The purpose of my post was to offer a helpful suggestion, not to spawn the
inevitable argument. It occurred to me that there are additional
considerations that should be aired.

1. 220V versus 120V. In a 120V country, like the U.S., one of the leads is
hot, the neutral lead is actually attached to ground at the fuse box, and,
in recent years, outlets incorporate a 3rd ground pin. This means that every
120V appliance, whether it has three wires or two, actually has one ground
attachment as is. But this is not a safety ground, because if the hot lead
in a metal box appliance somehow breaks loose, or shunts through a defective
component to ground, it can elevate the chassis to "hot", or 120V, unless
there is a safety ground, which is the purpose of the "ground" conductor.

However, this is extremely unlikely to happen in an appliance. Let's
consider plug-in lights, ie., table lamps, and floor lamps. In the U.S.,
these are all two wire devices, typically with exposed metal work. If the
zipcord in these lights somehow becomes frayed, and the hot conductor
touches the metalwork of the lamp, the lamp will become hot. If someone
touches the lamp, and a good ground, he could be electrocuted. But, the NEC,
obviously based upon a very careful risk assessment, does not require the
metalwork of the lamp to be grounded by a safety ground. The NEC authors do
not think it represents a significant shock hazard in the enviroment in
which the lamps are typically used. Note, however, that in kitchens, and
bathrooms, where water and plumbing are at close hand, the NEC has more
stringent requirements.

For many years, audio equipment was manufactured with two wire plugs as
well, up to the early 90's, in some cases. The manner of construction of
most of this equipment is identical to equipment specified for three wire
safety ground operation. Internally, there is no difference at all in the
safety considerations of the transformers for these devices. Since the early
90's, all this two-wire equipment has had polarized plugs. There is a reason
for this. One is that it is desirable that the on-off switch must break the
hot side of the circuit. The other is to take advantage of the fact that one
of the two prongs on the power cord is actually at ground potential. When a
transformer is wound, one terminus of the winding is at the iron core. The
other is on the outside. When the inner winding termination is connected to
neutral, this provides protection against a transformer short. Even if the
inside of winding shorts to the frame, which is extremely unlikely, it will
not elevate the potential of the amplifier chassis above neutral, which is
actually at ground potential.

The only other way a 2 wire amplifier, hooked to a 120V circuit, could
present a hazard is if the hot side of the line cord actually breaks away
and contacts the chassis. But there is no more risk of that than with a plug
in lamp, for which the NEC approves 2 wire operation. So, if the polarized
plug is plugged into a properly polarized circuit, a two wire stereo, OR a
three wire stereo with the ground lifted by a cheater plug, is no more
dangerous than a residential plug in light.

Eventually, the NEC moved to a higher standard, "double insulated." Modern
two wire equipment requires two separately identifiable insulating layers.
However, if the line cord breaks off internally, a chassis short could
occur. In a 120V environment, there is not much difference between so-called
double-insulated and single-insulated equipment.

This is not true in a 220 volt country. In this case, neither lead is at
ground potential. A transformer short in a two wire device will result in
elevation of the chassis above ground. The "double insulated standard" is
meaningful for two wire devices. Combined with the higher voltage, one
should take a little more care.

It is a sad fact that the balanced interconnects are not standard for home
use. A simple rule of physics says, that with the use of unbalanced
interconnects, you may have exactly ONE ground point in the entire system.
This does not make the system inherently unsafe, because the interconnects
carry enough current to at least trip a GFCI the moment a fault occurs. If
you don't have a GFCI, and a ground fault occurs, something is going to pop
or sound bad, and you will know this, which is a good thing.

If you have a very simple system, such as a preamplifier and amplifier
adjacent to each other, connected with unbalanced interconnects, you may be
able to get away with three-wire operation. But if you have a hum problem,
you will have to lift the ground on one of the components in order to break
the loop.

If you have components with balanced interconnects, you should not have to
use a cheater plug. Well, maybe, on rare occasions. But this brings up a
final point. In professional applications, the standard of safety is
different. It cannot be assumed that maintenance personnel will maintain all
levels of protection. Performers, who hold microphones in their hands, are
especially vulnerable to lapses in safety standards. In these cases, all
practices intended to preserve the safety must be rigorously observed.

