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

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?

Vintage RCA (Black & Gray plates) do have extended HF's for a 12ax7, IMO (more than the Telefunken and Mullard's I've used).

Old production Holland 12ax7's do also, but they are really expensive now.

Old production Sylvania 12ax7's have gobs of HF, but they are lacking the mid's and LF's that you like.

You might try a new tested pair of the Russian EF86's (old production winged C/SED are still available for $40/pr) in the event that yours have lost some HF extension.

Old production EF86's are also currently super expensive.

Remembered I used the EF86's in a couple of guitar amps that I was retubing for a neighbor for which I pulled a Telefunken EF86 from an old Pilot pre/tuner (don't really know how they sound in HiFi gear).

You might check prices on RCA 12ax7's (I'd look for new testing old organ stock to save money as the Baldwin (Conn?) labeled tubes were supposedly thoroughly screened for their intended purpose).

Not familiar with new production 12ax7's.

Oh, and here is a blurb I placed on favorites and forgot to include in my previous post.

https://www.audioshark.org//pre-amps-9/wolze-triode-line-level-preamp-4421.html

DeKay

DeKay

... thanks again Bud... Be Well, Best Wishes. Bill