Hum on Tube Amp - Can't find source


I have a hum (60hz) I can hear on my speakers and it happens with my tube monoblocks (either of them).  With or without interconnects, it even happens on either amp (have tried one at a time) with every circuit on the house tripped/disconnected, every other component disconnected from the wall (including the Internet/CaTV line) and no interconnects.  

One amp has it as soon as it warms up whereas the other one is intermittent.

Hum X doesn't solve it, iFi Ground defender either, AVA HumDinger on powerline  doesn't solve it either.

I have replaced the tubes and both amps were just tested at the factory.  Replaced the circuit breaker, tightened every wire on the breaker box, checked and cleaned all connections to ground rod.  Added a hum eliminator to the internet line.

Hum cycles a bit with the tube glow matching the cycles.

I'm waiting on the power company to come check the power coming to the house.

Thoughts?

ervikingo

Showing 2 responses by cleeds

You might want to try these amps in a different location to see if you get a different result, but I doubt you will. Even though the amps have been recently checked, they sound suspect to me. Many an amplifier or vacuum tube set have passed a bench check only to suffer some shipping damage on the way back to the customer.

What kind of amplifiers are they?

... Next is taking amps to test at my office. 

I think that will reveal the amps are the source of your problem.