Try this -- I am assuming that you have 120VAC mains -- make the following
filter --

1) from the two mains leads at the plug end, a 47nF/250 VAC capacitor
2) each mains lead connects to a 470 uH choke,
3) across the first outgoing choke leads, a 100nF, 250 VAC capacitor
4) a second choke consisting of two 2mH windings on the same core
5) a 100nF/250 VAC cap

The cores and windings have to be "beefy" enough to handle a couple amps.
You might be able to get away with using the cores from a PC power supply.

This is the transient supression circuit in one of the ARRL switching power
supply designs. It works in both directions.

wrote in message
...
I have an integrated amplifier that passes every spike and glitch on the
the mains, generated from motors and transformers turning off/on in the
house, even though I ran a dedicated feeder off the mains breaker panel
to the "audio room".
My other gear does not suffer from the sensitivity, so I am wondering
what I can add to this particular amp to make it more immune to power
line transients. Varistors or caps across the mains switch, ferrite
beads, etc? Any advice is appreciated.

Arcsound