Line Stage Preamplifiers AX vs AU

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.

Cheers George

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

The Cayin SC6 Mark2, IMHO will shootout ~~any~~ preamp under say $4K,,and beat out some priced at $15K+. 

~~$12K~~ for those curious on the price of the ET7S2. 
Hope I'm not stepping on any USA fans toes here,,,but come on,  the Chinese  engineers /lab has the USA lab  beat by a  grand slam,,  In the shootout~~ would  have Cayin smoking  CJ's britches down before he even thought about drawing the gun....
soundstage, resolution, purirty, fidelity, dynamics, colors (Non coloration), musicality. 
One lab  would rate high,,the other lab  dismally low. 

Ck out the inners of the ET7
https://www.google.com/search?sxsrf=ALeKk000cEXXWHIR2WLzEcPIdr2LEC72Ww:1597803619764&source=univ&tbm=isch&q=conrad+johnson+et7s2+images&sa=X&ved=2ahUKEwj2kLSpmqbrAhVGI6wKHYlDAUsQsAR6BAgMEAE&biw=1280&bih=625#imgrc=IX4YdWXUnrLDbM&imgdii=bU510li4ZoQnoM

Sorry I don't want my digital fq's passing through THAT mess.

Now for a super high craftmanship design point/point wiring, ~~Scaffold crafted~~~ with pure silver wire.
Dual super high quality trans. etc etc
Now THATS a circuitry worthy of my digital source to pass.


https://en.cayin.cn/products_info?itemid=120

also note in CJ’s web page,, **and as with all our products , we give special attention to service of our units**,
Cayin is built on the very same level as Jadis,, = they never fault. You do not need ever worry about service, as you will not need a servicing tech. The track record of cayin is 20+ years, zero repairs.
Same as Jadis, 20+ yrs, no need for service.

NOTE ck the weight
CJ @15 lbs
Cayin SC6Mark2 @ 25 lbs
=No brainer. 

@mozartfan  You might want to hear what a 6SN7 does for a line stage. The 12AU7 is based on the 6SN7. Actually the 6CG7 is a 6SN7 in a miniature envelope, and the 12AU7 is the same geometry as the 6CG7 but with half the plate area.

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

12BH7 vacuum tube is a medium mu dual triode. 12BH7 was designed as a driver in TV sets. 12BH7 Tube is capable of driving plenty of current with low distortion. This makes it ideal as a driver for power tubes in modern tube audio amplifiers. 12BH7A tube with suffix ’A’ has a controlled heater warm-up for use in a series filament circuit.

@yogiboy  Yes, but you have to deal with the filament wiring, as the 12BH7 has a 12V center-tapped filament similar to a 12AU7. The 6CG7 can only be operated with 6.3V filament voltage. But the rest of the pin basing of the two tubes is the same, and BTW the 12BH7 is the same '9A' basing as the 12AU7, so if the circuit can operate with the increased filament current, the 12BH7 can operate the same socket. Due to minor differences between the 12AU7/12BH7 though, to really find out what they sound like the cathode circuit will need a slightly different value depending on which tube is in the socket.

@atmasphere
Thanks for the Info! My amps use 12BH7 tubes so I am going to try some 12AU7 tubes that I have sittin’ around!

You might want to hear what a 6SN7 does for a line stage

I’ve seen this pretube in a few of cayin/Line magentic integrated designs,,, nice looking tube for sure,,, 20 mu factor = niceeee.
Thing is I love the Tele AU,,and the Jadis Dpl has now 3 AU’s, as per Richard Gray mods.
He swaped out the AX for AU,, making some changes by eliminating a pair of .47 m evo oil caps,,, we just listened at his shop,, but he has Heathkit monos, and a pair of radio Shak vintage speakers, refurbished,,so hard to make a valid assessment vs my Defy7 modded with M caps + Seas Thor MTM..
Richard is anxious to see how i hear the AX swap to AU.
But yeah, the 6sn7 looks like a fine pretube.

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. 

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. 
...

ok  woke up this morning,, and you were on my mind and YOU were,,,couldn't resist humming that tune just now,,,anyway,, I figured out why the american DIY/tech geeks are wrong about jadis' Line stage design , so called << The Issues with that french design>> OK, the tech elimintaeda  the 1st tube, which was a a  12AX7,,, now with that gone, he figured,,**oh now you can turn the gain up on the vol and have more resolution, more db level ** etc,,not sure what his ideas are/were,,anyway, Jadis ' Line Stage are famous for their gain. On any Jadis Line stage from my 20 yr old DPL to their falgship $50K line stage JA500, it only takes <<less than>> 1/4= 1/3 on the vol knob to have bountous SLAMM/db levels. 
I mean mean your amp will ,,,,rock on,,,oh my soul...anyway,, with the 12AX7 out, now 3 12AU7's in,  the sound is mushy/flat,,, oh yeah you can turn vol up more,,but all that jadis voicing is ,,gone.
The lone 12AX7, has a  mu of 100, this circuit needs that 12AX&, to push the fq 's through the 2 12AU7's,, and in spite of all the popular opinions that the cd buffer 12AU7 stage  is not needed, and a  complete waste,, that the AUX for cd sounds <<so much better>> to my expierience in my system the cd buffer sounds superior , not by much, but in our rule of thumb,, << a  nuance is a nuance>>
The cd buffer is in fact superior to the AUX,, Owners of the DPL have the old stock caps,, once they change the caps to Mundorf Silvergold EVO oil,, then they will hear the nuance come through... anyway,  back to Linestage designs.. So what Cayin did with their Mark2, LS6 Line stage is employ 4 12AU7's.. with a  pair of retifer tubes,,now you think,, well according to your theory, a  pair of 12AU7's per channel, is noy going to offer enough mu to push the fq's, / going to sound mushy/flat,, well what cayin did, is add a  <<true pure  dual mono trans circuit>> NOW with a  pair of trans, the fq's has that boost to drive the fq's through the circuit.,\
I've seen on YT a  tech guy showing his work of having swaped out the caps in a CJ 10 line stage/preamp,, and had to turn vol control up <<significantly>> = leads to distortion,, The more you crank the vol control up, more mushy fq's/distortion you will pass through the circuit.

IMHO The cayin LS6 mark2, is the finest preamp under $2K.

No I have not heard PL's new line of Linestage amps,, which stat at $2K,, I did have their older Prologue model and   found the sound stage to be <,weird>. Like spagettiED.
Cayin and PL made at Spark's labs,,  designs are close, but NOT the same / one will sound different from the other lab.
As I say, I've not heard the new PL Linestage amps,, but my hunch is , if you are on a  budget, the $1500 Cayin is the best Linesage  made today. 
Cayin will blow away Conrad Johnson's linestage/preamps. 
Of course CJ's is 3X's ,, mabe 4X 's the price of the LS6 mark2. 
I'd bet the Cayin LS6 gives Jadis' $$$$$$$$$ Linestagea  run for their money. 
With the cayin, at 1500, vs the Jadis LS,, you've got tons of leftover cash to take out the Cayin caps  and employ Mundorf  high value caps and also switch out Cayin'sTakman  carbon Film resistors to  Takman Metal Films.. and see which you prefer,,, I myself much prefer the metal,, the carbon are too <<smooth>>  = lacks dynamics.