Re: More on cheater plugs


"GregS" <szekeres@xxxxxxxx> wrote in message
news:dvs8d3$r72$2@xxxxxxxxxxxxxxxxxxxxxxxxxxxx
In article <1143054619.433474.42670@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>, "Bret
Ludwig" <bretldwig@xxxxxxxxx> 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.


.

Relevant Pages

  • Re: More on cheater plugs
    ... 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 ... There is a closed loop path for electrons. ... In such an environment balanced power would matter less. ...
    (rec.audio.opinion)
  • Re: More on cheater plugs
    ... with unbalanced interconnects, that have their 3rd ... wire safety pins connected to each other, ... There is a closed loop path for electrons. ... Bulgin plugs are debatably better. ...
    (rec.audio.opinion)
  • Re: More on cheater plugs
    ... with unbalanced interconnects, that have their 3rd ... wire safety pins connected to each other, ... There is a closed loop path for electrons. ... Bulgin plugs are debatably better. ...
    (rec.audio.opinion)
  • Re: Ground Busses
    ... Someone suggested I write an article on power and grounding techniques ... be no need to worry about power and ground topologies or wire routing. ... By definition, every circuit forms ... strong field from a transformer or choke) exists in the loop, ...
    (rec.audio.tubes)
  • Re: Ground Busses
    ... Someone suggested I write an article on power and grounding techniques ... be no need to worry about power and ground topologies or wire routing. ... By definition, every circuit forms ... strong field from a transformer or choke) exists in the loop, ...
    (rec.audio.tubes)
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