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Transformer Noise

I have an old Krell KAV-2250 that sounds pretty nice, except for the transformer hum.  The hum is noticeable when the volume is at zero and slightly audible at lower levels.  The amp has been unplugged for a few years.  Is there anything I can do to eliminate the hum or does that just something I have to live with due to the high power transformer?  I was going to send this to my son, but I think it might really bug him (it's bugging me too!)
thegoldengoose
erik_squires
15,803 posts
 
If it's mechanical, it may indicate you have DC on the line, often caused by light dimmers or PC power supplies.

If it's coming through the speakers, check out my blog page:

http://pqltd.blogspot.com/2016/11/quick-safe-and-easy-fixes-for-ground.html
thegoldengoose OP
16 posts
 
Erik, you are magic! I unplugged a small transformer that was next to where my amp was plugged in and the noise stopped immediately. The offender was a small "wall wart" that charges my Chord DAC.

I had another amp plugged into the same location (with a different power cord) and I didn't have that problem.

Thanks for this post & all your other posts!
gs5556
1,213 posts
 
That is also a symptom of a filter cap gone bad. Try using a cheater plug -- if the hum is reduced it's most likely ground loop, If it stays the same, probably a capacitor. 
erik_squires
15,803 posts
 
Most welcome!

Erik
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