Whats the best and quietest 12AX7 tube

I agree with Opus88. The EI 12Ax7 is a very fine tube and can even compare equally or favorably to a Telefunken 12Ax7.

The best 12AX7/ECC83 is without doubt, the BRIMAR. Period.

I like old Telefunkens with the diamond bottom. The Tesla or EI (basically new telefunken flat plates-factory was blown up by Nato last year) are nice too, for new tubes. In my opinion the Sovteks are dark, too high in gain and boring. The telefunkens seem to be the most balanced across the frequency range and let the music shine-rather than displaying frequency aberrations

The best AND quietest us Telefunfen 12Ax7 smooth plate. I tried philips,mullard,rca,ge,brimar,torvac,mazda,amperex(german,american and dutch).There may be a few that I forgot to mention.The telefunken is also silent in a pre-preamp.Do not substitue a 12Ax7 with a 12AT7 or 12AU7.The gain charecteristics are different and might cause the phono section to ascillate.

Telefunkens are great, but I recently replaced my stock 12AX7 with a Heintz & Kaufman Gammatron, made in the USA. Just great. Fast and almost as musical as Tele's. Application will dictate, so experiment.