Thanks to both of you.
I will borrow a volt meter XM but could you tell me what am looking for in numbers? Sorry but I never had a use for a volt meter. My electrical circuit breaker box was rewired and updated about five years ago and since that time I did add two 20 amp circuit breakers to the HT room b/c I was thinking about a future update for my amplifier...the 7900. I never purchased the 7900. My electrician assured me that i could install the additional 20 amp breakers and more if I wanted.

The hum is constant. Low but constant. Yet, during the spring and summer non-existent.

Thanks again