Well, it is hard to say. I remember once that a coil of speaker wire was laying across a poor quality power bar and it was causing an inductive hum. My background in electronic/electrical engineering tells me theoretcially that this is going to happen, but it does not always happen. Is the are clear of any other intereference sources? Is the electrical circuit stable and properly grounded? I don't believe this is an issue, because it would/could cause greater noise across the board.
Do you get this in any source when played? You can try isolating the amp and speakers from the source by unplugging the input side of the source connectors into the amp, and checking the noise.
Can you swap out the amp for another? It is not inconceivable that you have a channel problem. But that is a major statement. How old is the piece? What is the piece?
I think you need to isolate the probable sources of the problem. Try the speaker first. If the replacement also exhibits the noise, I would suggest moving towards isolating the amp.
Regards,
BBIBH
