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Tube Question--Slight Ringing coming from one side

I am running a pair of Klimo Monoblock amps, EL34 based. I baised them about 2 months ago, pretty much everything has remained the same except I had to move them closer together and closer to my turntable. Within the past 2 weeks, I have noticed out of the left monoblock a slight ringing (not really a ringing, but kind of like the sound of a refrigerator at idle) not at idle, but when the volume is turned up to a conversational listening level. it increases as the volume is raised

I have never experienced this before in this amp or any tube amp I've owned in 20 years. I thought of using a tube damper on the el34, but this is not addressing what may be a problem. Could it be the tubes are ageing? I was able to bias them exactly at factory specs 2 months ago.
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dc007
1 posts
 
Possibly a micophonic driver tube. Gently tap on the top of the driver tubes when it is playing and that should cause the offender to make a little more ringing. I doubt it is one of the EL34's. Not very familiar with the Klimo's
newbee
4,767 posts
 
I think Dc007 is correct, although I'm not sure I'd want to be tapping on a amp driver tube unless you are an experienced tapper. :-)

What I would recommend is doing a normal process of elimination. Just switch the driver tubes from one mono to the other and see if the noise follows the tube(s). If you have more than one small tube then reverse the process one tube at a time until the noise switches back. In so doing you would also be reseating all of the driver tubes and by doing so cleaning off any accumulated corrosion.

But, what ever works......
dogpile
118 posts
 

Try swapping tubes to isolate the culprit...left > right / right > left channels on both amp and/or pre amp. Eventually, you will find the microphonic tube.

Good luck!
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