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Old 9th August 2020, 01:47 PM   #5841
Mikett is offline Mikett  Canada
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Moving from 9038Q2M to a 9028Pro board

A little off but worthwhile since I started with the ESS9038Q2M.
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Old 11th August 2020, 03:11 PM   #5842
Green77 is offline Green77  Sweden
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Quote:
Originally Posted by Markw4 View Post
Hi Daniel,
Yes, +-12v should work okay.
Thanks, i ask the question again 😊
Is it even possible to use +/-9v?

BR // Daniel
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Old 11th August 2020, 03:43 PM   #5843
Markw4 is offline Markw4  United States
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You could probably get away with +-9v. The opamp or opamps need to be operated within their datasheet voltage limits, and the if using the dac onboard regulators to drop the + opamp rail down to +3.3v for the digital circuitry, then those regulators need to be operated within their datasheet dropout voltage specifications (they are likely to regulate better if not operated at the very lowest input voltage possible, it can help to have a few volts across them). Some similar dac boards dropped the +15v power down to +5v or +8v (see what it says on the first regulator), then from there down to 3.3v. If they are LDOs then the dropout voltages will be lower than if they are conventional regulators.

Regarding +- voltage rails for opamps, the voltage can affect sound quality. Usually higher tends to be better, but for AK4499 dacs using OPA1612 I/V opamps it turned out that +-11v sounded cleanest. Only why to find out is to try some different opamp rail voltage settings, then listen and or measure distortion for each voltage level.

As far as a recommendation goes, I probably wouldn't want to go below +-11v even though it would probably still work at, say, +-9v. Also, please use a good linear power supply for that, not SMPS or wall warts of any kind to start out with because its more involved to clean up the power coming from them. Better not to have dirty power in the first place, if possible.

For transformers, R-core are best for minimizing ground conducted noise from the AC line.

Last edited by Markw4; 11th August 2020 at 03:47 PM.
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Old 12th August 2020, 06:23 AM   #5844
Green77 is offline Green77  Sweden
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Thanks Mark,
Reason for asking was that i had a power board with low noise at +/- 9v.
I guess i can try it and compare with my 12 v 78xx board.

BR// Daniel
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Old 12th August 2020, 12:55 PM   #5845
Markw4 is offline Markw4  United States
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Daniel,
That sounds like a plan. Please let us know what you find, if anything.

Also, if it were me I would want to improve the sound of that board. One of the steps in that process involves separating the opamp power from the digital power. Your +-12v supply would probably be great for the opamp circuitry. On the other hand, a low noise +9v supply might be good for feeding the local 3.3v regulators that provide stable power for the clock, DVCC, and VCCA. That leaves AVCC, which is a tough one to get get right. We usually prefer to power it with opamp buffers and a low noise +3.3v reference. Its one of the first and most important things to talk about in more detail if you decide you want to improve dac sound quality.
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Old 12th August 2020, 07:16 PM   #5846
Green77 is offline Green77  Sweden
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Thanks,
Yes i was thinking about try to seperate the powerlines.
Is it that easy to cut the trace from the 7808 and feed something like 9v there?
I also have some two leftover 3,3v low noise regulator.
Maybe i can use them? But not sure where. I will use optical in so maybe some improvment there?
Also, in post #353 there was something about current mode?
Is it that easy that doing like in that post?

Many questions, sorry.

Edit: my Swedish spelling...

BR // Daniel
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Old 12th August 2020, 09:03 PM   #5847
Markw4 is offline Markw4  United States
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Quote:
Originally Posted by Green77 View Post
Thanks,
Yes i was thinking about try to seperate the powerlines.
Is it that easy to cut the trace from the 7808 and feed something like 9v there?
Yes, something like that. Best to keep wires from the power supplies to the dac board pretty short.

Quote:
I also have some two leftover 3,3v low noise regulator.
Maybe i can use them?
I used three 3.3v low noise regulators mounted on the back side of the dac board (ground plane side). One regulator for DVCC, one for VCCA, and one for the clock. The MCU can stay on the original 3.3v regulator that's already on the board.

Quote:
I will use optical in so maybe some improvment there?
Optical tends to be pretty jittery. Best to try to use good quality optical cable and keep it short, if possible.

Quote:
Also, in post #353 there was something about current mode?
Is it that easy that doing like in that post?
The dac board comes with a one opamp voltage mode output stage design. It is *much* higher distortion than a proper 3-opamp current mode output stage design. The output stage and the AVCC power supply are two of the very biggest sound quality improvements that can be made. However, its some diy work to make it happen. Schematics for recommended output stage and AVCC supply are attached to post #3003.

A through hole output stage project with construction pictures is available at: Dropbox - Output Stage Instructions.zip - Simplify your life
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Old 13th August 2020, 02:24 AM   #5848
syn08 is offline syn08  Canada
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Quote:
Originally Posted by Markw4 View Post
Optical tends to be pretty jittery. Best to try to use good quality optical cable and keep it short, if possible.
Data to support this statement?

Detailed measurements of SPDIF and TOSLINK cables showed absolutely no difference between them, also cable length and quality has virtually no impact.

Archimago's Musings: MUSINGS: "Audiophile" Digital Cables... [Updated November 2013]
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Old 13th August 2020, 11:48 AM   #5849
Markw4 is offline Markw4  United States
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There you had one person saying his opinion based on his measurements. I didn't see any phase noise plots for different cables, so I remain unconvinced of his claims. And, yes I am on the side that believes phase noise at low offset frequencies matters a lot. I can hear it and so can other people who bother to listen. Others differ, as we all know.
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Old 13th August 2020, 03:27 PM   #5850
syn08 is offline syn08  Canada
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Understood, you have no data, your opinion is based on subjective hearing experiences only.

FWIW, facts based on measurements are not "opinions" by any metric.
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