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Steve f
Reply with quote  #1 
What are the primary causes and remedies for power transformer hum? I find that mechanical hum is particularly offensive. And no this is not a Transcendent Sound problem. I just figured that Bruce or another of you sharp guys could explain the phenomena. Thanks.

the gorn
Reply with quote  #2 

Hi Steve,   I found this article pretty clear.


   Is the transformer in question a toroid?

Steve f
Reply with quote  #3 
No it isn't. Interesting side note; putting something heavy on top of the amp quiets it down. If I leave the cover off, it still makes noise. I checked all bolts, etc and can't find anything obviously loose.

Reply with quote  #4 
Physical transformer hum or buzz can be caused by the presence of DC on an home mains line.  The DC causes an "asymmetry" in the transformer voltage that can saturate the core and produce vibration of the transformer.  PS audio at one point in time made a stand-alone product called "humbuster" to address this problem.
steve f
Reply with quote  #5 
That raises a follow up question. Why does this happen with only one amp? No other devices share the problem.

Reply with quote  #6 
Laminations on the power transformer can sometimes loosen over time, and so lead to possible mechanical noise and hum. The machine screws, of which there are usually four, can be retightened to snug them back down. Sometimes this can help fix or at least improve the situation -- not always, I've found. Some PTs seem to be more prone than others. I have had brand new transformers with mechanicsl hum, even with well-tightened screws. I have sent them back and received replacements that were fine.
Reply with quote  #7 
Steve:  The DC problem does not affect all transformers in the same way.  I had a huge toroidal in a balanced power supply "converter" (unbalanced AC mains to balanced AC out) that was fine for the longest time and then started to physically hum (very loud).  Never found out why for sure, but the local elec co had replaced a street pole transformer a 1/2 block away around the same time that the hum started.  This did not affect my T-8 or any other electronic component in the system.
steve f
Reply with quote  #8 
Thanks for all of your input guys. I gave up and traded it off to a buddy who actually wants to try and solve the problem. I wish him luck.

Reply with quote  #9 
I'ts really simple, about why the transformer hums.  It doesn't know the words.  
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