6bq5 is correct, to my knowledge, about the Ei's. They used to come stock with Jadis preamps before the war came. I have a set that came with my JP80 and a spare reserve set, but they're in storage since I started using Telefunkens, which are just plain a world better and much more long-lasting. Tonally, the Ei's were similar in some respects to the Telefunkens, maybe a shade warmer, but not nearly as dynamic or resolving. I have also used Teslas (12AU7s) in my Audio Logic DAC; they have a warmer, less bright sound than the stock Mullards (probably Brimars?) that AL likes to use. Again, I replaced them with Telefunkens, and the Teslas are back in the drawer for good. Teslas sounded OK, but dark compared to the more balanced (in my system) Telefunkens. The Teslas didn't last particularly long, either, compared to the Teles, which I believe is a common complaint about most all of the tubes made after the 60s.
Any other tubes out there?
I always see ads for mullard,amperex,and telefunken tubes. Now I am sure each have there merit, but I was wondering if anybody has listened to other nos tubes like Ei,telsa,rft,mazda. I don't see these for sale as much as the ones mentioned. Anyone out there care to shed there input? Thanks Bret