Years ago most all military equipment had AC plugs that had a ground
prong that flipped over so you could use it as a two prong plug or a
three prong one. These were briefly sold at a jacked up price through
audiophile channels, and not since.

The lowest noise connection is ALWAYS when there is ONE, and only one,
connection to a good low impedance ground in the system.
Neutral-"earthy"-AND safety ground schemes are de facto ground loops in
and of themselves.

I have seen systems where the owner removed the neutral rather than
the ground connection and relied on the ground for return, or provided
his own via plumbing and/or a driven stake. It's illegal and when done
by the inept could burn down the house, But his stereo was quiet.
Oldtimers did these kind of things all the time and as long as no one
else fooled with things they usually got away with it. Needless to say
there were no guffers on those lines.

The safe, sensible solution? Two hots for POWER and a good ground. All
houses built since WWII have balanced 220 power. Properly using that is
the quietest power you are going to get and with no tweako crap
involved-which is why the high end ignores it.

"Bret Ludwig" wrote in message
ups.com...
Years ago most all military equipment had AC plugs that had a ground
prong that flipped over so you could use it as a two prong plug or a
three prong one. These were briefly sold at a jacked up price through
audiophile channels, and not since.

The lowest noise connection is ALWAYS when there is ONE, and only one,
connection to a good low impedance ground in the system.
Neutral-"earthy"-AND safety ground schemes are de facto ground loops in
and of themselves.

I have seen systems where the owner removed the neutral rather than
the ground connection and relied on the ground for return, or provided
his own via plumbing and/or a driven stake. It's illegal and when done
by the inept could burn down the house, But his stereo was quiet.
Oldtimers did these kind of things all the time and as long as no one
else fooled with things they usually got away with it. Needless to say
there were no guffers on those lines.

The safe, sensible solution? Two hots for POWER and a good ground. All
houses built since WWII have balanced 220 power. Properly using that is
the quietest power you are going to get and with no tweako crap
involved-which is why the high end ignores it.

IOW, "balanced power".
I'm not sure if this is a complete panacea for systems which have unbalanced
interconnects. Please take a look at the following gedanken experiment, and
see if you can poke a hole in it:

1. Consider two components, say, an amp, and a preamp, with unbalanced
interconnects, that have their 3rd wire safety pins connected to each other,
BUT, for the sake of this gedanken experiment, the 3rd wire safeties are not
actually attached to an external ground.

2. There is a closed loop path for electrons. An electron can start at the
preamp output, pass through the interconnect to the amplifier, out the 3rd
wire of the amp, back in the 3rd wire of the preamp, and through the
interconnect again. Thus, there is a classical closed loop.

3. From Maxwell's equations, Int{E dot dl} around the loop = d/dt { Phi } =
d/dt { Int B*dA } where A is the area of the loop.

Thus, the electromotive potential induced in the closed loop is caused by
the time rate of change of the total flux in the loop, which, assuming that
the hifi is awash in the omnipresent 60 Hz field, is roughly proportional to
the size of the loop. From the above, it can be seen that the "hum loop" is
not an effect which is caused inherently by attachment to an external
ground, but by the creation of a current loop completed by the 3rd wire
safety grounds.

Now, there are all kinds of modes, capacitive and inductive couplings, that
can produce additional hum, so the above reasoning does not say that
balanced power will not be beneficial. But the above phenomena, the
classical "ground loop" is operative even if the system is connected to a
perfectly balanced source of power. It therefore seems to me that balanced
power is probably most useful for systems that are already quite close to
optimal, such those using well balanced differential inputs/balanced
interconnects, so that the residual hum is caused by other modes.

"Bret Ludwig" wrote in message
ups.com

Balanced single phase power is not a miracle panacea but
does ensure two of the three are the same simplifying
leveling no end. This is an imperfect analogy but is
close.

Actually, balanced power ensures that no two of the three are the same.

Strictly speaking that's correct, but the two hot lines are equally
distant from the ground line at all times, except at zero crossing when
they are all the same and zero with reference to earth. When the
positive one is at positive peak the negative one is at negative peak.

