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Diagnosing and fixing transformer hum

Moved into a house two months ago and have (finally) set up the system in the living room. (The plan is to turn the unfinished basement into a listening room.) Amplification is all tube, with a push-pull 20w 300b integrated amp. The transformers in the integrated hum loudly; there was only a very mild hum when we were in our condo, quite tolerable when sitting close to the amp.  The house was built in 1941. Even light fittings seem to hum. 
Things I have tried:
1. Different wall sockets
2. Switching off appliances 
3. Turning off all other circuits from the electrical panel except for the wall socket in question. 4. Using an Emotiva CX2 DC blockerIn all cases, no improvement. Any suggestions to diagnose, isolate, and fix?

pingvin
pingvin
tuberist
951 posts
 
Ping, I’m not sure if this is helpful but I would use a circuit tester on your home’s outlets to see if they are wired properly. I also would call an electrician to see if your service panel is setup correctly, grounded, breakers ok etc. sorry you’re having this issue. when you solve this would you let us know what you discovered and did? Finally, what did your amp mfg. have to say about your issues?

noromance's avatar
noromance
9,902 posts
 
If it's not DC offset, it may be that the transformer(s) are simply loose enough to vibrate. Have you tried loosening/tightening mountings bolts? 
three_easy_payments's avatar
three_easy_payments
2,097 posts
 
With one particular amp I owned, and after trying everything possible, the only culprit remaining was delamination "rattle" from loose windings over time. Sometimes the transformer is simply bad...and an electrician isn't going to help anything.  It's the only amp that's ever hummed in my setup at the same house - tube or SS.  
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