Need Help with Strange Buzzing

Hi. Every night at about 6:00pm my speakers start buzzing...its not usually a very low buzz, more of a midrange noise, that is especially hard on the tweeters. It only makes the noise at night so far as I can tell. Sometime during the night it stops, because it isn't there in the morning. I have been turning my system off at night since I noticed it. I think it has something to do with the apartment that I live in. It is old and the wiring may be old. My stereo only makes the noise when my amp is on (if I turn my cd player and pre amp off it still makes the noise.) I am wondering if there is some way to fix this problem (such as buying new power cords). I'd be interested in hearing if anyone else has ever had this problem.

Just in case this helps, here is my system:

Rega Planet 2000
Adcom GFP-750
Classe CA-100
Paradigm Monitor 7v.2
MIT Terminator 4 interconnects
Tara Labs Prism Bi-wire
Panamax 6 (surge protector)

Any help will be appreciated. I can really only listen to my system at night and this has really made listening unenjoyable.
It sounds like you're getting induced noise through the power line - perhaps from a flourescent light or electric motor. Your Panamax 6 doesn't seem to provide any power line noise supression. Try one and see if it helps.

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Thanks for the help. Can you recommend a reasonably priced noise suppressor? Any other suggestions?