In article . com, "Bret Ludwig" wrote:

Robert Morein wrote:

snip
IOW, "balanced power".
I'm not sure if this is a complete panacea for systems which have unbalanced
interconnects. Please take a look at the following gedanken experiment, and
see if you can poke a hole in it:

1. Consider two components, say, an amp, and a preamp, with unbalanced
interconnects, that have their 3rd wire safety pins connected to each other,
BUT, for the sake of this gedanken experiment, the 3rd wire safeties are not
actually attached to an external ground.

2. There is a closed loop path for electrons. An electron can start at the
preamp output, pass through the interconnect to the amplifier, out the 3rd
wire of the amp, back in the 3rd wire of the preamp, and through the
interconnect again. Thus, there is a classical closed loop.

3. From Maxwell's equations, Int{E dot dl} around the loop = d/dt { Phi } =
d/dt { Int B*dA } where A is the area of the loop.

Thus, the electromotive potential induced in the closed loop is caused by
the time rate of change of the total flux in the loop, which, assuming that
the hifi is awash in the omnipresent 60 Hz field, is roughly proportional to
the size of the loop. From the above, it can be seen that the "hum loop" is
not an effect which is caused inherently by attachment to an external
ground, but by the creation of a current loop completed by the 3rd wire
safety grounds.

You are getting way too complicated dragging Maxwell into this. Not
that that is wrong but is way too much analysis here. You need two
conductors for any single phase AC voltage. A third just screws
everything up. The earthy neutral, the hot, and the safety ground are
like a three legged stool where no two legs are the same length.

Balanced single phase power is not a miracle panacea but does ensure
two of the three are the same simplifying leveling no end. This is an
imperfect analogy but is close.

Using a two conductor cord and a big ground lug with the two conductor
cord switched to the transformer primary with a double pole switch or
linked circuit breaker, carefully shielded all the way through, and all
boxes bonded with one ground strap and it in turn hooked to earth
ground, is the ideal way to go. The UL and various international safety
agencies will not permit this, as far as I know, at least in consumer
equipment. I don't think they even permit it in commercial sound
equipment.

In such an environment balanced power would matter less. There might
still be an advantage because the fields in a balanced twisted pair
tend to cancel out relative to ground. If one side is "earthy" they do
not. Not relative to ground! That's why one side of the telephone pair
is not tied to ground. When one side of a telephone pair is "earthier"
you have what is called "AC line imbalance". Mike Sandman has a good
piece on this from a phone perspective. As we know antennas have
reciprocal patterns for transmitting and receiving, what picks up noise
well radiates noise well too.

In my homemade gaer I use two pole appliance connectors as used for
decades and an external ground lug. But if you are going to sell your
product only IEC connectors apparently are legal at least in most of
the ROW today. Elsewise they would go over to something else, because
the IEC connector really is not too good. Even the Bulgin plugs are
debatably better. Large pin plugs on older office equipment like Friden
and Monroe calculators, pre Selectric typewriters, etc. are way better
as are heating appliance plugs. Higher power portable electronics used
NEMA twistlocks, and my guess is they are still lawful in the US at
least.

The only things I have seen with a ground are commercial power amplifiers.
Most homemade stuff I have built use 2 wire cords, except for power amplifiers.
It can be a chore to start reversing 2 wire cords checking for minimum hum and noise,
when the 2 wire plugs now use polarizers.

greg

"Bret Ludwig" wrote in message
oups.com
Strictly speaking that's correct, but the two hot lines
are equally distant from the ground line at all times,
except at zero crossing when they are all the same and
zero with reference to earth. When the positive one is at
positive peak the negative one is at negative peak.

Yup, which means that none of the three voltages is the same, even though
two have the same magnitude.

"Bret Ludwig" wrote in message
ups.com...

Robert Morein wrote:

snip
IOW, "balanced power".
I'm not sure if this is a complete panacea for systems which have
unbalanced
interconnects. Please take a look at the following gedanken experiment,
and
see if you can poke a hole in it:

1. Consider two components, say, an amp, and a preamp, with unbalanced
interconnects, that have their 3rd wire safety pins connected to each
other,
BUT, for the sake of this gedanken experiment, the 3rd wire safeties are
not
actually attached to an external ground.

