Tube recommendation for Audio Research LS-2b?

Yes a large '253' is etched vertically near the top. The orange labeling is easily scratched off, however.

The 7308 is the top of the line tube in that category. The Amperex is an excellent tube. Very low noise. Provided it is a legit Amperex. It should have a number etched in the tube I believe.

I have an LS2B-MKII and have compared the stock Sovtek 6922 with an Amperex 7803 (PQ/Orange). The Amperex was much more detailed but added a slight sibilance. I'm not sure if the tube was the issue or whether the preamp needed a bias adjustment. (the seller said the tube was NOS and tested well).

I had the LS2 a number of years ago, and it definitely needed the warmth and slightly softened highs provided by Amperex Bugle Boys. The BB tubes were also very dynamic. In contrast the tubes I bought from ARC, a Chinese 6DJ8 and a Sovtek 6922, were coarse, grainy and lacking in refinement.

I own also a ls22 and i measured that my EI ecc88 have a fillament
current togheter of 1.6A[incl.relay circuit].that is already to high for 1.5A max.LM317!For example a 7308 have more current than that.

I had an LS 2b. Have a LS 5b as a backup pre

You really need warm tubes for the LS2

nos telefunkens,mullards and amperex from the sixties worked like a charm for me

I switched my LS2B to a Mullard Gold Pin and it sounded great.

The Chinese 6DJ8 drew a bit more heater current then the standard Russian 6922 if my memory serves me. So a different value resistor was used for the Chinese tube. The Chinese tube was stock at the time that preamp was manufactured.

I have a ARC LS22 that I use sometime and use to use the LS2B. If you want a nice improvement and not spend big, try these. They work very nicely in the ARC gear.

http://www.tubemonger.com/Matsushita_Japan_6922_E88CC_Mullard_Tooling_NOS_p/591.htm

These are also very nice sounding in my ARC gear.
http://www.tubemonger.com/Tungsram_E88CC_6922_MINT_NOS_NOV_1973_HUNGARY_p/1108.htm

If you don't mind spending a little money.

http://www.tubemonger.com/Mullard_MPs_MINT_NOS_1967_MIL_7308_CV4109_E188CC_B_p/2000mb.htm

I also like the Amprex 7308's but they also are quite expensive now.

Sovtek 6922 as the original tube in your LS-2 did not sound right to me, so I did a little research and as I suspected the original tube was a Chinese 6DJ8. As I recall it was actually a 6DJ8H. My favorite tube in the Audio Research hybrid preamps back then was a 6DJ8H from Penta Labs. I recall Audio Research explaining the preamp is biased for that specific tube and in order to properly use a different type of 6DJ8/6922 a bias adjustment is required. Without the correct tube or the proper bias adjustments the sound would become dull. Bias is adjusted by changing resistors to achieve the proper settings.

Try a Amperex Orange Globe, I always keep going back to them and they are affordable, if you wanna spluge a Telefunken 6922. I have a bunch of OG's A frame Dimple disc and O getters, $20 lemme know if you want 1.

I'm sure Audio Research would have the best recommendation for you.