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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
dweller's avatar
dweller
3,741 posts
 

Do the P.S. Audio Power Plants eliminate hum from tube amps? Know first-hand the heartbreak of Tube hum (Prima Luna Prologue Premium w/Klipsch LaScalla II).

This would be a godsend.

allears4u
129 posts
 

Put together any tube amp and the hyper efficient Klipsch Lascalas (or Klipschorn) and that efficiency will dredge the bottom of the amp's circuit mercilessly revealing the slightest hum, Paul Klipsch must not have minded this issue. (Early on he used tube amps until later Crown SS)  Admittedly, all is forgiven and forgotten once the music is playing. However, pauses or gaps in the stream of music and HELLO there's the hum again! Being OCD, i.e. today's audiophile, and introduce said hum, and no matter how minuscule it can become deafening. Like most who are in this spot we have applied every tweak possible. And we have had a measure of success. But tube amps use tubes. Tubes are a moving target  They are like candles gradually burning out. As a consequence, noise can increase here and there among the family of tubes as they interact with each other. The last couple days, after a month of nearly continuous (nearly) silent operation, no matter what I did, the hum had once again risen above my personal limit. After doing my due diligence and double checking the common culprits, I was defeated. Then on a whim I rotated the power tubes leaving the same but moving the big ones around. Hum GONE! Why is that?  

allears4u
129 posts
 

Interesting change in what little "hum" I have left after Raven upgraded the grounding loop system. I just I'm OCD about a totally black background. I rearranged my room where now I sit 3 feet further back from speakers. For some reason I'm now out of reach of a low frequency "hum" that I can reacquire audibly if I lean forward those 3 feet! In the meantime the soundstage and detail etc. are all still excellent. Weird but nicely so. My volume goes up a tad at this increased distance which also helps. (I have an off topic quick question...does anyone know the best DB's on the Lascalas where they produce their best sound? 70? 80? 90?) 

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