2. There is a closed loop path for electrons. An electron can start at
the
preamp output, pass through the interconnect to the amplifier, out the
3rd
wire of the amp, back in the 3rd wire of the preamp, and through the
interconnect again. Thus, there is a classical closed loop.

3. From Maxwell's equations, Int{E dot dl} around the loop = d/dt { Phi }
=
d/dt { Int B*dA } where A is the area of the loop.

Thus, the electromotive potential induced in the closed loop is caused by
the time rate of change of the total flux in the loop, which, assuming
that
the hifi is awash in the omnipresent 60 Hz field, is roughly proportional
to
the size of the loop. From the above, it can be seen that the "hum loop"
is
not an effect which is caused inherently by attachment to an external
ground, but by the creation of a current loop completed by the 3rd wire
safety grounds.

You are getting way too complicated dragging Maxwell into this. Not
that that is wrong but is way too much analysis here. You need two
conductors for any single phase AC voltage. A third just screws
everything up.

Bret, the above is the explanation for the definition and cause of hum
loops. It's not "too complicated"; it is simply the essence of the problem.
I'm not against your advocacy of balanced power, but an intelligent
discussion requires a real understanding of ALL the causes of spurious
currents in interconnects. The explanation I gave is subject to challenge,
but please do not dismiss it with hand waving.

Robert Morein wrote:
snip

Bret, the above is the explanation for the definition and cause of hum
loops. It's not "too complicated"; it is simply the essence of the problem.
I'm not against your advocacy of balanced power, but an intelligent
discussion requires a real understanding of ALL the causes of spurious
currents in interconnects. The explanation I gave is subject to challenge,
but please do not dismiss it with hand waving.

It's certainly not incorrect and I am not attacking it. But any time
you can avoid algebra it's a good idea to do so unless you are actually
trying to achieve a mathematical result. Usually, it's better to
communicate a process intuitively first and then give the math.
Especially to a non technical audience, of which this is certainly one.


Good grounding is senior to the issue of balanced or unbalanced power,
and good grounding is certainly possible under the current NEC.

"Bret Ludwig" wrote in message
ps.com...

Robert Morein wrote:
snip

Bret, the above is the explanation for the definition and cause of hum
loops. It's not "too complicated"; it is simply the essence of the
problem.
I'm not against your advocacy of balanced power, but an intelligent
discussion requires a real understanding of ALL the causes of spurious
currents in interconnects. The explanation I gave is subject to
challenge,
but please do not dismiss it with hand waving.

It's certainly not incorrect and I am not attacking it. But any time
you can avoid algebra it's a good idea to do so unless you are actually
trying to achieve a mathematical result. Usually, it's better to
communicate a process intuitively first and then give the math.
Especially to a non technical audience, of which this is certainly one.


Good grounding is senior to the issue of balanced or unbalanced power,
and good grounding is certainly possible under the current NEC.

Thank you. But the purpose of the math was to show that if you have a system
composed of:
1. unbalanced interconnects
2. multiple components that have three wire cords

then balanced power will not eliminate the portion of the hum which is
actually due to the "hum loop(s)".
It can eliminate or reduce whatever other hum is contributed by other means,
for example, capacitive coupling, because the two hot leads exert opposite
capacitive effects.

"GregS" wrote in message
...
In article . com, "Bret
Ludwig" wrote:

Robert Morein wrote:

snip
IOW, "balanced power".
I'm not sure if this is a complete panacea for systems which have
unbalanced
interconnects. Please take a look at the following gedanken experiment,
and
see if you can poke a hole in it:

1. Consider two components, say, an amp, and a preamp, with unbalanced
interconnects, that have their 3rd wire safety pins connected to each
other,
BUT, for the sake of this gedanken experiment, the 3rd wire safeties are
not
actually attached to an external ground.

2. There is a closed loop path for electrons. An electron can start at
the
preamp output, pass through the interconnect to the amplifier, out the
3rd
wire of the amp, back in the 3rd wire of the preamp, and through the
interconnect again. Thus, there is a classical closed loop.

