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Old 9th October 2012, 07:38 PM   #211
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I think we made a J-Fet version of post 200 too. I just can not find it at the moment.
One advantage of the totally balanced is 6dB more gain so this is less of an issue.
I like the basic simplicity of the one shot and the high gm J-Fets come handy here.
For totally balanced is has to be modified.
The 2SJ74 is the only P-channel low noise part on this planet at the moment.
Even for me it is getting harder and harder to obtain them.
A single high gm differential stage solves that problem.
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Old 9th October 2012, 07:47 PM   #212
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interesting! Do you think there is a reason why they wouldn't make high gm low noise P-CH Fet? This just seems so strange! No one needs it?

When I build R6 of master piece I thought that the 6dB gain would have been enough to reach the 62dB-ish mark, but I was wrong.
With the Jfets I could just get to 56-ish balance usint 16 Jfets at Idss.

I agree with you, the one-shot looks simpler and has the potential of using only the high gm Jfet.


Consideration on the IF3602: granted it has very low noise and high gain, does it say how linear it is? That I guess is a big pro for the Toshiba's over other Jfets.
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Old 9th October 2012, 07:53 PM   #213
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Linear Systems promised a P-channel since several years. As far as they know they handed out samples on a Rocky Mountain show so they can make it. I did a major effort to get more information but did not succeed.
Why they do not bring that to market i have no idea. Also lateral mosfets are getting rare and both issues give me a lot of trouble because some of my commercial offerings need this parts.
I think Scott Wurzer knows more about the Interfets and as far as i can tell they work fine.
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Old 9th October 2012, 08:04 PM   #214
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Quote:
Originally Posted by Joachim Gerhard View Post
Linear Systems promised a P-channel since several years. As far as they know they handed out samples on a Rocky Mountain show so they can make it. I did a major effort to get more information but did not succeed.
Why they do not bring that to market i have no idea. Also lateral mosfets are getting rare and both issues give me a lot of trouble because some of my commercial offerings need this parts.
I think Scott Wurzer knows more about the Interfets and as far as i can tell they work fine.
If you talk to Linear System they say they will release the J74 anytime now...which is obviously not true.
Reason why they wouldn't is unknown, but I confide they will.
Said that , the Toshiba's fet only have small gm.

My question is: why do manufacturer make a ton of different BJTs semiconductors and Vertical mosfets but they don't produce new Jfets dual, complementary and so on?
What is the main reason? It must be commercial, but I don't see why the electronic's world wouldn't need a complementary pair of very linear Jfets.
Honestly, BJTs in my opinion have little to offer compared to Jfets other than a big variety and higher gain.
If the Jfets could be made to these extent Jfet would be much more succesful.

What do you think?
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Old 9th October 2012, 08:29 PM   #215
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I see AD797 opamps in 10.000,-$ phono stages so most people accept 1nV/qHz noise.
Also double differential and parallel symmetric discrete stages are quite rare.
The only bigger company i know is Accuphase.
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Old 9th October 2012, 08:32 PM   #216
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Here is the Accuphase C27. The circuit is a bit traditional but it homes in on very good measurements.
http://www.accuphase.com/cat/c-27_e.pdf
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Old 9th October 2012, 08:34 PM   #217
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They use bipolars for phono MC.
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Old 9th October 2012, 09:03 PM   #218
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Quote:
Originally Posted by Joachim Gerhard View Post
I see AD797 opamps in 10.000,-$ phono stages so most people accept 1nV/qHz noise.
Also double differential and parallel symmetric discrete stages are quite rare.
The only bigger company i know is Accuphase.
I am not so disconcerned for the 1nV/Hz noise that is not the quitest in the planet however could be enough for vinyl reproduction, but mostly for the use of AD797 for the follwoing reasons:

1) they charge that high price and parts inside are just standard op-amp which design wise don't require that much of an effort if compared to an all discrete stage.

2) Sound of an opamp on the signal parth is not the best compared to the very best discrete stage and while I could expect that for entry levels I don't accept it when I pay that much.



Now, I know you make OP-AMP based high-end phono premaplifier and I am sure they are great sounding so there is no intention to attack your precious work, and I am an ignorant if compared to your experience, so I would really be very interested to know your take on this.
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Old 9th October 2012, 09:13 PM   #219
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Quote:
Originally Posted by Joachim Gerhard View Post
Here is the Accuphase C27. The circuit is a bit traditional but it homes in on very good measurements.
http://www.accuphase.com/cat/c-27_e.pdf
looks like a very nice discrete phono stage!!! A two stage desing and I am surprised they would choose BJTs on the FE with the cart.
Maybe the input offset is not so much a concern as I think it is.

However, isn't it too complex in your opinion?
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Old 9th October 2012, 09:14 PM   #220
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Is it wrong to assume that an Opamp sounds worse than discrete? If it does sound worse, what would be the reasons for this. I know a few that were designed by very talented individuals in the business, who also love music. Really just wandering and seeking opinions from more experienced listeners and designers.
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