Discrete Opamp Open Design

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Here is a discrete op Amp. Seven SMT packages that are readily available.
not SOA but works via solder simulation.
 

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see JC thread -- goal: 627 performance in discrete design.

IMO cant require IC for dc servo in low gain apps and no large bulky coupling caps required to use this 627 goal equivalent.

OK, to get that here, from your post:

1) 8 transistors or less
2) drives 30 ohms with -105dB harmonics from 20Hz->20kHz
3) S/N -110dB (input shorted, 1Vrms output, unweighted)
4) no DC servo
5) DC offset on output less than 2mV under normal time/temp range
6) all of above with gain = 10 or less

Seems impossible to me but hey go for it. I got nothing.
 
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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
 
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.
 
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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Joined 2012
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
 
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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. :D
 
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