3. From Maxwell's equations, Int{E dot dl} around the loop = d/dt {
Phi } =
d/dt { Int B*dA } where A is the area of the loop.

Thus, the electromotive potential induced in the closed loop is caused
by
the time rate of change of the total flux in the loop, which, assuming
that
the hifi is awash in the omnipresent 60 Hz field, is roughly
proportional to
the size of the loop. From the above, it can be seen that the "hum loop"
is
not an effect which is caused inherently by attachment to an external
ground, but by the creation of a current loop completed by the 3rd wire
safety grounds.

You are getting way too complicated dragging Maxwell into this. Not
that that is wrong but is way too much analysis here. You need two
conductors for any single phase AC voltage. A third just screws
everything up. The earthy neutral, the hot, and the safety ground are
like a three legged stool where no two legs are the same length.

Balanced single phase power is not a miracle panacea but does ensure
two of the three are the same simplifying leveling no end. This is an
imperfect analogy but is close.

Using a two conductor cord and a big ground lug with the two conductor
cord switched to the transformer primary with a double pole switch or
linked circuit breaker, carefully shielded all the way through, and all
boxes bonded with one ground strap and it in turn hooked to earth
ground, is the ideal way to go. The UL and various international safety
agencies will not permit this, as far as I know, at least in consumer
equipment. I don't think they even permit it in commercial sound
equipment.

In such an environment balanced power would matter less. There might
still be an advantage because the fields in a balanced twisted pair
tend to cancel out relative to ground. If one side is "earthy" they do
not. Not relative to ground! That's why one side of the telephone pair
is not tied to ground. When one side of a telephone pair is "earthier"
you have what is called "AC line imbalance". Mike Sandman has a good
piece on this from a phone perspective. As we know antennas have
reciprocal patterns for transmitting and receiving, what picks up noise
well radiates noise well too.

In my homemade gaer I use two pole appliance connectors as used for
decades and an external ground lug. But if you are going to sell your
product only IEC connectors apparently are legal at least in most of
the ROW today. Elsewise they would go over to something else, because
the IEC connector really is not too good. Even the Bulgin plugs are
debatably better. Large pin plugs on older office equipment like Friden
and Monroe calculators, pre Selectric typewriters, etc. are way better
as are heating appliance plugs. Higher power portable electronics used
NEMA twistlocks, and my guess is they are still lawful in the US at
least.

The only things I have seen with a ground are commercial power amplifiers.
Most homemade stuff I have built use 2 wire cords, except for power
amplifiers.
It can be a chore to start reversing 2 wire cords checking for minimum hum
and noise,
when the 2 wire plugs now use polarizers.

greg

That's what is so stupid about the "no cheater people." Most consumer
equipment doesn't provide a safety ground anyway!
BTW, you can/should run a ground from a SINGLE point on your two wire
system, to the screw on a wall plate. This will protectively ground the
entire system.

"Robert Morein" wrote in message

"GregS" wrote in message
...
In article
. com,
"Bret Ludwig" wrote:

Robert Morein wrote:

snip
IOW, "balanced power".
I'm not sure if this is a complete panacea for systems
which have unbalanced
interconnects. Please take a look at the following
gedanken experiment, and
see if you can poke a hole in it:

1. Consider two components, say, an amp, and a preamp,
with unbalanced interconnects, that have their 3rd
wire safety pins connected to each other,
BUT, for the sake of this gedanken experiment, the 3rd
wire safeties are not
actually attached to an external ground.

2. There is a closed loop path for electrons. An
electron can start at the
preamp output, pass through the interconnect to the
amplifier, out the 3rd
wire of the amp, back in the 3rd wire of the preamp,
and through the interconnect again. Thus, there is a
classical closed loop. 3. From Maxwell's equations, Int{E dot dl}
around the
loop = d/dt { Phi } =
d/dt { Int B*dA } where A is the area of the loop.

Thus, the electromotive potential induced in the
closed loop is caused by
the time rate of change of the total flux in the loop,
which, assuming that
the hifi is awash in the omnipresent 60 Hz field, is
roughly proportional to
the size of the loop. From the above, it can be seen
that the "hum loop" is
not an effect which is caused inherently by attachment
to an external ground, but by the creation of a
current loop completed by the 3rd wire safety grounds.

