help me select a single tube to "calm down" a preamp?

Personaly I've had a tough time rolling tubes in my ARC LS-15. While there are a lot of good/great NOS tubes that will do the job, I find it difficult to get good examples. I still keep going back to the stock tubes. While ARC does charge a premium for their tubes, they are matched and tested. They have performed the best for me so far. At least you only have one tube to deal with. Maybe you should start with a fresh tube from ARC? Then you'll have an accurate bench mark for comparisons. Good luck....

Mejames suggestion of the Telefunken echo my first or second choice as well. Be aware that the correct number for the Telefunken version of this tube is 6DJ8. The 6922 Tele is not only extremely rare, it does not have the sonic signature to solve your problem.

Another high on my list is the gold pin Mullard 6922. Just be sure its the British version, not one manufactured in another country with the Mullard logo.

It is sometime necessary to attack this type of problem from two angles. If you list the other tubes in this unit, I will suggest replacements that work with the 6922 and bring you closer to the tonal balance and resolution you are seeking.

Go and buy yourself an Amperex Bugle Boy 6DJ8 and all your problem will be solve.

I second the vote for the bugle boy 6dj8
I believe this tube best describes the
sound you are looking for.Although i will
say,telefunkens are the best tubes ever built.

3rd on the vote for the Bugle Boy. Just be careful of "fakes".