Great suggestion, Neon. Those dimmers radiate all kinds of garbage because many are unshielded. I had a friend in Toronto who was devoted to a CBC radio station on the AM band and he complained to me about a terrible buzzing he was getting, making the station unlistenable. He'd just had his place renovated with all kinds of dimmers, so I used a portable radio as a kind of signal tracer and as you got closer to the dimmer switch the buzz increased. Once the dimmers were gone, AM reception was clear.
Argon should also unplug the cable-TV feed (or satellite feed) where it enters the cable box or satellite receiver and see if the hum goes away. Those are most often the source of ground voltage differences causing ground loop hum.
Alan
