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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
curiousjim's avatar
curiousjim
4,860 posts
 

There’s something going on if it’s happening to both of your amps.

A few weeks ago, my wife was in the basement and turned on a space heater. A while later, I turned on my integrated upstairs and it started to hum. It had never done it before and I had no idea she turned on the heater. It took me days before I figured out what had happened. I had to call the manufacturer.

They called it DC Coupling.

Do you have led lights?  Even Xmas lights can cause a hum.

 

lowrider57's avatar
lowrider57
5,417 posts
 

HumX doesn't always work, cheater does.

designsfx
795 posts
 

@ervikingo 

Have a look through this document- maybe something helpful.

AES

holmz's avatar
holmz
2,328 posts
 

If nothing is plugged in (ICs) then it would be difficult to get a loop, so difficult to get a ground loop.

A DC bias on the AC line, usually comes across as transformer hum.
I ‘m not sure how it would come out of the speakers though.

ervikingo OP
166 posts
 

Only thing I cannot disconnect is the power meter and a whole house surge suppressor that is right after the power meter. I have a standby generator but it’s isolated when there is power by an automatic transfer switch. 
 

all lighting are LED but the noise is present with all circuit breakers (but the amps) tripped. 
 

I have no hum on my solid state monoblocks which share power outlets (for testing they are disconnected) and are located near by. 
 

Odd that it takes a bit to start. You see the glow of the tubes change. 
 

would speaker feedback do that? IRS Beta 

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