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Old 26th April 2018, 05:05 PM   #851
system54 is offline system54  Germany
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Old 26th April 2018, 05:12 PM   #852
DJDestiny is offline DJDestiny  Singapore
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Quote:
Originally Posted by Markw4 View Post
Moving along, while I am waiting to hear back from an ESS distributor to inquire about non-disclosure and a datasheet, I decided to go ahead a try a couple of other things I have been thinking about. However, I did make multiple changes at once, so can't say for sure how much effect each one has. Sorry.

Attached below is yet another photo. After some thought, I decided it might make the most sense to treat the oscillator clock as HF analog, rather than digital. Therefore, it got its own 3.3v low noise regulator. Also added some 1,000uf caps where the power comes into the board. Some film caps were added previously while experimenting with and otherwise working on power supply noise issues.

It turned out that the silent switcher did not like the big 1,000uf capacitive loads and it started causing some odd noises in the DAC output even with the volume all the way down. So, the SS is gone and the DAC and headphone amp are both on the linear power supply.

It sounds very good, but not quite as much of the most subtle details as the reference system which includes a Benchmark DAC-3 and Benchmark ABH2 power amp. The reference system is extremely detailed, probably not wrong to say state-of-the-art detailed. It makes a pretty challenging comparison.

Having made the comparison, the Chinese DAC is still quite good. IMHO, it is definitely a keeper as it is now. It is dynamic, has good well-defined deep bass, detailed and realistic cymbal sounds (one of the hardest things to reproduce accurately in a DAC and amp, it seems), and so forth.

Next steps will be to see if I can get a datasheet here and start testing what can be done to get master mode I2S working.

In parallel with I2S, and as I have time, my notch filter is now working, I need to do some calibration and testing on that. Hopefully, before too long I will be able to post some basic DAC measurements.
For filtering switchers you might want to consider a LC filter with MLCC ceramic caps rather than a single huge cap, reasons being, electrolytic caps are very bad at high frequency and also as you found out most switchers don't like huge bulk capacitances either. (They already have bulk capacitance at their output if they're designed properly with a LC filter)
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Old 26th April 2018, 05:14 PM   #853
democles is offline democles  Netherlands
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Including this one on the PCB.

The 1,65v out of the 3,3v.

Yes you can always make your own spiderweb.
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Last edited by democles; 26th April 2018 at 05:16 PM.
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Old 26th April 2018, 05:40 PM   #854
Markw4 is offline Markw4  United States
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Quote:
Originally Posted by DJDestiny View Post
For filtering switchers you might want to consider a LC filter with MLCC ceramic caps rather than a single huge cap, reasons being, electrolytic caps are very bad at high frequency and also as you found out most switchers don't like huge bulk capacitances either. (They already have bulk capacitance at their output if they're designed properly with a LC filter)
Right, understood. The caps were put in to help with another issue, it was just a byproduct that the switcher was affected.

Also, agree that LC filters with appropriate HF caps should work better to filter out switcher noise that is conducted RFI/EMI. The radiated stuff is another issue. For low-cost off-the-shelf designs the EMI tends to go everywhere.

Anyway, the linear supply just didn't have those issues. Diode commutation noise was already taken care of. But I know well designed switchers can work very well. Some quasi-resonant designs produce little noise to begin with, for example.
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Old 26th April 2018, 05:49 PM   #855
Markw4 is offline Markw4  United States
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To cut to the quick with the sample files, it turns out the sample rate conversion process also changed the levels a little. The effect of that is that 16-44 version sounds better in some ways, punchier for example. Turning the volume down on it makes it sound weak and muddled in comparison. Frequency response is the same in all of them throughout the audible range. Loudness differences can easily make that sound different.

The thing to listen for to start with are the cymbals and cymbal tails as they fade out. How much like a real cymbal do they sound. Not like bursts of noise or gritty/grainy. So long as no resampling by the OS, the higher bitrate files should sound more smooth and real when listening to that. Once you start to latch onto the cymbal SQ then the HF on everything else starts to sound more real, when the brain starts processing that information. That being said, there is no chance the cymbals can get near to real sounding at all until most or all of the mods have been implemented. Once the distortion is down, it is possible to hear pretty much exactly how well the recording was made. On the album used to make the samples there is some distortion, just a little though. However, its easy to think you have removed all your distortion contribution to the sound and then find out not so when you lower it some more.

