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
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.
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.
I picked up a matched quad of electro-harmonix KT88's from my dealer who sold me the amps. There not from Quicksilver but I had to make a choice, no music for the long Easter week-end or wait for Quicksilver tubes. The choice was clear.

I haven't had a chance to have proper listen and the tubes probably need to burn in a bit before I come to any conclusions. Based on my first impression, the sound is much different, drums and bass are more pronounced but with less warmth.

Thanks for the input.
I am not familiar with EH KT88s. They may need a little burn-in time to sound their best.

Quicksilver has been selling Chinese KT88s for years. They sound very good. In fact I was considering Gold Lion reissues for my Dynaco MKIIIs, but all recommendations were for Shuguang Chinese KT88s.

Let us know how it goes with the EH tubes.