I've been having some pretty severe microphony issues with my 3.1a preamp of late. My assumption was, of course, the tubes. At Dennis's suggestion, I tried some 6dn7 instead of 6sn7; they sounded great in fact, and were cheap. So when I started to get the very fine, pinging and ringing sounds I assumed the cheap 6d's were at fault, so plugged in my trusty old Sylvania 6sn7...only to find that, after a period of warm up, the high pitched pinging and ringing returned.
I also have 6922/6dj8 in my phono stage, another tube that is prone to microphony, but I'm pretty sure I can trace it to the 3.1a preamp.
Has anyone ever experimented with rolling the 6bx7?
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