Line Stage Preamplifiers AX vs AU

Yep, thats what i got from Richard Gray's explanation as he was modding my Jadis DPL, 
haven't heard it yet, but i'm confident i will  much prefer the 12AU7 in the 12AX7 socket.
You can raed through this thread and see most folks prefer the AU over the AX. 
The AX is too forward,, especially if you havea  powerful push pull amp.

The lone AX in the DPL is  passing too much gain to the Defy7, allowing hardly any room for the Defy to come alive. 

It will be 2 weeks before i get my system up N running, so can't say for sure, but hunch is  a all AU circuit ina  line stage is superior to a  AX+ AU linestage,
AR, CJ, PL, all have AX+ AU.  Jadis also employs a  AX + AU circuitry. 
The AX  100mu amplification  voices too strongly IMHO. 
Best to have dual 6922 digital source passing as quietly through the linestage source as possible,  = more passive, which is the ideal goal ofa  line stgae circuit.
Allowing more head room from the  power amp to work. 
https://www.diyaudio.com/forums/tubes-valves/287283-12ax7-vs-12at7-vs-12au7.html

From what I remember, for line stages AU, AY, are better, AX usually for high gain MM or MC phono stages. AT's for drivers.

No AY's please, 
But OK so i can see a  AX for phono section,, which is why i titled this topic, ~~Line stage~~ only.
AU's are slightly  superior to AT's, as far as sonics, fq, sound stage = magic of a  pre tube. 
I just sold a  all 12AT 3 stage(3 pairs of AT'S!!) line stage amp today,. Not as  forward  voicing as the Jadis's DPL  single 12AX7.
That is to say, the DPL's lone AX voiced as higher/higher db level vs the 6 AT7's. 
The cayin is the only linestage under $2K that i know of which uses a  100% 12AU7 circuitry. 
PL which is made at the same lab, has AU/AX Circuitry. ,,No I take that back,, some PL line stage, the newer bigger models  do offer all AU circuitry. 
I listened to a  older PL model with AU/AX, and did not care for the soundstage. 
Leaving me more convinced a  all 100% AU line stage is the best circuitry for a  line stage.
 

ck out the gains on this new CJ phono pre section,,wow, a  wopping 54/40 db levels,,, = packing a  punch for LP listening,, ..
the aux for cd player is at 27 db. still way too high.. at least for my preference/needs/wants/desires..... 
The Cayin is 15db,  for cd resolution, the Cayin beats out the CJ. 
That is unless you love screaming db levels for digital source..,, then yeah go with the CJ. 
My room is 10x12, 8 foot ceiling = 27db just from the linestage,, , hardly turn the gain on the vol up anymore than a  few clicks of the vol knob = too forward = not enjoyable,, would be like listening to a  CJ as main component, and the Defy just sitting there using less than a  few watts of power. = I want to hear the Defy as 1st voice, , then the digital source 2nd voice, , then the linestage circuitry as passive as possible.
https://conradjohnson.com/classic-2-vacuum-tube-preamplifier/

 it really scrams
READ ,, so at 100mu really SCREAMS the fq's. passing through...

CJ's newest line stage says **triod**, you would THINK, = A X or AU or AT,,no employs a  single 6922, which might bea  triod, i don't know,,, buta  single 6922 ina  line stage??? how is that tube , the glory of true tube circuitry?
and then read the review,
where the guy says,
The real purpose ofa  line stage is to pass the music, with the very least amount of influence/coloration** 
Yes, correct,,, But he also fails to complete the sentence,, **with the highest fidelity to the sonic fq;'s comming from the digital source,,** ahhh, thats the critical value of a  ~true high fidelity line stage~~~ , passing fq with purity, naturalness, ~~FIDELITY~~( That ancient term Philips coined wayyy back at the very beginnings,, but which has gotten toss aside , lost among high powered selling  ads, promos and such)

Price? 
ha, get out your AMEX Gold card.
https://conradjohnson.com/wp-content/uploads/2020/04/HiFi-182-conrad-johnson_HR.pdf