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Old 23rd October 2018, 02:24 PM   #3031
terry22 is offline terry22
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Quote:
Originally Posted by Markw4 View Post
Hi terry22,
Haven't heard from you for awhile. Don't know if I scared you off with LT1763 modding or not? If so, no reason to give up. I'm sure something can be worked out for beginners that will be satisfactory.
Hi Mark,
Sorry for being silent.
I was pretty busy at work for the last 3 weeks...
I received at the end of last week the ak4137, the xmos and my new 1.07 board.

AK4137 is working ok except for some dsd files. (btw which filter do you use?)

Does the xmos need a psu or is it feed by the usb cable?
(Till now, I always used I2s)

I got my new clock I will try to solder it on a old 1.04 board I have in order to train myself and not ruining the new board.

I'm still waiting for the prototype boards.
Do you have a mouser reference for the copper foil?
It looks that there is hundred of them and I don't know which one to buy.

Hope the mods went well.
I have several pages of the thread to read to catch up.

Last edited by terry22; 23rd October 2018 at 02:45 PM.
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Old 23rd October 2018, 02:49 PM   #3032
Markw4 is offline Markw4  United States
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Hi Terry,
XMOS is powered by USB.

Thing about soldering your new clock to your old 1.04 board, if it works that means you are going to be upgrading the 1.04 board for all the mods then, if that is what you intend. You certainly don't want to solder the new clock to the old board, then unsolder it, the re-solder it to the new board.

You could remove and replace the original clock on the 1.04 board for practice if you want. Maybe the most important thing when unsoldering an old clock to take it gently and try not to scratch up the solder mask on the dac board while doing it since that helps the solder only stick where you want when it comes time to solder a clock back on as the next step. By the way, I did write some more recently about clock replacement soldering.

I don't have a Mouser reference for copper foil. I bought some using ebay and some from amazon.

Regarding AK4137 and playing DSD files, I haven't tried it and that could be a limitation of using it. It certainly seems to help with PCM files. Maybe there is some way to bypass AK4137 when playing native DSD files, haven't looked into it but maybe will have to.

Last edited by Markw4; 23rd October 2018 at 02:56 PM.
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Old 23rd October 2018, 04:19 PM   #3033
terry22 is offline terry22
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Quote:
Originally Posted by Markw4 View Post
Hi Terry,
XMOS is powered by USB.

Thing about soldering your new clock to your old 1.04 board, if it works that means you are going to be upgrading the 1.04 board for all the mods then, if that is what you intend. You certainly don't want to solder the new clock to the old board, then unsolder it, the re-solder it to the new board.

.
thank you! good to know
I was about to solder it on the old board for testing it.
I read your post about the clock. Very interesting.
When I unsoldered the clock on my old board it was pretty clean.
I will try to do the same on the new.

Problem with dsd files is fixed.
The problem was the rpi and SoX.
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Old 24th October 2018, 12:02 AM   #3034
Terry Demol is offline Terry Demol  Australia
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Quote:
Originally Posted by Markw4 View Post
As an update on harmonic distortion compensation adjusting software, I received some more information on Arta. I am planning to give it another try to see if I can get it to do what I want. If successful, I will describe the process here in the thread.
Mark,

I'm using Arta with EMU1212M. I wasn't aware of the bit depth restrictions of
the freeware version. I'll have to check that. It surprises me because I was
able to do decent loop through verification of 1212M performance and it
appeared to meet the spec.

This was a while ago, I'll see if I can get time to check this out again.

T
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Old 24th October 2018, 12:18 AM   #3035
Markw4 is offline Markw4  United States
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Hi Terry,
In the sound card setup the unlicensed version has a grayed out setting for wav bit depth, which is locked at 16-bits. I don't know if it only applies to in relation to reading and writing wav files. If only files, then the signal generator and spectrum display depth may be 24-bit.
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Old 24th October 2018, 12:26 AM   #3036
Terry Demol is offline Terry Demol  Australia
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Quote:
Originally Posted by Markw4 View Post
Hi Terry,
In the sound card setup the unlicensed version has a grayed out setting for wav bit depth, which is locked at 16-bits. I don't know if it only applies to in relation to reading and writing wav files. If only files, then the signal generator and spectrum display depth may be 24-bit.
OK, I don't remember that, will check it out.

