Thorman may have your answer.
If you have cable tv, try to take the cable wire out of the first point of entry into the system, which is probably a cable box. But remember, disconecting the cable box would not show anything. Only taking that cable wire out will tell you if it's the problem. If your amp hums after that, it's something else. But if it's the cable tv, musicdirect.com sells this little thing called Mondial Magic Box
http://www.amusicdirect.com/products/detail.asp?sku=AMONDBOX
My amplifier was humming and it was the cable tv, so I bought it at music direct. Problem solved....Good luck.
If you have cable tv, try to take the cable wire out of the first point of entry into the system, which is probably a cable box. But remember, disconecting the cable box would not show anything. Only taking that cable wire out will tell you if it's the problem. If your amp hums after that, it's something else. But if it's the cable tv, musicdirect.com sells this little thing called Mondial Magic Box
http://www.amusicdirect.com/products/detail.asp?sku=AMONDBOX
My amplifier was humming and it was the cable tv, so I bought it at music direct. Problem solved....Good luck.