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Old 22nd August 2012, 08:26 PM   #11
EUVL is offline EUVL  Europe
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Gentlemen,

You have a once-in-a-lifetime chance to learn from professionals like Mr. Wurcer, Mr. Marsh, Mr. Curl, maybe even Mr. Jung, .....
on how to design opamps for audio without worrying about cost of production and what not.

Why would one want to miss it ?

Anyway, if it is not your cup of tea, I am sure there are other more entertaining threads on the forum.
Why not just let those interested have some fun ?


Cheers,
Patrick
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Old 22nd August 2012, 08:27 PM   #12
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Also, why limit to 8 transistors?
Seems arbitrary.
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Old 22nd August 2012, 08:32 PM   #13
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Why not ?
My JFET DIP8 discrete opamp use 7. And it is 3 stage.
So we can do better.

Pass Discrete Opamp in DIP-8 Package

No challenge, no fun.


Patrick
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Old 22nd August 2012, 09:24 PM   #14
jcx is offline jcx  United States
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Default challenge is determining technical specs for "good audiophile performance"

transistor count games aren't about meeting performance goals

even when counting stages you get waffling from Curl, Hansen about cascodes, cascaded followers
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Old 22nd August 2012, 09:32 PM   #15
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We need a prize. How about a free copy of Linear Audio? (or a 1 year subscription!)
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Old 22nd August 2012, 09:34 PM   #16
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I was not going to say anything, but why would you want to MAKE something that you could get from an electronics 'junkyard'? '-)
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Old 22nd August 2012, 10:35 PM   #17
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Quote:
Originally Posted by john curl View Post
I was not going to say anything, but why would you want to MAKE something that you could get from an electronics 'junkyard'? '-)
Possibly, a well designed discrete amplification unit will sound better than any existing opamp.
However, in such a case the challenge should aim at an amplification unit.
Even when talking about opamp per se, possibly a well designed discrete one will sound better than any currently existing commercial one.
In such a case, a superb sound quality should be listed along other requirements.
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Old 22nd August 2012, 10:36 PM   #18
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Well, I am not qualified to do this engineering design work, but Mr. Marsh seems to have an idea about what he is looking at/for, so perhaps he will take the lead and present a proposed topology...?

And, what about things like error correction circuitry and feed forward, etc...? Just rambling in public. Don't worry, maybe I am not talking to myself, I have a bluetooth and am on the phone in reality...

_-_-bear

PS. don't forget the commercial opamps from Burson?
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Old 22nd August 2012, 10:49 PM   #19
RNMarsh is offline RNMarsh  United States
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Quote:
Originally Posted by jcx View Post
transistor count games aren't about meeting performance goals even when counting stages you get waffling from Curl, Hansen about cascodes, cascaded followers
It must be competitive with what is out there already.
It is less of a challenge to do better with more.

[ I could allow cascoding to be considered as a single transistor if it cant be done otherwise. Current sources, diodes might not be counted]

BUT - Scott wanted to do a discrete version for audio of the 627 opamp and that is fine with me. I dont want to start doing something Scott did not say he wanted to do.

A discrete opamp circuit of 627 opamp would be nice for others to compare with the integrated version.


-RNM

Last edited by RNMarsh; 22nd August 2012 at 11:03 PM.
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Old 22nd August 2012, 11:01 PM   #20
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Quote:
Originally Posted by Joshua_G View Post
Possibly, a well designed discrete amplification unit will sound better than any existing opamp.
Absolutely correct. Without "Opamp topology" limitations it is easier to achieve better sound reproduction. When you listen you don't care about such things inside like CMRR or open loop gain on 1 Hz frequency. But if it has to be opamp by conditions, I would take one lowest noise double opamp chip, one powerful opamp, and using nested feedbacks construct from them an opamp with wide bandwidth and flat frequency response way beyond audio band, low noise, inourmously high CMRR, and great load driving capabilities. And it will still be discrete, using discrete chips and resistors. Try to beat it using transistors and resistors only.

Jan, where is my magazine copy? I won already.
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Last edited by Wavebourn; 22nd August 2012 at 11:04 PM.
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