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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
Ag insider logo xs@2x
cleeds
5,947 posts
 

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?

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lloydc's avatar
lloydc
751 posts
 

Could you take an amp to a friend’s house and insert it in their system?  That would answer whether it us the amp or something in your house’s power system.  
 

MF’s article in Stereophile about the generator he installed would lead me to suspect your “automatic transfer switch”.

fuzztone's avatar
fuzztone
5,598 posts
 

@lowrider57

Maybe for you. Maybe... Any time I’ve tried a HumX I’ve followed negative results with a physical "cheater."

NEVER different for me.

Your assertion is easily proven with making a YouTube video.

jetter
3,033 posts
 

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.

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