Alo do a search on the Asylum Tube section for posts from Bambi B. A lot of great firsthand use info on the 12AT7 variants.
Telefunken Tube Information Sources?
Can those who are deep into vacuum tubes direct me to the best (The best Jerry, the best) sources of information on small signal Telefunken tubes, particularly the 12AX7 and 12AT7? I see them priced from reasonable to VERY expensive, and I don't even know the desirability of the ribbed vs. smooth plate versions. I gotta finally educate myself!