The only tube mic I own says Protube on the front. I bought it used in the nineties. It uses EC92 tube, and I found them easily on the web. I slid off the enclosing metal "tube" to reveal the insides, swapped the tube in the socket and was a bit disapointed that I didn't hear much difference. Really very easy.
I remember being adviced not to touch the tube glass, as that would leave marks that might shorten its life.
Off topic: I don't know anything about this mic except it was part of a stereo set. The external power supply that I have has two connections. I find nothing on the web. I suspect it might be a sixties eastern european design, but I don't know. It sounds ok, but I never really explored its potential. Any info would be great. Putting it out there just in case any one has any info, or else ignore this.
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