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Old 27th January 2021, 12:41 PM   #6741
InspectorGadget is offline InspectorGadget
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Yes, with all that Junk on the line; no chance of sorting the wheat from the chaff. thats really enormous. its like 25-35db higher than it should be. I think there are far too many variables in application to make someone elses measurements applicable to you.
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Old 27th January 2021, 12:59 PM   #6742
bohrok2610 is offline bohrok2610  Finland
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LM317 regulators with Cadj cap are in the low hundreds of nV/√Hz so the overall noise level is quite high. Also the mains related hash is too prominent. Maybe you should first try to clean that.
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Old 27th January 2021, 01:14 PM   #6743
kozard is offline kozard
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Quote:
Originally Posted by InspectorGadget View Post
Yes, with all that Junk on the line; no chance of sorting the wheat from the chaff. thats really enormous. its like 25-35db higher than it should be. I think there are far too many variables in application to make someone elses measurements applicable to you.

Trying to figure that out right now.


And this is with the DAC output measuring about 30 dB improvement already. (2nd and 3rd harmonic at the limit of the ADC of my SB0490.)
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Old 27th January 2021, 01:22 PM   #6744
kozard is offline kozard
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I have attached voltage waveforms from AVCC_R (powered by the stock AMS1117-3.3) and the input of the AMS1117-3.3.

The AMS1117-3.3 input is the output of the stock LM7805 which itself is being powered by an external 9.6V regulated HPRO/Harman Pro regulated power supply for musical instrument effects processors.

A square wave would explain all the higher harmonics...


Any ideas what is going on? Anyone have measurements to share? I would like to see what it looks like when it is working well. I am going to work on the power supply just in case the HPRO supply is outputting something ugly.


[Edited: The channel one scale is obscured in the screen capture. Not a good feature!]
Attached images in order:
  1. [100uV/Div] AVCC_R Idle
  2. [500uV/Div] AVCC_R 1kHz Full Scale
  3. [500uV/Div] AVCC_R 1kHz Full Scale Zoom In
  4. [500uV/Div] Regulated Input To AMS1117-3.3 Idle
  5. [500uV/Div] Regulated Input To AMS1117-3.3 1kHz Full Scale
  6. [500uV/Div] Regulated Input To AMS1117-3.3 1kHz Full Scale Zoom In
Attached Images
File Type: png AVCC_R Voltage_Idle.png (109.2 KB, 60 views)
File Type: png AVCC_R Voltage_1kHz_Full_Scale.png (105.5 KB, 59 views)
File Type: png AVCC_R Voltage_1kHz_Full_Scale 2.png (97.9 KB, 62 views)
File Type: png Input to AMS1117 Idle.png (78.8 KB, 63 views)
File Type: png Input to AMS1117 1kHz Full Scale.png (112.5 KB, 61 views)
File Type: png Input to AMS1117 1kHz Full Scale 2.png (106.7 KB, 12 views)

Last edited by kozard; 27th January 2021 at 01:27 PM.
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Old 27th January 2021, 01:27 PM   #6745
bohrok2610 is offline bohrok2610  Finland
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Could you try with battery instead of HPRO?
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Old 27th January 2021, 01:30 PM   #6746
kozard is offline kozard
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Quote:
Originally Posted by InspectorGadget View Post
Yes, with all that Junk on the line; no chance of sorting the wheat from the chaff. thats really enormous. its like 25-35db higher than it should be. I think there are far too many variables in application to make someone elses measurements applicable to you.
Not saying it would be applicable to my board. However I would love to see measurements on a very good or great ES9038Q2M example. Certain noise and spurs will come from the ES9038Q2M and it would be helpful if I knew what was "normal" in a very good or great ES9038Q2M example.

Last edited by kozard; 27th January 2021 at 01:37 PM.
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Old 27th January 2021, 01:31 PM   #6747
kozard is offline kozard
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Quote:
Originally Posted by bohrok2610 View Post
Could you try with battery instead of HPRO?
I am presently looking at a stack of 18650 cells and 18650 holders with that exact thought in mind.

