Listen to Newbie, he has the right solution for you. If you have TV cable hooked up anywhere on your system, that is the first place to look.
Transformer Hum
I own a few vintage amps, two Citation 16A's, an Ampzilla, a Son of Ampzilla, and a recently aquired AEA 620. Is it normal to have transformer hum coming back through the speakers? Could I have other issues like RFI from a LCD rear projection tv or interconnects that aren't sheilded well? Or is the age of the equipment the main concern? Then there is the grounding issue. I don't know where to start. Thank you for any thoughts or advice.