What is your impression of vintage Telefunken signal tubes ?

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.

I understand, Valvo tubes are very much like Telefunken, correct ?

@inna Re the ECC83/12AX7: Add in great sound-staging, imaging, fine detail retrieval, superb dynamics, an absence of grain or harshness and most importantly, flat frequency response. Ribbed plates are a little brighter while the smooth plates have a slightly smoother top end. 

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

Installed a pair of Siemens 12AU7WA in my preamp about 5 hours ago. And they sound liquid, 3D with a humongous wide sound stage. No experience with Telefunken - but have always read great reviews. I think a lot depends on system matching too?

noromance, I see.

I have a VAC Avatar SE integrated, it uses three 12AU7 in the driver stage. When I asked Kevin, the designer, he recommended Brimar and Sylvania, and that's what I put in it - Sylvania long black plates from 1950s.

I thought I might try at some point Telefunken/Siemens/Valvo.

I use 12AX7 Mullard long narrow plates from late 1950s for phono and line amps, and Mullard EL34 XF2 power tubes.

Everything sounds excellent, very balanced. No need to change anything, just audiophile curiosity.