Question for tube aficionados

I have a VTL 2.5 preamp
I ran OEM 12AU7 JJ’s up until about 4 years ago.
I went to NOS 12AU7 Amperex Bugle boys - a significant improvement over the JJ’s
I just got NOS Telefunken 12AU7’s - another significant improvement over the Bugle Boys. There’s a new level of openness

I asked CJ what the tubes were, and surprisingly the reply was  the 12AX7 Mullards are NOS, the others are new production.
The question then becomes, which Mullards are included?

One word “ TELEFUNKEN “! I have NOS 12AU7’s ( E82CC, ECC82) in Telefunken , Tesla, Seimens , Mullard , RCA, Tungsram . They all are better than new stuff . They have distinct tonal differences . I use 5 different NOS rectifier tubes which raise or lower the voltage and effect my power tubes . So driver and rectifier tubes are all NOS. They last a long time . Power tubes - I have NOS GEC KT88 and KT66 , NOS Tungsol 6550 ( 3 hole ) , and SED Winged C 6550 and 6L6GC. They are better than current production tubes and more expensive. New production, I have Gold Lion KT88 and KT77 ( very nice sound ), Psvane TI KT88, Tungsol KT120, JJ KT77. Of the new stuff I am fond of the GL tubes . But for your application Telefunken NOS. FYI Brent Jesse’s site gives a very accurate description of SOUND from various tubes . FWIW, I have $3k in tubes for a $1500. Amp , so you see where this can take you 😝. Shoot me a message if you have specific questions . Happy Listening , Mike B. 

I recently upgrade my Cary 120 with new Gold Lion KT-88's and Psvane 6sn7.
Previously I had Gold Lions, but they had quite a few hours on them. I also had Tunsol 6sn7's
The Psvane Grey bottle are a matched Quad and the Gold Lions are a matched octet.
I'm constantly blown away by the increase in soundstage and detail, both high and low.
Psvane makes both a 12au7 and 12ax7.

I will be upgrading my Cary SL98P F1 from the Tunsol 6sn7 to a Psvane grey bottle matched quad.
I like the Psvance, that much.

The difference in sound between NOS and new production tubes is slight and you will spend a lot of money finding NOS tubes that are (1) not fake, (2) not microphonic (3) not noisy. My 2c worth. I gave up the chase years ago and now use matched and tested JJ or Sovtek tubes.

Also, CJ amps of this vintage typically use circuit designs that are not optimal to produce a "tubey" sound. They are also prone to oscillation with the wrong tube choices because of CJ's refusal to follow good design practice and use grid stopper resistors. The difference NOS tubes will make is like cables - not much. I'd stick with what works.