What is your impression of vintage Telefunken signal tubes ?

My Linear Tube Audio MicroZOTL preamp uses 12AT7 input tubes.  My favorite is the Telefunken ECC801S.  Second place is a Siemens ECC801S.  I've tried several other tubes that sound pretty good, but those are my favorites. Very detailed, but not overly bright or harsh in my system. 

Without getting into some esoteric tubes that may better them, Telefunken are simply the best if you like clear and transparent sound. 

Everyone likes clear and transparent sound but there are other elements of realism that are no less important.

Of course there is no one perfect tube and one type of sound is inherently different from another.  Telefunkens deliver clarity and explosive dynamics but that makes them lean sounding (lacking in warmth).  For the 12 AX7 type, I like the Telefunken ECC 803S which is a bit lean and bright, but it otherwise great sounding.  I run these in my phono stage.  Sadly, they are quite crazy expensive.

Only tube I roll in the Lamm ML2-- the 12ax7. I prefer the ribbed plate only because the smooth does not have the same "grit" and the amps don't need more "smooth"---I have a good stash of these old tubes, NIB/NOS.