why is this thing humming?

I turned on a movie this morning and the hum is very apparent in the sub woofer also. Probably louder for the most part through the sub. Now im getting aggervated.ahhhh.Thats better does this change any thing? I tried changing the sub cable and it did nothing. I had a sub cable befor that waqs the cause of a hum on a previous system but this time no luck. Thanks in advance Matt

Rich thanks for the input Ill give it a shot tommorow thatll be the first thing on my to do list! Ill keep you posted.

Im sorry I may have not given enough info. The hum is coming from the speakers it isnt as apparent after the music is being played at moderate levels but I dont think the hum goes away. Matt

Yes there is a dimmer in line with this Ive got the electrician comin to run a designated outlet with 10 guage wire and its own circuit!