What is your favorite tube for a preamplifier ?

Orpheus. Why is the RCA 12au7 your favorite? My Rogue Cronus takes a 12au7 and I'm currently using the Sylvania that came with the amp.

Ecclectique, you are correct, I forgot to mention that 6J5 has only one triode as opposed to two triodes in a 6SN7.

I wonder if you have found a military equivalent of the 6SL7, similar to your favorite 7193 in place of a 6SN7 ?
Best wishes for 2010

The NOS RCA 12au7 made a gigantic difference in my CJ PV10 and PV12. It is also less expensive than the other NOS tubes.

I used very expensive mullard NOS 6922's in my Audible Illusions M3A and got only a small improvement, but that could be because the M3A is so good that it is hard to improve.

Well, one of my favourite preamps (Atma-sphere) uses 6sn7s, but my other favourite tube preamp (Joule) uses 6350s which I never heard of - I think they were designed for TVs, not sure, but it sure does make for a nice sound preamp. My other tube preamps have used 6922s and/or 12AX7s. The old ARC SP6 used all 12ax7s I think, and for the time it was a might fine sounding preamp.