In the meantime, have a look at this one:

AUDio MEasurement System download | SourceForge.net

cheers

T
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Old 25th October 2018, 12:30 AM   #3037
Markw4 is offline Markw4  United States
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An update on the new modded dac: Got the harmonic distortion compensation to work with Arta running in demo mode (freeware mode).

Found this 2nd version of the dac didn't need any C2 adjustment at all, but it has some low level odd harmonics that do affect the sound and that did benefit from some adjustment of C3.

C3 was minimized at a setting of -157, however that left C3 perhaps a little bit too much lower than C5, and it didn't sound subjectively best there. So, after some more listening tests we decided we liked -150 best for C3. (By the way, the default settings of HD compensation in the various dac registers is zero compensation, and HD comp 'disabled.' First thing is therefore to enable it before trying any adjustment settings.)

The C3 compensation difference between the default of 0 and a final setting of -150 used for this dac is pretty noticeable to us as we listen on the system here. I can only say it is definitely worthwhile to make use of the HD compensation capability if at all possible, as I think Allo found during their testing of Katana, and of course as Benchmark does for DAC-3. Same finding here. The effects are audible, and there will be a setting that sounds best.

By way of comparison, the first dac I modded came out with C2 = 5 and C3 = -7, IIRC. Quite a big difference from this second dac. The adjustment was audible as it affected complex music signals, even in that case.

My current plans include building an SMD version of the new schematic output stage and using it to upgrade the 1st modded dac. The AVCC circuit is already up to date, except no film caps. It uses a 10uf SMD X7R ceramic for LTC6655 filtering and organic polymers for opamp output filtering. We will see how it sounds with the new output stage, and if it seems like it might benefit from the addition of film caps for AVCC. Don't know when I will get started on that though.

Regarding Arta, I am operating the dac in PCM mode for making HD compensation adjustments. DSD noise floor is a bit too high to see the harmonics well even with signal averaging, but DSD for music playback still sounds best.

For the HD comp adjustments, used a 1kHz notch filter I made and which is handy to have around for various projects. I can describe how to build one and post some pics sometime. After the filter I go into an add-on low distortion preamp because my best ADC is calibrated for +24dBU FS, IIRC. It needs a lot of signal which means most people should not need an additional preamp like I am using. Without a notch filter, it is likely a sound card ADC will add a lot of its own HD from the high level 1kHz tone. With that frequency attenuated enough, there is no significant additional distortion contribution from the ADC data acquisition chain, so only dac distortion is seen in the FFT spectrum.

Don't know why more harmonic distortion in this dac as compared to the last one. Could perhaps have something to do with better gain matching and tighter tolerance resistors used in the 1st dac output stage. Had some .01% 10k resistors in stock that got used for the differential summing stage, and maybe the SMD I/V resistors just happened to be more well matched by luck. Haven't measured them to check.

Last edited by Markw4; 25th October 2018 at 12:33 AM.
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Old 25th October 2018, 02:41 AM   #3038
Terry Demol is offline Terry Demol  Australia
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Quote:
Originally Posted by Markw4 View Post
An update on the new modded dac: Got the harmonic distortion compensation to work with Arta running in demo mode (freeware mode).

Found this 2nd version of the dac didn't need any C2 adjustment at all, but it has some low level odd harmonics that do affect the sound and that did benefit from some adjustment of C3.

C3 was minimized at a setting of -157, however that left C3 perhaps a little bit too much lower than C5, and it didn't sound subjectively best there. So, after some more listening tests we decided we liked -150 best for C3. (By the way, the default settings of HD compensation in the various dac registers is zero compensation, and HD comp 'disabled.' First thing is therefore to enable it before trying any adjustment settings.)

The C3 compensation difference between the default of 0 and a final setting of -150 used for this dac is pretty noticeable to us as we listen on the system here. I can only say it is definitely worthwhile to make use of the HD compensation capability if at all possible, as I think Allo found during their testing of Katana, and of course as Benchmark does for DAC-3. Same finding here. The effects are audible, and there will be a setting that sounds best.

By way of comparison, the first dac I modded came out with C2 = 5 and C3 = -7, IIRC. Quite a big difference from this second dac. The adjustment was audible as it affected complex music signals, even in that case.

