Try moving to the opposite phase at the breaker box and see if that solves the problem. If your ceiling fan has a re-stat speed control, it may be the source of the hum.
Dedicated circuit picking up noise
I installed a dedicated circuit for my system, yet I'm still getting a hum through my speakers. Also, when I switch on a ceiling fan in the same room as my system, I get a loud pop. What gives? I thought a dedicated line would eliminate ground loops and isolate noise from any other circuit. Any ideas are appreciated