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Samuel Groner's super opamp
Samuel Groner's super opamp
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Old 13th May 2019, 02:36 PM   #1
jan.didden is offline jan.didden  Europe
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Default Samuel Groner's super opamp

In 2017 Samuel Groner, with Martin Polak, published a new composite opamp design: Journal of the Audio Engineering Society ENGINEERING REPORTS, Vol. 65, No. 5, May 2017: Low-Distortion, Low-Noise Composite Operational Amplifier.

Late last year I was looking for a very low distortion opamp and thought I'd give this a try. I laid out a small adapter PCB for a DIL08 foortprint, see pics. The result was all I expected, an opamp with distortion specs literally out of this world. I was not able to verify the claimed THD < 180dB (yes you read that correctly) but got numers at -160dB and better.
I'll post measurements in my next post.

Anybody here build this as well, experiences?

Jan
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File Type: jpg 20190506_093359.jpg (262.5 KB, 1560 views)
File Type: jpg 20190506_095319.jpg (262.9 KB, 1502 views)
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Last edited by jan.didden; 13th May 2019 at 02:58 PM.
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Old 13th May 2019, 02:39 PM   #2
jan.didden is offline jan.didden  Europe
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Here are some measurements with the AP SYS2722. The AP cannot directly measure that low, so I put the opamp in an inverting configuration with a 12 ohms resistor between the two inputs, giving a (measured) noise gain of 50.3dB.

So for all these measurements, you need to subtract another 50.3dB from the shown values. As I said, exceptional!

Jan
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Old 13th May 2019, 03:00 PM   #3
Mark Johnson is online now Mark Johnson  United States
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Samuel Groner's super opamp
Jan, thanks very much for this. It is extremely impressive.

If I remember correctly, Samuel Groner's website used to contain schematics for four or five different all-discrete opamps. One of them was a composite opamp made with all discretes having circa 180dB dc gain. But using Google and the Internet Wayback Machine, I can only find three of his discrete opamps today: "simple", "low noise", and "high voltage" (SOP, LOA, HOA abbrevs by Groner). Does anyone have a copy of the schematics and written descriptions of the others, especially the composite opamp? Would you please post them on diyAudio or, if not, please send me a PM.

Again congratulations and thank you.

Last edited by Mark Johnson; 13th May 2019 at 03:02 PM.
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Old 13th May 2019, 03:04 PM   #4
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Impressive!
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Old 13th May 2019, 03:13 PM   #5
jan.didden is offline jan.didden  Europe
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Quote:
Originally Posted by Mark Johnson View Post
Jan, thanks very much for this. It is extremely impressive.

If I remember correctly, Samuel Groner's website used to contain schematics for four or five different all-discrete opamps. One of them was a composite opamp made with all discretes having circa 180dB dc gain. But using Google and the Internet Wayback Machine, I can only find three of his discrete opamps today: "simple", "low noise", and "high voltage" (SOP, LOA, HOA abbrevs by Groner). Does anyone have a copy of the schematics and written descriptions of the others, especially the composite opamp? Would you please post them on diyAudio or, if not, please send me a PM.

Again congratulations and thank you.
Mark, I am not familiar with the others. If you have access to the AES library it's worthwhile to get this paper, but I shouldn't post it here, its (c)-ted.
Note that my measurements put the 2nd at about -165dB with 7.5V out on a 375 ohms load, making it even more fantastic.

Attached is Samuels' own measurement. Boring ;-)

Jan
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File Type: png groner-copa.PNG (16.4 KB, 1543 views)
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Last edited by jan.didden; 13th May 2019 at 03:18 PM.
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Old 13th May 2019, 03:30 PM   #6
syn08 is offline syn08  Canada
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Quote:
Originally Posted by jan.didden View Post
In 2017 Samuel Groner, with Martin Polak, published a new composite opamp design: Journal of the Audio Engineering Society ENGINEERING REPORTS, Vol. 65, No. 5, May 2017: Low-Distortion, Low-Noise Composite Operational Amplifier.

Late last year I was looking for a very low distortion opamp and thought I'd give this a try. I laid out a small adapter PCB for a DIL08 foortprint, see pics. The result was all I expected, an opamp with distortion specs literally out of this world. I was not able to verify the claimed THD < 180dB (yes you read that correctly) but got numers at -160dB and better.
I'll post measurements in my next post.

Anybody here build this as well, experiences?

Jan
Interesting.

Both OPA211 and THS4031 are well known for very low distortions, but it is obviously the huge loop gain that is responsible for -180dB distortions.

Since I don't have access to the JAES paper, could you post a few details about:

a) Is this composite op amp unity gain stable?
b) Any results about the open loop gain and phase?
c) Any details about the response in capacitive loads?
d) How was -180dB distortion measured? Is -180dB @ 10KHz as suggested by the graph?
e) Is the -180dB number in inverting or non inverting configuration? That is, are the common mode distortions included or not?
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Old 13th May 2019, 03:44 PM   #7
scott wurcer is online now scott wurcer  United States
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Quote:
Originally Posted by jan.didden View Post

Attached is Samuels' own measurement. Boring ;-)

Jan
Just think he was able to make all these measurements without audiophile blessed components.
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Old 13th May 2019, 03:45 PM   #8
EUVL is offline EUVL  Europe
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A true opamp has no Gnd connection.
So how did you solve that ?
To the negative rail ?


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Old 13th May 2019, 03:52 PM   #9
jan.didden is offline jan.didden  Europe
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Yes, those are the important questions, right. A text excerpt: "First and foremost, it should be appreciated that the novel composite operational amplifier is conditionally stable only. Sufficient phase margin is (except at very low frequencies) only available near the unity open-loop gain frequency. The composite operational amplifier must thus be operated with a unity loop gain frequency close to the unity open-loop gain frequency. In many cases this implies the use of an additional feedback capacitor instead of a purely resistive feedback network." I had no stability issues with 22p across Rf. There is also a diode clamp on output of the 1st opamp to avoid it slamming into the rails at switch-on and other transients.

Jan
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Cable: a potential source of trouble interconnecting two other potential sources of trouble - Erik Margan
Linear Audio pubs and articles . The SilentSwitcher now at diyaudio store SilentSwitcher. Keeping in touch with SY.

Last edited by jan.didden; 13th May 2019 at 03:55 PM.
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Old 13th May 2019, 04:03 PM   #10
EUVL is offline EUVL  Europe
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Reminds me of Jim William's Super Gain Block.

Analog Circuit Design Volume 2: Immersion in the Black Art of Analog Design
Fig. 36.95



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