Before you start replacing tubes, I suggest you pull the tube(s) and clean the contacts. I had a similar experience with a Brimar NOS 12AU7. It was so bad that walking around the room triggered noise. But after using high quality contact cleaner and spending some time wigging the tub in its position all is working good again.
I have an odd problem with microphony...
Occasionally my system makes a hum that sounds almost like a musical note. Two days ago it started up and, as usual, when I switched the source switch it stopped but would start up again if I tapped the preamp or the phono pre. It seems to react more strongly to the pre than the phono but I will also hear a similar sound if I tap the TT. The most odd aspect is that yesterday I played the same record and there was no sign of this hum. I have a Lamm LP2 Deluxe and a Lamm LL2 Deluxe, both tube amps, and I recently added Herbie's Tube Dampers to try to cure the problem. Any ideas out there?