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

Buy vintage EF86's and 12AX7's! Avoid present day tubes! That tube "magic" existed in decades past - not so much today! And the old production tubes will last longer in use!

Was you preamp modified?

The original Wolze used a 12au7 "type" along with EF86.

DeKay

DeKay

Did you /do you have one of these - it’s been "rumored" there was less than 10 ever available: any opinion /review from your memory?

If you can explain please what is the differrence between a 12au7 and
a 12ax7 (other than having this one Wolze piece - I have no reference to tubes what so ever).

Thanks...

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...