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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
ervikingo OP
164 posts
 

Monday morning update.  I couldn't wait for the "good tubes" to come for testing.  I ordered one from Amazon (overnight delivery!) and the noise is completely gone.  Its scary quiet!

I ordered new 7044 as one of them is not up to par (still some noise).  I moved the 12 AT7 from one amp to the other and there was noise on the other amp; moved the 7044 from the quiet amp to the other and the noise is gone.

Huge lessons learned:

- there are a lot of enthusiasts out here who are willing to help

- @atmasphere is an awesome resource 

- start with the basics; I have spent weeks and $$$ chasing after the noise and never thought to check if the prior owner had used the proper tubes

I'll post again once both 7044 and 12AX7 have been replaced with the 12AT7.

Please accept my most sincere thanks for your help (and for the humor...  trolling with the motorboating sound...!)

dweller's avatar
dweller
3,793 posts
 

"I have replaced the tubes and both amps were just tested at the factory."

You're telling us the factory didn't notice you were using the wrong tubes?

Sheesh.

jea48
4,486 posts
 

@ervikingo

The 7044 tube is the Driver tube...

I would strongly suggest you tell the vendor you buy them from you need each section of the Triode tightly, closely, matched. Pay extra for each tube if you have to.

I doubt you will get that from Amazon.

.

ervikingo OP
164 posts
 

@jea48 UHUM.  I didn't order the 7044 from Amazon.  Only a 12AT7 as a tester (TungSol) while the good ones arrive from Manley (7044 and 12AT7).

@dweller regretfully they did not.  The spec'd tubes for the Snapper changed and they now use the 12AX7, my vintage didn't.  Occam's Razor

ervikingo OP
164 posts
 

@jea48 since we are on this, any recommendations on tubes or suppliers?

12AT7, 7044, EL-34, KT77?

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