wrote in message
oups.com...
That was my thought too, that the injected signal from the GFCI may be
the source of the problem. But one would think that the signal would
be designed so that it would not cause problems with properly
functioning power supplies in electrical eqpt. So, it seems possible
the real problem may be with the amp.

I actually was a bit inaccurate in my original response. The signal is
typically full-wave pulses (120 hz) zero-referenced by a capacitor. It is
therefore a 120 hz ac signal with sharp points, which produce harmonics. The
higher frequencies will find their way into the amp more readily than the 60
hz power. A marginal amplifier design certainly could make the problem
worse, while a good design might be unaffected. There could also conceivably
be differences in the injected signal from one GFCI manufacturer to another.

Of course, I could be wrong, and one of the other responses could be
correct. The proof would seem to be in the fact that plugging it into
another outlet resolves the problem.

Ben Miller
--
Benjamin D. Miller, PE
B. MILLER ENGINEERING
www.bmillerengineering.com