Well, I've reached a point where the noise in my Inspire 3.1 preamp is unacceptable. Something is clearly amiss. There is a very high buzzing or "tinkling" sound that does not sound like normal tube microphony, which I've heard a zillion times. It comes and goes, which is puzzling.
I do note that in this preamp application the 6sn7 is incredibly microphonic, whereas it's never been a particularly troublesome tube for me in the past, going all the way back to my Conrad Johnson MV60SE that I had a bunch of years ago, and is currently the first stage of amplification in my Radio Craftsmen RC2's (which are wonderful and overlooked amps, especially if the first stage of the 6j5 is taken out of the circuit as I've done).
I've tried scads if different tubes in all positions in the 3.1 except for the driver 6bx7, so that may be the culprit...
In any case, Dennis has not answered my last three or four emails, so I'm coming to this forum, and to Straitwire in hopes of directing attention towards my queries. The preamp sounds wonderful, very forward and alive, definitely a "first row" presentation, none of this middle of the hall baloney, and I'm happy to ship the preamp to Dennis if, in fact, there might be an issue.
I could just buy a new 6bx7, but there's something that tells me we might have a more serious problem.
Many thanks, Straitwire. I know DH is awful busy making the world a better place through his excellent designs--my life has been better since purchasing the 3.1 and Inspire FireBottle, two pieces I will never part with--so I'm looking forward to getting to the bottom of this.
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