Hum on Tube Amp - Can't find source

The only thing I can think of, if you haven't done so already, is to disconnect the cable from your TV cable box or TV itself and also the modem to eliminate any effect it could have.

I had your situation and the hum ended up coming from my TV cable.  Attached a Jensen VRD-1FF CATV isolator and it took care of my problem.  However, I had my cable box L&R audio feeding into my tube preamp and as I remember using a cheater stopped the hum.  But worth a try.

take them to a friends house.

no input needed, just hook to speakers, plug in:

hum? it’s the amps.

if amps, analyze differences if any l/r time before hum starts? time hum changes?

no hum, it ain’t the amps.

go from there with confidence it is or is not the amps.

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btw, have you hooked them up to an easily movable small set of speakers, different 2 way crossover, any difference?

Amps are Manley Snappers

will try with my Aerial speakers and see. After that, going to call on a neighbor and bring them in

i ran a long extension cord to an outdoor outlet and problem persisted

I installed a ground trap on the internet line. Going to disconnect it outside the home to take it out of the ground circuit

is there a link to the Stereophile article about the transfer switch?

thanks to all

Had this problem with a Primaluna Prologue Premium and Klipsch LaScallas.

Sent amp to Upscale Audio (Indianapolis to L.A.) who checked out the amp and said it was working normally.

Never fixed the problem so I sold the amp.

I believe the problem is/was in my main panel but didn't want to hire an electrician.

Doesn't affect my current equipment. Good luck.