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
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?
rrog
1,958 posts
 
I would replace the output tubes in both amps. With fresh output tubes in both amplifiers you should get a powerful balanced sound.

Also,I recommend ordering the tubes from Quicksilver. They know best when it comes to sorting and matching tubes for their products.
nick_sr OP
263 posts
 
Thanks Rrog for the advice.

If I am going to change all the tubes I was considering changing from EL34 to KT88.

Do you, or any one else have any experience with running the Mid-monos with KT88s.
rrog
1,958 posts
 
I was going to recommend trying KT88s in your amp. I don't have experience with your amplifiers, but I have owned other Quicksilver amplifiers with KT88 tubes and the sound was very good.
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