2. amps-preamps
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Line Stage Preamplifiers AX vs AU

Just learning a  few things about these components,,, seems to me best tube fora  linestage (PREamp term should only be applied to a  amp with phono section/ w/o phone, = Line Stage) anyway,, seems to me best circuitty for a  *passive line stage* would be the 12AU7 tube,  and not employ any 12AX7's. 
The AX ha s a mu of 100, so it really scrams and thus pushes the db level too much as it reaches the pwoer amp.
The AU has a  mu of only 15, so its alsmost passive, which is really whata  line stage should be , just passing the  signal from the source to the amp,  with the least involvement, IMHO alot of line stage amps, have too much coloration and muddiness due to the usage od 12AX7's. 
Leaving me with voting the only  line stage  employing all 12AU7 circuitry i know of under $2K as best Line stage on the market. 


https://en.cayin.cn/products_info?itemid=120
mozartfan
mozartfan OP
2,143 posts
 
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.

mozartfan OP
2,143 posts
 
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. 

atmasphere's avatar
atmasphere
12,128 posts
 
@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.
yogiboy's avatar
yogiboy
5,875 posts
 
@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.
atmasphere's avatar
atmasphere
12,128 posts
 
@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.
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