Balanced cables will solve the problem if its radio frequecy interference. You should disconnect your preamp and amp and then listen for hum. If its still there its probably an amp problem. You mentioned a refrigerator motor. That's easy. The motor doesn't run all the time so when the compressor is finish cooling down the frig and the motor goes off then the hum would go away. More likely its your preamp. I owned an ARC LS2B and used it in the balanced mode. It caused hum and when I connected anything associated with the TCI/AT&T TV cable system the hum got unbearable. I changed to a Sonic Frontiers LS3 and the hum went away. Are you using the three prong power plug on your ARC or did you have to use a cheater and go to just the two prong configuration? I had to do that the day I bought the ARC. This work as long as everything else behaves properly vs grounding.
Balanced lines solve hum problems?
I'm having a real tough time killing a low level hum coming out of my Martin Logan Quest speakers. The set up consists of an Oracle Delphi IV and YBA CD Integre source components, fed into a Audio Research SP9 Mk II Pre-amp. 25' single ended interconnect to a pair of bridged Classe Audio DR-8 amplifiers. From there, (8) 8' runs of speaker wire to the Quests complete the system. I've put in hospital grade plugs, and grounded the amps to a cold water pipe, a little better, but still a hum exists. One of the guys I work with feels I have a 100hz hum, likely coming from a motor (i.e. fridge). He has suggested I change from single ended to balanced lines, and the problem ought to go away. To do so, means inserting a DI box in the signal path to convert single ended to balanced signals, via an isolated transformer, I'm not in favour of this approach. Another option is to sell my Audio Research pre-amplifier I love (great phono section) and find another pre-amp with balanced outputs, more than likely a line stage pre-amp that requires a seperate phono stage. Much money and hassle, is this the only way to solve this problem? Opinions are most welcome, thanks, Jeff