My current plans include building an SMD version of the new schematic output stage and using it to upgrade the 1st modded dac. The AVCC circuit is already up to date, except no film caps. It uses a 10uf SMD X7R ceramic for LTC6655 filtering and organic polymers for opamp output filtering. We will see how it sounds with the new output stage, and if it seems like it might benefit from the addition of film caps for AVCC. Don't know when I will get started on that though.

Regarding Arta, I am operating the dac in PCM mode for making HD compensation adjustments. DSD noise floor is a bit too high to see the harmonics well even with signal averaging, but DSD for music playback still sounds best.

For the HD comp adjustments, used a 1kHz notch filter I made and which is handy to have around for various projects. I can describe how to build one and post some pics sometime. After the filter I go into an add-on low distortion preamp because my best ADC is calibrated for +24dBU FS, IIRC. It needs a lot of signal which means most people should not need an additional preamp like I am using. Without a notch filter, it is likely a sound card ADC will add a lot of its own HD from the high level 1kHz tone. With that frequency attenuated enough, there is no significant additional distortion contribution from the ADC data acquisition chain, so only dac distortion is seen in the FFT spectrum.

Don't know why more harmonic distortion in this dac as compared to the last one. Could perhaps have something to do with better gain matching and tighter tolerance resistors used in the 1st dac output stage. Had some .01% 10k resistors in stock that got used for the differential summing stage, and maybe the SMD I/V resistors just happened to be more well matched by luck. Haven't measured them to check.
Interesting findings Mark, nice work.

You should post your results on the Blowtorch thread (HaHa) .

They are very low levels however, we did tests years ago introducing low
levels of H2 / H3 in an amplifier and found the same thing. We also had
similar results WRT H3 needing to be there, some amount of H3 is not a bad
thing.

Did you have any way of cancelling any harmonics above H5 or testing
audibility of them?

So I take it you acquired a data sheet and signed the NDA?

Do you have any FFT's with distortion cancellation?

One thing I have been wondering with Sabre DAC is if you can run pure
voltage OP and use the cancellation to linearize it. This opens up more OP
stage possibilities.


T
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Old 25th October 2018, 03:40 AM   #3039
Markw4 is offline Markw4  United States
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Quote:
Originally Posted by Terry Demol View Post
Did you have any way of cancelling any harmonics above H5 or testing
audibility of them?
Only H2 and H3 can be tweaked. So, nothing affected above that. However, I am curious why no H2, but a succession of odds. Will plan on looking at it a little more to see if I can affect it at all.

Quote:
So I take it you acquired a data sheet and signed the NDA?
Yes.

Quote:
Do you have any FFT's with distortion cancellation?
I forgot to grab a screen shot, but will try to get one next time I'm in there. Besides the odd harmonics, other imperfections I see are some 120Hz and a few harmonics above that which look to be line frequency noise. Don't know if they are from the dac or from the measurement system. In addition, the averaged noise floor looks higher below 1kHz. Don't know why, if it is an artifact of averaging, something from the notch filter, maybe from the 1/f noise corner of one or more of the LDO regulators for low voltage rails, or whatever else. So, there are some things that could be investigated and potentially improved, especially to the extent they may be real. However, it is the odd HD that I am currently most interested in, even though it is pretty low. It's still not as low as the 1st dac, and I would like to know to know why.
All the above having been said, it still sounds very good, no reason not to get to work on one. If I happen to find anything that can make it sound slightly better I will post here, but I wouldn't count on anything more turning up.

Quote:
One thing I have been wondering with Sabre DAC is if you can run pure voltage OP and use the cancellation to linearize it. This opens up more OP stage possibilities.
Yes. Occip did that and posted a big-ish number he found was optimal for H3 compensation. However, no one has compared the sound of doing that with the sound of doing a full blown current mode output stage with filtering, etc. According to ESS, current mode will give the least distortion. Don't know if they tried what occip did, but don't know why they wouldn't.

Last edited by Markw4; 25th October 2018 at 03:59 AM.
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Old 25th October 2018, 07:43 AM   #3040
Markw4 is offline Markw4  United States
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@Terry, Occip posted re his 2nd board coming in the same as the 1st for HD compensation for H3. None used for H2, IIRC. This is with the original voltage output stage, but with an AVCC mod: ES9038Q2M Board
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