2. amps-preamps
  3. 1270085894

Noise at start-up of one mono-block

I have a pair of Quick-Silver mid-mono monoblocks. Over the past couple of days, each time I switch the left one on and after the tubes heat up, (about 5 to 10 minutes) the amp makes a loud buzzing sound.

If I switch the amp off and on again then the buzz stops and does not come back until the amps has been shut-off over night.

Any ideas on what the problem could?

The amps are less than a year old.
The tubes are biased and the bias holds.
The noise occurs even if the pre-amp is off.

Is this the result of a faulty input or driver tube?
nick_sr
onemug
784 posts
 
Switch all the tubes from one monoblock to the other.
That should tell you if it's the amp or a tube then proceed from there.
rrog
1,958 posts
 
Call Quicksilver Audio and talk with Mike Sanders. He is a great guy. I am sure he will help you out.
nick_sr OP
263 posts
 
All very logical and obvious suggestions. Thanks!
nick_sr OP
263 posts
 
I switched the input and driver tubes on the amps. There was no noise at start-up but after about an hour listening the buzzing noise started again in the left amp.

So the input and driver tubes are ruled out as the problem. Once the amps cool, I will swap the driver tubes.
nick_sr OP
263 posts
 
Swapped the output tubes (not the driver tubes) and the buzzing moved from the left to right side.

Conclusion, faulty or worn output tubes (EL34s).

Now, I have to replace the pair for a new matched pair. Should I replace the output tubes on both amps?
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