You are getting way too complicated dragging Maxwell
into this. Not that that is wrong but is way too much
analysis here. You need two conductors for any single
phase AC voltage. A third just screws everything up.
The earthy neutral, the hot, and the safety ground are
like a three legged stool where no two legs are the
same length. Balanced single phase power is not a miracle panacea
but does ensure two of the three are the same
simplifying leveling no end. This is an imperfect
analogy but is close. Using a two conductor cord and a big ground lug
with
the two conductor cord switched to the transformer
primary with a double pole switch or linked circuit
breaker, carefully shielded all the way through, and
all boxes bonded with one ground strap and it in turn
hooked to earth ground, is the ideal way to go. The UL
and various international safety agencies will not
permit this, as far as I know, at least in consumer
equipment. I don't think they even permit it in
commercial sound equipment. In such an environment balanced power would
matter
less. There might still be an advantage because the
fields in a balanced twisted pair tend to cancel out
relative to ground. If one side is "earthy" they do
not. Not relative to ground! That's why one side of the
telephone pair is not tied to ground. When one side of
a telephone pair is "earthier" you have what is called
"AC line imbalance". Mike Sandman has a good piece on
this from a phone perspective. As we know antennas have
reciprocal patterns for transmitting and receiving,
what picks up noise well radiates noise well too. In my homemade gaer I
use two pole appliance connectors
as used for decades and an external ground lug. But if
you are going to sell your product only IEC connectors
apparently are legal at least in most of the ROW today.
Elsewise they would go over to something else, because
the IEC connector really is not too good. Even the
Bulgin plugs are debatably better. Large pin plugs on
older office equipment like Friden and Monroe
calculators, pre Selectric typewriters, etc. are way
better as are heating appliance plugs. Higher power
portable electronics used NEMA twistlocks, and my guess
is they are still lawful in the US at least.

The only things I have seen with a ground are commercial
power amplifiers. Most homemade stuff I have built use 2
wire cords, except for power amplifiers.
It can be a chore to start reversing 2 wire cords
checking for minimum hum and noise,
when the 2 wire plugs now use polarizers.

greg

That's what is so stupid about the "no cheater people."
Most consumer equipment doesn't provide a safety ground
anyway!

Well dooh! Its not like we had problems with the suggestions that
no-polarized plugs be reversed.

"Robert Morein" wrote

You are getting way too complicated dragging Maxwell into this. Not that
that is wrong but is way too much analysis here.
You need two conductors for any single phase AC voltage. A third just
screws
everything up.

Bret, the above is the explanation for the definition and cause of hum
loops. It's not "too complicated"; it is simply the essence of the
problem.
The easy solution, most of the time, is to
use a power line conditioner with isolated
transformers. Over the years I've found
many electrical outlets which are improperly
wired. Having open hot, hot/grd or hot/neu
reversed. You assume the risk to your
equipment when you use a cheater plug
under those conditions.

And finally, there is no easily available
method to determine the quality of the
ground wire at the outlet. Maybe you
should use that huge intellect of yours
and invent one.

"Arny Krueger" wrote in message
. ..
"Robert Morein" wrote in message

"GregS" wrote in message
...
In article
. com,
"Bret Ludwig" wrote:

Robert Morein wrote:

snip
IOW, "balanced power".
I'm not sure if this is a complete panacea for systems
which have unbalanced
interconnects. Please take a look at the following
gedanken experiment, and
see if you can poke a hole in it:

1. Consider two components, say, an amp, and a preamp,
with unbalanced interconnects, that have their 3rd
wire safety pins connected to each other,
BUT, for the sake of this gedanken experiment, the 3rd
wire safeties are not
actually attached to an external ground.

2. There is a closed loop path for electrons. An
electron can start at the
preamp output, pass through the interconnect to the
amplifier, out the 3rd
wire of the amp, back in the 3rd wire of the preamp,
and through the interconnect again. Thus, there is a
classical closed loop. 3. From Maxwell's equations, Int{E dot dl}
around the
loop = d/dt { Phi } =
d/dt { Int B*dA } where A is the area of the loop.

