Hum is almost always ground related. There can be instances where ac or dc is affecting the sound, and I would suggest looking at the electrical outlets you have these plugged into as well. Are the polarities of the plug(s) correct? Are they on the same circuit breaker? If so, are they properly grounded electricaly? If not, are they proper connected at the electrical panel? It is not a mandate that each piece (cd, receiver, etc) have 3 prongs on the cord. It is required that the polarities be correct for the electrical outlet, especially if there are 2 prongs on a polarized plug.
Also, I would suggest anyone who is considering a serious system, HT or music to make sure the electrical cirsuits are properly installed. If you can have them installed, isolated circuits are definitely the way to go. Power bars and the like are really stop gap measures.
Regards,
BBIBH
