Re: Preamp causes hum even when off

tomg@xxxxxxxxxxx wrote:
Can anyone shed some light on possible reasons that a tube-based
preamp could cause the main power amplifier to produce hum, even when
the preamp is not powered? It also causes the hum when unplugged, as
well as when powered and in use. Other signal sources do not cause
the main amplifier to hum. Other than causing the hum, the preamp
sounds good.

Possibly a ground loop..
Does it hum with all of the sources connected to the preamp?
Does it go away if you disconnect the sources one by one? Perhaps it only does it when,(say)the CD player or TV/DVD is connected.

Is the internal wiring in the preamp in good shape?
The signal carrying wires are all shielded,etc.?
Might be poor shielding,but probably not likely.

A couple cents. :-)
.

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