vintageHIWATTconvention.com

I have a Dr201, el34 version. I had suspected that a preamp tube had become microphonic to the point of ringing out. I identified the V1 tube and swapped it out. The new tube in V1 was ringing. Then to confirm the tubes issue i put the old 'suspect' tube in v2 were it was nice and quiet.

So, I am left with a V1 socket that is adding some of its own noise. I realize that all tubes are microphonic to an extent, but this one caught my attention when I tapped the faceplate and it sounded like I was inside a glass bottle. Cool, but not helpful.

My question to you fine folks is... what do I look for? This is a new issue to me.

A shout out and thanks to Hi-Tone for some new chassis screws that will be used once, I address this issue.

is the socket secured firmly to the chassis?

are all of the wires soldered in the lugs securely?

Does the tube fit snugly in the socket? You may need to try to tighten up the contacts in the socket. or worst case replace the socket.

As you mentioned, 12AX7s are inherently microphonic. Many times I find new ones as bad as the ones I'm replacing in this regard. The only thing to do sometimes is to try a few different tubes and find a quiet one. The high gain amp guys really struggle with this.

--mark