What is your impression of vintage Telefunken signal tubes ?

I just purchased a pair of 'expensive' 12AX7 tubes for my Zesto preamp. 

During my phone call with the seller, who is very well known and respected, he advised me to not purchase Telefunken because they would sound too dry in my system.

This is not personal experience, but everyone here trusts his advice.  YMMV.

It almost sounds like they are kind of 'military' tubes, nothing to do with art. No one mentioned great midrange and soundstage. 

I’ve used the vintage ECC83’s in all my tube amps over the years and they are by far the best I’ve ever used. Fantastic detail and decay, great soundstage, etc. 

They're my go-to when possible. 

telefunken small signal tubes (real ones from back in the day, not the modern branded tele’s) are excellent, though they are in the clear and precise school of sound with excellent air and imaging, not very overty tubey in their sonic nature

to me they are not better than other top european tubes from that era, mazda’s adzam’s siemens cifte’s dutch amperex and even hungarian tungsrams

somehow the tele’s became ’legendary’ and demand for them went off the charts... made them poor values to buy, even in the 80’s and 90’s

If Brent has Telefunken 12AU7s trust his recommendation.

I've used Sylvania, vintage RCA, and vintage Tungsol 12AU7s in a Rogue linestage over some 20 years, each with an improvement in clarity and quiet background, respectively. The Telefunken blue tip medical application tubes from Brent are the best for clarity, quiet background and dynamics. They are not warm but neither are they cold or bright. Their $850 price is offset by the fact they should last ten thousand hours. The system was upgraded from two way speakers and 40WPC amplification to Sasha II's and a VAC 202 stereo amplifier. The Telefunkens do a great job of providing a straight wire with gain performance. Of course this is subjective but I'd put faith in Brent's opinion.