I should probably just go back and renormalize all the files. Its a bit more processing but it should help get rid of the loudness effects.

Last edited by Markw4; 26th April 2018 at 05:58 PM.
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Old 26th April 2018, 07:39 PM   #856
androa76 is offline androa76  Slovenia
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Hi Markw4. Thank you for you effort. You did great job.
But this download test is not the right way. Please do that way. Use one original 44.1khz, 24/96 or 192kz file that we can unload it. Than send it trought dac and Adc and we will compare original file vs dac out file. I am interested how was changed vs original.
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Old 26th April 2018, 08:36 PM   #857
Markw4 is offline Markw4  United States
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androa76, I have an idea I want to try first. It will take me awhile to get to it though. Everything takes time, and right now my time I have available for this is focused mainly on getting the DAC into master I2S mode. Progress continues, but there have been some issues to sort and I am working on another new one now.

I'll get back to this later though, when I can.
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Old 28th April 2018, 01:21 AM   #858
Markw4 is offline Markw4  United States
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Just a quick update. Got DAC into I2S master mode (128fs_mode) with all clock signals coming out. Sent those signals into the SRC chip operating in slave mode, and it is producing I2S data going back into the DAC.

Problem is the DAC is staying muted and not clear yet exactly why. I have tried some different settings, and sent off a question through the DAC chip distributor for clarification of some data sheet information (the data sheet is a bit on the minimal side, as data sheets go).

So, kind of waiting for a response and waiting to go at it again maybe tomorrow. Possibly sleeping on it for a night will help, sometimes it does actually.

In the meantime any questions are of course welcome. Happy to help if I can.
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Old 28th April 2018, 01:35 AM   #859
Markw4 is offline Markw4  United States
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Regarding upsampled test files, I am still thinking about that one too. People are very easily fooled or misled by volume level differences at little as .1dB. Sample rate conversion will cause come volume level change.

What I usually do is adjust the volume up and down for each file and try to ignore any perceived changes in frequency response, punch, sound stage, etc., that change with volume. Unfortunately, it takes some practice to learn how to hear the other things that don't perceptually change with volume level.

In addition, a reproduction system has to be good enough to not obscure those small differences. Many or most systems tend to be lacking in that respect, which is part of the reason I encourage adding a low-cost modified headphone amp to the project. But, the DAC will need to modded enough or otherwise good enough to reveal subtleties too.

What I could do with the sample rate test files to help keep people from getting distracted by perceptual effects of level differences could be to level match them to around .01dB.

However, I can't just normalize them digitally to the same level because the sample locations in the analog waveforms have changed due to resampling. Therefore they would have to be level matched after passing through reconstruction filters to find the true levels. I can do that, but it is a slower more laborious process. Maybe I will play around with it while waiting for a reply on the data sheet question.

Lest anyone think the subtleties I refer too above must be too small to bother with, once you listen to a good DAC for awhile and get used to more of the good sounding little details being there, you sure notice it when they are missing. Doesn't work the other way around though maybe because people don't suddenly learn to notice new things instantly unless the new things are big enough or particularly stick out in a way that tends to attract attention.

Besides long term exposure or long term listening, there are other ways to learn to hear the small details faster and better that are taught to recording and mastering engineers, but usually that is done when people are sitting in the same room and listening to the exact same source. I can tell you though that the training generally tends to start with listening very, very carefully to cymbal sounds. Why? I don't know, it just seems to work with humans. If you try different things with people its usually the cymbals they seem to be able to learn fastest with at first.

Last edited by Markw4; 28th April 2018 at 01:50 AM.
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Old 28th April 2018, 03:20 AM   #860
Mikett is offline Mikett  Canada
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Markw4
One question I have to ask is this. That suboptimal (bad) recordings exist is a fact. Can you comment on whether the better the DAC, the more this class of recording becomes more obvious? to the point of atrocious and wanting to stop the playback? How does the DAC3 handle bad recordings? Is it more listenable or less? I need to know that because is getting this board closer to the DAC3 going to make more of my library "bad"?
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