Line Stage Preamplifiers AX vs AU

I was told that a 12BH7 can be used as a replacement for a 12AU7. Is that true?

I've read notes about this compare, So I boughta bunch of 12BH7's, and none stood up to Tele 12AU7 as far as sonics, sound stage etc.

As I mentioned above, there are slight differences between the two and while they will appear to sub each other, the simple fact is that they won't sound right if the circuit isn't optimized for them (if the two tubes were identical, then why it the 12BH7 taller and needing twice as much filament current?). So its no surprise that the 12AU7s sounded better in your case. But if the line state were optimized for the 12BH7 the tables may well be reversed.

The 12BH7’s are the driver tubes in my power amps. I am not using them in my preamp!

For me 6SN7 is the way to go. I had a PL preamp. Once I had a 6SN7-based pre it sounded so good in my system I bought another. 

^^ Yes- once you hear what they do its hard to go back to miniature tubes.

Yeah thing is, DIY folks can complain *yeah this jadis circuitry is all funky,, so many things I JUST DON"T GET,,,* 
I've heard this from both my  local New Orleans techs,, My Baton Rouge tech, doesn't seem to care .
anyway,, the local tech's mod of replacing the 12AX7 to a  12AU7, = did not work out.
The sound is mushy, = that *Jadis sound*  has departed.. 
so for <<all Jadis' faults > in designs, maybe they did actually know what they were doing...
Now i have to convince the  tech guy, that although he hada  great idea,, and on paper his idea was not so bad, I really need to hear what I know was there , pre mod.
My suggestion about mods, is don't go for it, Tweaks, yeah, upgrade a  cap, upgrade a  ressitor,, but don't change up the circuitry.
He is convinced his mod is superor to Jadis' orginal 12AX7 design.
Also everyone is saying the cd buffer on the DPL actually *adds distortion* = bypass and use the  AUX out,, Not to my eras, The 12AU7 buffer sounds superior to AUX.
Just wondering is there some sort of,, **ohh those french Jadis designers,, man just what are they thinking.>> Hangup attitudes among some american DIY tech geeks? 
Just curious,,sort of like, *WE know better*. 
Does jadis make design errors,, or do Jadis designers know their stuff,,,after all is said and done,,and RE done back to the way it was,,,?

These last words remind me,, ,,and the way it,,,was,,,Barbara Straisand. 
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