Last edited by kozard; 27th January 2021 at 01:35 PM.
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Old 27th January 2021, 01:35 PM   #6748
Markw4 is offline Markw4  United States
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People have measured power rails with an AP before. The machines can do it if there are things there that show up well on an audio FFT. RF switching spikes that might or might not cause problems might only be visible on a good scope.

There are some things an AP simply does not measure very well, but that do affect sound. There are linear distortions, and various different types of noise. Some noise and or so-called linear distortions may be time variant. Some small linear distortions may change rather slowly over time and or temperature, and some of those changes may be audible.

There are clock jitter effects, which can be quite complex in sigma-delta dacs like ES9038Q2M. One model when jitter is small enough is that the width of an FFT skirt is the convolution of clock phase noise with the audio test signal (widest down at the root, where the close-in phase noise is largest). It means clock close-in phase noise can dynamically mask small signals close in frequency to larger signal, so you can't hear the smaller signal. More discussion at: ESS Sabre Reference DAC (8-channel) ...post #2651

Moving along, there is also the matter of left/right channel timing stability relative to each other, which is also affected by clock jitter. One way we localize the lateral position of sound in front of us is by the very small differences in the time it takes the sound wave to reach each ear. Numbers in the nanosecond range are given for interaural localization sensitivity. Some more info: Sound localization - Wikipedia



So, lots of stuff that can be audible which an AP doesn't show very well. That said, if an AP shows a problem then by all means its good to try to fix the problem. Just don't mess up the other stuff that is audible in the process. Also, IMHO and IME its best not to ignore problems you can hear even if it doesn't show up on an AP.

Last edited by Markw4; 27th January 2021 at 01:46 PM.
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Old 27th January 2021, 01:59 PM   #6749
bohrok2610 is offline bohrok2610  Finland
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Quote:
Originally Posted by Markw4 View Post
People have measured power rails with an AP before. The machines can do it if there are things there that show up well on an audio FFT. RF switching spikes that might or might not cause problems might only be visible on a good scope.

There are some things an AP simply does not measure very well, but that do affect sound. There are linear distortions, and various different types of noise. Some noise and or so-called linear distortions may be time variant. Some small linear distortions may change rather slowly over time and or temperature, and some of those changes may be audible.

There are clock jitter effects, which can be quite complex in sigma-delta dacs like ES9038Q2M. One model when jitter is small enough is that the width of an FFT skirt is the convolution of clock phase noise with the test signal (widest down at the root, where the close-in phase noise is largest). It means clock close-in phase noise can dynamically mask small signals close in frequency to larger signal with noise, so you can't hear the smaller signal. More discussion at: ESS Sabre Reference DAC (8-channel) ...post #2651

Moving along, there is also the matter of left/right channel timing stability relative to each other, which is also affected by clock jitter. One way we localize the lateral position of sound in front of us is by the very small differences in the time it takes the sound wave to reach each ear. Numbers in the nanosecond range are given for interaural localization sensitivity. Some more info: Sound localization - Wikipedia



So, lots of stuff that can be audible which an AP doesn't show very well. That said, if an AP shows a problem then by all means its good to try to fix the problem. Just don't mess up the other stuff that is audible in the process. Also, IMHO and IME its best not to ignore problems you can hear even if it doesn't show up on an AP.
There is a fundamental flaw in your thinking. If the phenomen cannot be measured there is no way to make real, objective improvements. You can of course rely on your hearing when testing your tweaks but that does not necessarily mean that you are improving anything. It may well be the other way around. Our brains are different and so is our hearing, background, music taste etc. Unless you perform controlled listening tests you cannot say anything universal about your improvements. But it goes without saying that if it sounds good to you, that should be sufficient (to you).
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Old 27th January 2021, 02:14 PM   #6750
Markw4 is offline Markw4  United States
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bohrok2610,

You argue a philosophical opinion. I disagree with that opinion. I think humans can be used as test instruments and so does Sean Olive. JBL uses test panels of human listeners to evaluate speakers. They do it blind of course. The thing is that speakers are made for human enjoyment, not for measuring gravity waves. I would argue that dacs are for human enjoyment too. And I do have ways of doing very, very good listening tests, sometimes blind, but not always. Training and experience of a test panel can go a long ways towards obtaining objective results.

Last edited by Markw4; 27th January 2021 at 02:22 PM.
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