... How to select tubes for line level preamp ...

The 12ax7 has approx. 5 times the gain of a 12au7 "type" tube. 

Never seen/heard you preamp but, from what I recall about it an unusual 12au7 type was used.

I may have run  across the Wolze when researching tubes for my "early" Bottlehead Foreplay 12au7 based preamp years ago, but I do not recall the specifics (certain that it was not a 12ax7 though).

I'll try searching the old Bottlehead forums tomorrow to see if I can come up with the 12au7 equivalent that I researched (like 15 years ago;-)

This said, if it has been changed/modded this will be a mute point.

I've rolled the 86 tubes in something (thinking a vintage Pilot 690 preamp/tuner), but again I do not recall specifics as this was a long time ago.

Anyway, if it does end up using a 12au7 I'm familiar with gobs of old production types and can chime in @ that point.

DeKay  

DeKay

Thanks for the courtesy of your reply... 

insearchof, The most important characteristic of a tube is noise. There is a lot of variability between tubes even of the same manufacturer. Noisier tubes decrease dynamic range and can interfere with quiet passages.
RAM Labs tests their tubes individually and rates them as standard, low noise and super low noise. They are priced accordingly. I use their SLN tubes in my ARC phono amp and they are an easy 10 dB quieter than the tubes that came with the unit.  http://www.tubeaudiostore.com/

Couldn't come up with much other than a few references to 12au7 and 6211 tubes in the Wolze (along with EF86).

These came from title headings on Google, but the articles/pages were no longer available.

6211 must have been the tube I researched for the BH preamp.

Some hits to VTV magazine that I did not look at (reading VTV gives me a headache).

I understand that these were kits so anything is possible considering Wolze and the wild and crazy guys/people who most likely built them.

What 12ax7's are you currently using?

DeKay

DeKay

These came with the unit when I bought it...

This is the info printed on the tubes: (2 of each)

(In silver lettering): USA, above 12AX7A (in a thin silver oval)
                                  RCA (in gold lettering), else where on the tube
                                  Other info on tube worn so it can't be interpreted

(in gold lettering): EF86 6J32P Made in Russia
                                 SVETLANA

AND You think /suggest?