Matt, I experienced a similar problem when I switched from a Marantz Amp to Levinson. Speakers hummed throughtout and during quiet passages, you could hear the hum come through. Very frustrating. After much searching and lifting grounds, etc. I found the hum to come from my mains! The biggest culprit was a fridge connected to the same power phase (note not circuit). Problem was solved by:
- an engineer who moved noisy circuits to other phases (I have 3 phase power supply in my home)
- installing a high current capable passive line conditioner
- an engineer who moved noisy circuits to other phases (I have 3 phase power supply in my home)
- installing a high current capable passive line conditioner