I am using the RCA and Sylvania 5751 NOS tubes in my Aesthetix Calypso pre amp replacing Mullard and Telefunken 12ax7 tubes, quite an improvement in my opinion. Three things to condsider, can you phono pre use 5751 tubes, 5751's provide about 70% of the power of 12ax7, need high quality to avoid microphonics. Good luck.
What are some favorite NOS 12AX7s for phono?
I recently bought a new phonostage here on Audiogon. I wanted something made right here in the States like my last tube preamp,so I pulled the trigger on one made by Jenison Audio;the Perpetuum model. I checked and he(seller: dividebytube) doesn't have one listed for sale right now, but I have been really happy with it. I have a VPI table w/ SME 309 arm, and right now I'm running a Dynavector 10X5 high opt. MC phono cart. I have tried Sovtek LPS 12AX7 tubes and liked the treble detail and "crisp and clean" sound they offer, but I am definitely looking for more of a 3-D sound. I am open to suggestions for NOS (or modern production) 12AX7 tubes that balance detail and warmth, sort of an "updated vintage" sound. I welcome any suggestions.