It looks like the microphonics are often associated with the power tube. In my Crack, I tried three different 6AS7G (RCA, Svetlana and Rogers), all were noisy, even after some break in. I finally settle back to a rugged RCA 6080 with RCA or Telefunken 12AU7. I can dance next the crack (which happens so often with the hd650), no ringing!
Edited by ffivaz - 3/24/14 at 1:08pm