Thus, the electromotive potential induced in the
closed loop is caused by
the time rate of change of the total flux in the loop,
which, assuming that
the hifi is awash in the omnipresent 60 Hz field, is
roughly proportional to
the size of the loop. From the above, it can be seen
that the "hum loop" is
not an effect which is caused inherently by attachment
to an external ground, but by the creation of a
current loop completed by the 3rd wire safety grounds.

You are getting way too complicated dragging Maxwell
into this. Not that that is wrong but is way too much
analysis here. You need two conductors for any single
phase AC voltage. A third just screws everything up.
The earthy neutral, the hot, and the safety ground are
like a three legged stool where no two legs are the
same length. Balanced single phase power is not a miracle panacea
but does ensure two of the three are the same
simplifying leveling no end. This is an imperfect
analogy but is close. Using a two conductor cord and a big ground lug
with
the two conductor cord switched to the transformer
primary with a double pole switch or linked circuit
breaker, carefully shielded all the way through, and
all boxes bonded with one ground strap and it in turn
hooked to earth ground, is the ideal way to go. The UL
and various international safety agencies will not
permit this, as far as I know, at least in consumer
equipment. I don't think they even permit it in
commercial sound equipment. In such an environment balanced power
would matter
less. There might still be an advantage because the
fields in a balanced twisted pair tend to cancel out
relative to ground. If one side is "earthy" they do
not. Not relative to ground! That's why one side of the
telephone pair is not tied to ground. When one side of
a telephone pair is "earthier" you have what is called
"AC line imbalance". Mike Sandman has a good piece on
this from a phone perspective. As we know antennas have
reciprocal patterns for transmitting and receiving,
what picks up noise well radiates noise well too. In my homemade gaer
I use two pole appliance connectors
as used for decades and an external ground lug. But if
you are going to sell your product only IEC connectors
apparently are legal at least in most of the ROW today.
Elsewise they would go over to something else, because
the IEC connector really is not too good. Even the
Bulgin plugs are debatably better. Large pin plugs on
older office equipment like Friden and Monroe
calculators, pre Selectric typewriters, etc. are way
better as are heating appliance plugs. Higher power
portable electronics used NEMA twistlocks, and my guess
is they are still lawful in the US at least.

The only things I have seen with a ground are commercial
power amplifiers. Most homemade stuff I have built use 2
wire cords, except for power amplifiers.
It can be a chore to start reversing 2 wire cords
checking for minimum hum and noise,
when the 2 wire plugs now use polarizers.

greg

That's what is so stupid about the "no cheater people."
Most consumer equipment doesn't provide a safety ground
anyway!

Well dooh! Its not like we had problems with the suggestions that
no-polarized plugs be reversed.

The problem that you have, is that you insist that people discard their
perfectly good equipment that happens to have a 3 wire cord, and unbalanced
interconnects.
This is, for many people, an economic hardship. It is for this reason that
I have explained how one can use cheater plugs, combined with a GFCI, the
interconnect grounds themselves, and a bit of awareness, with a residual
level of risk that has not produced any victims in a planet of 6 billion
people.
BTW, I prefer your solution. It just isn't workable for most of us.

"Powell" wrote in message
...

"Robert Morein" wrote

You are getting way too complicated dragging Maxwell into this. Not that
that is wrong but is way too much analysis here.
You need two conductors for any single phase AC voltage. A third just
screws
everything up.

Bret, the above is the explanation for the definition and cause of hum
loops. It's not "too complicated"; it is simply the essence of the
problem.
The easy solution, most of the time, is to
use a power line conditioner with isolated
transformers.

I have shown with Maxwell's equations that, with systems that have
unbalanced interconnects, the solution you propose above is insufficient.

It will solve a problem if the particular hum loop is caused by an external
connection to ground at more than one point. However, due to the fundamental
induction law derived from Maxwell's equations, it is sufficient to have hum
merely to have two three wire cords where the 3rd prongs are connected to
each other, even if the connection point is not connected to an external
ground.