Good point Michael. I took your suggestion.
I turned off all of the breakers except the one controlling the outkets in my HT. Then, I unplugged every device plugged into that circuit, except for the receiver. The receiver has nothing plugged into it except for 4 speakers.
There was still a hum!
BTW, I tried a cheater plug with no luck. I did not reverse the polarity by filing down the plug and inserting backwards, though.
Again, the hum is audible from a few feet away with the volume all the way down and then with increased volume, a hum gets louder. It actually sounds like a different hum gets louder, if that makes sense.
Here are my current theories:
1. I have unrealistic expectations of how quiet a recevier should be.
2. My old Sony receiver (and another old Sony receiver I have) have poor quality amps that produce noise.
3. I have noise in my power that is carrying though to my speakers. I previously did not believe this was possible, but I am not sure anymore.
Maybe I need an AC isolation transformer??
Help!
