Ground Loop Issues

I know this topic has been kicked around many times on this website, but I have not found the answer I am looking for. The current setup has a pair of Bryston 7B-ST monos plugged directly into a 20 amp dedicated circuit. The rest of the system is plugged into a Chang (CLS 9600)power conditioner which plugs into a separate 20 amp dedicated circuit. The rest of the system is a Denon CD player (DCD-1650), ARC LS3 or Cary SLP88 preamp. I also have a VPI table and ARC PH3 phono stage, but they have been removed from the system while I try to figure this out. Right now the only way I can get rid of the hum and noise is to use a cheater plug on the preamp (either preamp)and flip the switches to float the ground on the Brystons. I am baffled as to why I would have to float all of the 3-prong plugs instead of either the preamp or the amps. I should also mention that this same problem exist when I put my spare Hafler amp (9505) in the system. I don't think the problem is the equipment. Any advise is appreciated. Thanks, Scott