3 wires instead of 4, one hot for the
woofer, one for the tweeter, and a common return. Whadda ya think?
:-)

Should work, provided:

1) the amps are ground-referenced on the low side not bridged.
2) you're aware of the potentially higher current flow in the common wire.

This would surely only give half of the biwiring advantage, which is
questionable to start with...

Yes, but think how entertaining a thread about it would be :-)