Most Musical 6NS7 tube for a Preamp?

Thank you gentlemen for the education and experienced commentary.
This is why I enjoy Audiogon. 

I am trying to learn about 6SN7 tubes and even though I erred in the Subject line as 6NS7 no one felt the need to mention it. 

I am also shopping for a preamp to go with the Pass XA25 that is
supposed to arrive Friday. Input Impedance 47k.

Must haves include:
-Remote
-6SN7 tube
-Most musicality/$

Must not have:
-the words "headphone" or "schiit" attached
-over 5 years old and one owner.

A true bonus:
-trial period

Preamps I have recently owned:
-Audible Illusions L3A-Only dislike was the sound
with or without it seemed the same. Shouldn't a
preamp improve the sound or is that a myth?
 

Brands of Intrigue that fit my $3k budget:

-Supratek
-LTA
-deHavilland
-Audio Note-(likely too high even used)

Thank you again for sharing your knowledge 
and providing me excellent guidance.

@atmasphere 8,170 posts04-29-2020 9:00am
...

The best sounding 6SN7s of current production are coming out of China. We’ve seen fairly short lives out of the Sophia tubes, but otherwise the Chinese boutique 6SN7s seem to hold up well. I would stay away from the Russian fare unless you are able to find 1960s-era Soviet 6SN7s which are excellent. ...

Yep, agree. Was hard to believe, but true on my end too. The past two years of CN tubes are improving for sure. After restocking up on vintage RCAs, Sylvanias, others, and recent TS re-issues - compared again recently. The new CN stuff is inching closer now. PSVANE acquired all tooling/methods from TJ Full Music [small tubes] after the old man passed. Now with the reported Shuguang fire last year, will be interesting to track new developments this year on 6SN7s, other 12Ax,t,u,7 tubes too. Re-trying some small CN PSVANE "T-Treasure MKII" version input tubes now, made in 2020, better than 2012-2016 versions I tried before. So what’s changed...hmmm. Kinda getting closer to my mid-1960s Blackburn Mullards, maybe improved in some ways too with midrange and wider soundstage. Maybe a tad less texture, more burn-in required. Was not expecting that. Re-evaluating periodically to check my own hearing or wondering if I was imagining it. Nope, not imagining it, inching closer :)
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Out of the 6SN7 preamps above in your price range the deHavilland would be an excellent choice once modified.  How do I know, I have repaired and modified most of them.  In the deHavilland a toridal transformer replaced the original, V-Capacitors were an upgrade and Audio Note resistors were an upgrade, and tube sockets, etc.  The 6SN7 tube was a cheap CBS which sounded the best in that preamp.  I think you can fit a nice remote volume in there if it does not come with one.

As for the 6SN7 tubes (the deHavilland only uses one 6SN7) the NOS Tung-Sol black glass round plates were the most musical I ever heard - don't agree with the tube chart link in one of the posts above.  Did not work as well in the deHavilland as in other preamps, Ken-Rads are very good, RCAs musical but soft sounding, CBS sound excellent especially as they are so cheap.Tried the CN CV-181 and with the correct bias setting they sounded very nice, pretty balanced top to bottom but overall not my favorite.  Tried the Treasure WE 101D tubes and preferred the Full Music much better versus what others have said about them in the past.

Happy Listening.

BK,

What do those upgrades approximately cost parts and labor?

Thanks for tube tips too.

Have you any first hand knowledge of the LTA or Supratek products?

I’m using the Tung-Sol black glass round plates in my Audio Note pre. They are so pleasing to the senses.

Some good info...
http://www.dehavillandhifi.com/6sn7_vt.htm