[Don Pearce[_3_]]

On Mon, 6 May 2013 10:02:21 -0700, "Bob F"
wrote:

Don Pearce wrote:
On Mon, 6 May 2013 07:08:15 -0700, "Bob F"
wrote:

Don Pearce wrote:
On Sun, 05 May 2013 23:04:35 -0700, isw wrote:

Looks OK to me. It's configured as a series common mode stopper.
What's the problem?

Will this design eliminate ground loop problems? My concept of
baluns was that
they isolated the two ends by placing them on opposite windings
of a transformer. I am no expert, which is why I asked.


That is a different thing. You need a transformer to kill a ground
loop entirely, but yes, provided there is enough inductance in the
coils this will still make a good job of getting rid of hum from a
ground loop.

If there's enough inductance to attenuate 60 (or 50) Hz from the
power line, why won't it do the same for similar frequencies in the
desired signal?


No, because of the way the windings are arranged their inductances
cancel each other out for the audio signal, but not for the induced
hum.

The windings being on a transformer arranged so that common mode
noise cancels, and the signal doesn't?


That's it. The windings are wound in the same direction on the two
sides. That means that the forward and reverse signal currents on the
two windings are always in opposite directions magnetically. So the
signal doesn't see any net inductance.


Is this design going to avoid ground loop problems? Those signals would just be
on the one side, so would they be canceled?



The ground loop is fixed by the inductance presenting a huge series
impedance to the hum current, which only passes along the ground wire.
There is no equal return current in the signal wire to cancel the
inductance.

d