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Old 11th December 2012, 08:35 PM   #8071
as_audio is offline as_audio
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Quote:
Originally Posted by Joachim Gerhard View Post
Your circuit idea drawn up comes soon. It is immensely workable. Hats off.
.. and wallet open please ..
No, nobody will pay me for that cause I am not a highly paid Electrical Engineer .

Indeed it's an old hat as we say, remember our examination in "Impulstechnik" in
Paderborn (Prof. Nowack from Bochum) some 30 years ago. Evaluation of a circuit
like that in your post 8063

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without the npn was part of the questions. Nothing new under the sun.

Last edited by as_audio; 11th December 2012 at 08:40 PM.
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Old 11th December 2012, 08:40 PM   #8072
Joachim Gerhard is offline Joachim Gerhard  Germany
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Look at the little drawing. That buffer is decent and can be improved on.
Sure, if we go under the audible threshold with distortion, noise and bandwidth one PN junction less may sound better. I always look at it as a very bad capacitor.
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Old 11th December 2012, 08:43 PM   #8073
Joachim Gerhard is offline Joachim Gerhard  Germany
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Do not wory, a friend of mine is working to bring out the MPP thread as a book.
The title is " Book of Thread".
That will make us rich, no question (:
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Old 11th December 2012, 08:48 PM   #8074
Joachim Gerhard is offline Joachim Gerhard  Germany
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That study in Paderborn was "Hard Bread" as we say here. Somehow in the back of my mind it must have being ringing a bell.
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Old 11th December 2012, 08:54 PM   #8075
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Originally Posted by Joachim Gerhard View Post
That study in Paderborn was "Hard Bread" as we say here. Somehow in the back of my mind it must have being ringing a bell.
I am pretty sure I only remember this exam question, because I did not see the cascode at the time and was consequently downgraded. And so my long folded cascode journey started.
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Old 11th December 2012, 08:55 PM   #8076
Joachim Gerhard is offline Joachim Gerhard  Germany
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Of cause the PNP BJT in the folded cascode has the same purpose of reducing the input capacitance of the J-Fet array BUT with the additional series cascode we can run the J-Fets
on lower voltage, that reduces gate current plus heating and that reduces noise. We also can run that cascode on quite high voltage ( provided we are under the avalanche voltage of the BJT that is another source of noise ) so we have more dynamic range.
I am undecided on this .
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Old 11th December 2012, 08:58 PM   #8077
Joachim Gerhard is offline Joachim Gerhard  Germany
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I did not realize that this is a cascode back then. Folding the cascode was VERY exotic in the 70th. Maybe only John Curl new it since the 60th (:
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Old 11th December 2012, 09:01 PM   #8078
Stefanoo is offline Stefanoo  Italy
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ok I have spectacular news for everybody.
I modeled the circuit, we can get the required gain (hopefully same applied in practice).
Also same exact capacitors and value for the RIAA I gave away in these pages can be used to have same exact precision had on Paradise.
Noise wise we are on the good side.
so now the circuit looks very, very promising which means that all the people who took part to the GB will be able to use the same capacitors to build this one too.

EDIT: Output is still out of phase with the input, which is still not a big deal anyway, but I jsut wanted to correct my previous statement.
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Last edited by Stefanoo; 11th December 2012 at 09:25 PM.
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Old 11th December 2012, 09:38 PM   #8079
Stefanoo is offline Stefanoo  Italy
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and here is the circuit for the joy of everybody.
Unfortunately I won't be able to do much work in the next days as I want want to work on the new linestage design I am helping out with a very regarded user if this forum.
I like to work on both but unfortunately it is impossible...so here is my contribute for now.

Here we go fully simulated and apparantely working (The resistors still need tweaking to get absolute precision)
Attached Files
File Type: pdf BasicIdea Rev2.pdf (35.8 KB, 92 views)
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Old 11th December 2012, 10:37 PM   #8080
Joachim Gerhard is offline Joachim Gerhard  Germany
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Plus - minus 45 V.
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