Power Amp transformer hum - intermittent and increases and decreases in a few seconds

I think it's dc getting into my line too. Very frustrating. 

My problem was hum with dryer/dishwasher/blow dryer/fluorescent lights/dimmer switches being used, and that's with a dedicated line to the listening room. The above posters have already given you all the information you need. Hope you get it resolved soon.

Tom

Thx Tom!

You are very welcome! That's what this site is for. Lot's of great people on here! I've been helped many times in the past and am grateful for that and for the chance to help others if I can. 

Tom

FYI, One of my many power amps, a Smart Theater Systems TA 242 ( which is actually a beefed up Hafler 220 by design, and very musical ), experiences the transformer hum ( toroidal, chassis only ), when I use my OTR microwave. Have not tried a cheater plug during these times, as it is always in rotation with others. Enjoy ! MrD.