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.
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
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