Loud Hum

Is it dimmer hum of ground loop? Good explanation at[http://www.audioadvisor.com/store/productdetail.asp?sku=TRIBGG1&product_name=Ground%20Guard%201%20Ground%20Loop%20Eliminator] Turn off dimmed lights. Hum? Unplug cable. Hum? Ground loops (caused by the cable being grounded at a different potential from your electrical cable) can also be at your equipment. Unplug all video RCAs. If there is still hum, use 3 to 2 prong "cheater" plugs from the hardware store to remove grounds from all bu preamp. If the hum is from video you may need cheaters and cable ground isolator on video grounds.

Just a quick question about isolated circuits. If you run the ground to a point outside the AC panel, I can understand that. But, since the neutrals of the circuit have to be connected to the same common ground(neutral buss, both ground and neutral go here) buss in the panel, how are you isolating the circuit from the same noise that might ride in on the ground and keep it off the neutral?

Thank you for all your responses. I have one basic question. THe hum is there even when the lights are out. Could this be caused by the dimmer even if the lights are out? Also, when I disconnect the interconnects from the pre amp the hum is gone (mostly). Could it be the cables I am using?
The B15 actually is on a "cheater" (no ground) but it still has the "Hum". I am not sure (and honestly I doubt) that the electrician that installed the dedicated power lines for the amps also used a separate ground. I will do this if it is necessary. The worst hum is coming from the proceed running the surrounds and center (this amp is not connected to a dedicated power line).

My 7BST's have a ground loop switch on the rear panel. If your amps have this just flick the switch.

Dynasys- No, if you turn off the lights, and the hum remains, it's a ground loop problem. Good thing; you don't have to listen in the dark! You don't need a separate ground for the wiring. In my system, I had a terrible time getting rid of the hum. My Plinius pre-amp had no ground switch (internal cheater?) which helped a little. Eventually I had to put a cheater on everything but the preamp ( I plugged everything into a PSAudio plugstrip,except the power amp. I put a cheater on the plug strip. I still had the hum. I unplugged the cable. Less hum. I put a cheater on the power amp. The hum went away...) I also bought a coax ground cheater to divorce the cable from the ground (you can get the mondial magic isolator from audioadvisor.com for 100 bucks.