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Hi all;
I'm rather new to tube equipment and high-end in general. This problem deals with the tubes on our TP 2.0n preamp.
The other night when listening, I noticed an unusual noise coming from the left speaker. We had just shaken the room with Micky Hart's Dafos album... serious bass on The Beam.
The noise was a cyclical, tinny, almost motor-like sound that would repeat in a 1-2-3 pattern. It was very noticeable from the listening position - enough to interrupt the session. Interestingly, it had the same tone or pitch as the microphonics that I *sometimes* hear on the pre-amp... if I tap the volume knob, I get that ringing sound. I turned off the TP 2.0 for a minute or two, re-started, and the sound was no longer there.
Just for gits and shiggles, I later rolled the tubes over one position. 1 went to position 2, 2 to 3, ..., 4 to position 1. I ensured that they were well seated, and then reinstalled Herbie's Tube Dampers a bit higher up - about as high up the tube as I could get them.
When I went to play again, at idle the preamp was dead silent. No microphonics - which continues to be the case - no recurrence of the cyclical noise.
So, the questions are: What's going on with the tubes? What might I have done to correct the problem - was it reseating, or repositioning? Do I have a tube going bad? If a bad tube were in, say, position 1 and then moved to position 2, am I going to be missing or risking something?
The tubes in question are Amperex PQ white label 6922s.
Thanks! I have no doubt that someone knows what's going on here.
Rob
