Most Musical 6NS7 tube for a Preamp?

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

Get a 6f8g and an adapter. It’ll blow your mind 

Having tried the top thirteen tubes, of this comparison: http://www.dehavillandhifi.com/6sn7_vt.htm, I have to agree, the Tung-Sol, round plate, w/oval mica, is a beautiful, neutral, extended at both ends, with excellent sound stage and precise imaging, tube.      The pair that I now have in my Carys, came out of three NOS pairs (from three different sources), however.     The other four all went intermittently noisy(crackles), after less than a year, each.      However; I’ll never regret the purchases.      They’re that good.      As some surveys mention; It’s good to mix tube iterations, even if the same brand, which retains the strengths of both, while not emphasizing any weaknesses.      I’ve tried everything mentioned (the top thirteen), in various combinations.     In combo, with the T-S, the best were the tall bottle, metal or black based, Sylvania 6SN7W and Ken-Rad (bottom-gettered), from the 40’s and this Sylvania: https://tubeworldexpress.com/products/vt-231-jan-chs-6sn7gt-sylvania-1944-v1?_pos=1&_sid=79a7fa3be&_ss=r, which gives me the best mid-Bass slam, without coloring the Midrange.      Those four tubes, in whatever position, offer the best sound stage, in width and depth, of any tried, in my system, not to mention, REALISM (ie: tone, dynamics, etc).      I’m staying stocked up, on the others, for when I’m out of (or can’t afford) round plates.      If by, "musical", you mean a warm, tubey, sound; try the other top tubes, on the above mentioned survey.      They all have good presentation, but- were a bit too warm, for my taste.      More opinions, which (of course) vary, per system/ear:   https://www.head-fi.org/threads/the-reference-6sn7-thread.117677/    and:  http://digitalaudiodirections.blogspot.com/2012/06/6sn7-tube-comparison-part-1.html   Enjoy your journey!

Try some old Red Base RCA 5692 - the very best 6SN7 there ever was. The go for about $100 on average 

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F174260219898

These are what your looking for  - just as an example - no affiliation with seller - proceed with the usual caution 

Good Listening
Peter