"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.