NOS tube alternatives for Herron VTSP 3A r02


Looking for advice from actual Herron preamp owners who have experimented with different tubes. Recently acquired Herron  VTSP 3A r02 to be used with CAT JL5 amp. Speakers are Dynaudio C4s & ATC SCM19v2s.

I´m fully aware that manufacturer advises against tube rolling citing preamp was voiced with especially screened & selected modern tubes but I´ve decided to disregard for the following reasons:

Unit was purchased used & came with new tubes that are not originally from Herron & IM(not so humble)O & experience current production Russian and Chinese are vastly inferior in tone & timbre to NOS Telefunkens, Siemens and Amperex in relation to 6922 variants.

Thanks 


rost
Thanks for your input jmolsberg .
Coinincidentally it is precisley the Dutch  E188CC / 7308 Amperex I´m most incinled to try. Will most likely contact Herron for a set of theirs and compare. Should Herrons prove superior can always  use the NOS in other components.
Since there are 6 of them in the VTSP I´m wondering if I´ll need a matched sextet or 1 matched quartet + 1 matched pair or 3 matched pairs.
Keith told me he goes through something like 10 tubes that don't make the cut for each one he uses. This is after having selected the best tube type. This is just comparing the same tubes for quality and matching. He told me he has a barrel full of rejects. Which people are always asking to buy, because even some of his rejects are better than 95% of what they would otherwise get just rolling the dice on the market.

Which come to think of it, is what it should be called. Not tube rolling. Rolling the dice.

Or just buy tubes from Keith. 

(The more you talk to Keith the more amazed you are at what a stone bargain his stuff is. As if the sound alone wasn't enough...)
Do what Keith says and tweak something else in your system if you need to scratch that itch.
Buy the "NOS" and the Herron set, as you outlined above, and listen and compare. It'll be fun and it's what you need to do. 
     After 6 months of listening with the stock EH tubes, switched in 2 Siemens  Cca and 4 Philips E188cc ( didn´t have 6 of a kind) and the results were purely positive.

     Totally gone was any hint of electronic haze or the glare & brightness in the upper mids I find so offensive and characteristic with Russian & Chinese current production. Voices, especially female much more natural, soundstage opened up and best of all zero listening fatigue over very extended periods. Plainly, just much more musical.

     Advice about not messing with stock tubes from manufacturer and other content users seemed mainly based upon the argument that the preamp was voiced with provided tubes but it´s obvious that my setup ( Air Tight PC1s, SME IV, Avid Volvere, Zanden 1200 mkII, Reimyo CDP 777, CAT JL5, ATC SCM19v2, Audience SX & Harmonix speaker & interconnects, Cardas Golden Reference & Clear Beyond power) cannot be the same @ Herrons or any other where this particular piece is used.

     Anyway, cheers and remember YMMV.