Microphonic tubes...

I have noticed that two of the 4 6GK5's in my CJ Premier 10 preamp are somewhat microphonic, producing an occasional high freq whine. I can tell by lightly tapping them lightly with my fingernail. One recently went bad, so I replaced it with a spare I had laying around. System sounds ok - no whine anymore, but I think the tubes are rather old, and I am going to go ahead an replace them all, how do I go about selecting a non microphonic tube with good sound. I can get a set of 5 NOS tubes of either GE or Mullard for cheap - $15.00. Any inputs, other suggestions on which tube might be better from any tube masters out there would be very much appreciated...Tim
audio research sells tube dampers - at ~$5 a whack, it mite be worthwhile checking out....
there are some black rubber rings already on the tubes. I asssume they are tube dampers that you refer to. They don't seem to make a marked difference in the microphonics of these tubes, at least as far as I can tell. I thought that would be the solution too, but when I took off the cover, those guys were already on the tubes! Are some brands less microphonic than others as a rule? thanks again for your response
Being new to tube equipment myself, I've researched this issue. It seems that there is quite a bit of variablity from tube to tube as far as microphonics and noise. Especially among certain nos tubes. It would be woth your time to go to www.vintagetubeservices.com and read what Andy has to say about these matters. He tests his tubes for these problem areas and grades them accordingly.
i'm w/photon46. my toob experience is wery limited - only w/preamps w/the 6sn7 toob, & the 6922. i found the 6sn7 to be a lot more microphonic than the 692 regardless of which mfr, & i had 3 different types of 6sn7 & 3 different types of 6922... not familiar w/the 6gk5, but andy at vintage tube services is good. i also like bruce wenger at www.bws-tube.com

good luck, doug

I think part of the problem may be that the 6GK5, although nice sounding, is an inconsistant tube in terms of microphonics. The good news is that they are cheap, So i can afford to go through a few to find the good ones.