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Old 14th August 2020, 10:43 PM   #5861
John Luckins is offline John Luckins  Europe
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Details of how Ben, the designer of the Soncoz SGD1 with dual ES9038Q2M's resolved the ESS Hump in linearity vs amplitude.

How to Fix ESS Hump on SGD1 and LA-QXD1 | Audio Science Review (ASR) Forum

John
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Old 15th August 2020, 07:34 PM   #5862
Mikett is offline Mikett  Canada
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Quote:
Originally Posted by John Luckins View Post
Sure, I'm using a PSU modified Soncoz SGD1. Same designer as for the Khadas toneboard. The designer solved the issue of the ESS linearity hump by correcting the opamp feedback capacitance/loading issue. It uses 2 X ESS 90382QM and fully balanced OPA1612 and RT 6863 Opamps for IV, supplied from separate regulators and transformer. Sounds and measures excellent out of the $470 box. Easy to do supply mods and versatile inputs. Saw off my heavily supply modded Katana with ease.

John
John can you show us the innards of the SGD1 and what mods have been done.
Always interesting to see what is possible.
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Old 18th August 2020, 10:40 AM   #5863
Green77 is offline Green77  Sweden
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Hi all,

I did try low noise +/-9v to op but no improvment to sound, put my 12 v back.
In post #3003 it uses a ltc6655. Is it a 5v in 3.3v out regulator? can that be change to something else? Can’t find it at local store.

BR// Daniel
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Old 18th August 2020, 12:23 PM   #5864
Markw4 is online now Markw4  United States
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Hi Daniel,
The question of an alternate low noise 3.3v reference seems to be coming up more recently. In the past we have suggested use of something like LT3042 or LT3045 as a reference rather than as a regulator. They could be used either way and are easy to set to the correct voltage with one resistor.

A pretty complete off the shelf device could be: New LT3042 Ultra Low Noise Linear Regulator Power Supply for Amanero XMOS DAC G1 012|Replacement Parts & Accessories| - AliExpress ...although you have to talk to the seller to make sure they send you a 3.3v output version. Otherwise you might have to change a resistor yourself.

A cheaper option but that needs some setup configuration for your use might be: LT3042 PSRR RF Linear Regulator Power Module 20V 200mA Ultra low Noise Ultra high Board Reverse Battery Current Protection|Demo Board Accessories| - AliExpress ...I think we could help you figure out how to hook it up.

Although its not my favorite, TL431 seems to be everywhere. With extra filtering it might be made to work, but I haven't tried it in this application and am reluctant to recommend it.

Another thought people have suggested is GLED431 which is very low noise, but does not directly produce the voltage we want. Also, a complete 3.3v version such as we might use should be tested with a scope to make sure it doesn't oscillate. Makes it perhaps not ideal for beginners. https://refsnregs.waltjung.org/GLED4...014_092418.pdf

The thing about AVCC is that it has a big effect on the sound of the dac. IME, sound quality suffers if its not really good.

Last edited by Markw4; 18th August 2020 at 12:28 PM.
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Old 18th August 2020, 02:42 PM   #5865
Green77 is offline Green77  Sweden
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Thanks,

As you say Mark, TL431 is avalible.
If i remember correctly it can be calculated online if you know how much mA is used?
BR// Daniel
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Old 18th August 2020, 03:50 PM   #5866
Markw4 is online now Markw4  United States
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The TL431 datasheet explains how to apply it in Section 10, starting at page 22: https://www.ti.com/lit/ds/symlink/tl...oogle.com%252F
Best to study the whole datasheet, though. Not just one section.

Something to keep in mind that gave one user a problem: Strange oscillations with TL431 voltage reference - Electrical Engineering Stack Exchange

Possibly interesting TL431 blog: Reverse-engineering the TL431: the most common chip you've never heard of
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Old 18th August 2020, 05:02 PM   #5867
syn08 is offline syn08  Canada
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Quote:
Originally Posted by Markw4 View Post
That's sheer design incompetence. Set aside the range of output capacitors is clearly specified in the data sheet, every qualified designer knows that low ESR (film or ceramic) capacitors at a voltage regulator output will make the regulator sing, unless specifically designed to support such (which is always clearly specified in the data sheet).
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Old 18th August 2020, 05:27 PM   #5868
Markw4 is online now Markw4  United States
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Some of the people who want to use alternate circuits are not EEs. Just a heads up for those that don't even own a scope (of which there are quite a few). I don't see any reason to resort to name-calling or other derisive language, you were a beginner at some point too.

Last edited by Markw4; 18th August 2020 at 05:30 PM.
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Old 18th August 2020, 05:37 PM   #5869
syn08 is offline syn08  Canada
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Quote:
Originally Posted by Markw4 View Post
Some of the people who want to use alternate circuits are not EEs. Just a heads up for those that don't even own a scope (of which there are quite a few). I don't see any reason to resort to name-calling or other derisive language, you were a beginner at some point too.
Not all EEs are designers and not all designers are EEs. About those that don't even have a scope, they should probably look for another hobby.

If you spotted any name calling and derisive language above, please quote. When I was a beginner I was looking forward to learning from proven qualified people. And I purchased a scope to start with, that was lesson zero.
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Old 18th August 2020, 06:10 PM   #5870
Markw4 is online now Markw4  United States
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I would agree that finding a way to get an adequate scope is very important. IMHO, just as important as having an adequate DVM. That and learning how to use both. I say that for the beginners reading the thread who might want a 2nd, 3rd, or whatever opinion on the subject.
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