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ESS THD ‘Hump’ Investigation

bennetng

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View attachment 23535
I find this graph from another review puts things in a context for people that own these ESS-based devices. It shows that even at the highest point of the hump, the performance is still comparable to the Modi 3 using USB.

Amir, would you say that the D50 has a better IMD performance than the Modi 3 via USB because for the majority of the range, the distortion is actually significantly lower? Or does its lack of predictable linear behaviour actually make it equal or worse compared to the Modi 3 using the USB?

It would also be great to know whether there is any statistical information concerning the percentage of audible content that is found between -40 dBFS and -20 dBFS for music. I could see a lot of classical pieces have a significant portion of content here, but pop music would likely be found between -0 and -20 dBFS.
Modi3's USB measurement is greatly improved after a driver fix.
https://www.audiosciencereview.com/...ts-of-smsl-sanskrit-10th-dac.5702/post-127305

 
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BYRTT

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Would be interesting to see the measurements of the Accuphase DC-950 DAC based on the 9038Pro chip.....
If its because you interested in pro series then as far as we informed over at diyA site in the row of units behind Amir there's a 8 channel 9028Pro waiting to stare into AP analyzer, and by the way when we at it creator of that new unit had a post about "Sabre hump" over at Khadas TB thread here is the link (https://www.audiosciencereview.com/...hadas-tone-board-dac.4823/page-19#post-122993)

LINK to post at diyA site (https://www.diyaudio.com/forums/ven...8-launch-tour-announcement-2.html#post5727188)

Link to product (https://www.oktoresearch.com)
 

amirm

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Amir , I dont think the hump exists because of the PCB layout . Might be because of ASRC (that most design use)...except Katana. Are you able to see the hump (or test for it) ?
It is very hard to test because I can't easily control it with the AP. I did take a shot at manually testing it though when I reviewed the Katana: https://www.audiosciencereview.com/...and-applepi-raspberry-pi-dacs.4164/post-97196



So it appears to not be an issue in Katana.

I can see PCB impacting noise but not as much distortion. Is it a loading issue?
 

Music1969

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Amir , I dont think the hump exists because of the PCB layout . Might be because of ASRC (that most design use)...except Katana. Are you able to see the hump (or test for it) ?
Pro-Ject Pre Box S2 DAC doesn't use ASRC. I believe @amirm will be re-testing one (a user will be sending one in).

It also allows the user to enable 'distortion compensation'.
 
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johan

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From our understanding its an issue with dpll.asrc enabling on ess9038/28 all flavors.

I will give more details in about 1 month when our new DAC will be fully tested .
 

Veri

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From our understanding its an issue with dpll.asrc enabling on ess9038/28 all flavors.

I will give more details in about 1 month when our new DAC will be fully tested .
Awesome. ;)

new DAC? Will it be Pi-based?
 

Veri

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ASRC/DPLL is not the cause of this hump.
ESS official ES9038q2m demo board also uses ASRC, but it does not have this hump.
On the other hand, Gustard X26 disables ASRC in favor of their GPLL-M1. And it has no hump!
But, it could also be the output that is proper engineered with the Gustard...
 

johan

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Hmm , I never tested the EVM for the hump . However I doubt that all designs have improper output stage and I have the EVM schematic and it looks very close to commercial implementations.
 
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johan, do you think thd comp can solve this problem?
This hump has nothing to do with the I2C register setting and is a pure hardware issue.
If the layout of the I/V and LPF circuits is no problem, then only one or two key variables need to be adjusted to solve the problem.
But for work reasons, I can't disclose more details.
 
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Hmm - but the datasheet states:
"THD Compensation can be used to minimize distortion from external PCB components and layout
through the generation of inverse second and third harmonic components matching the target system distortion profile."
Maybe we are going in circles or are not talking about the same thing,
but as far as I was able to follow this thread, member "jackenhack" did not enable THD compensation yet?
 
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This hump has nothing to do with the I2C register setting and is a pure hardware issue.
If the layout of the I/V and LPF circuits is no problem, then only one or two key variables need to be adjusted to solve the problem.
But for work reasons, I can't disclose more details.
Mysterious :) Without disclosing anything confidential can you tell us whether there’s any chance of this getting fixed via a firmware update or is it only possible via a hardware revision?

Secondly, do you have an opinion concerning the audibility of the hump? I’m just wondering if this whole debate is purely academic if the hump is well below the threshold of audibility.
 

pos

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On the other hand, Gustard X26 disables ASRC in favor of their GPLL-M1. And it has no hump!
But, it could also be the output that is proper engineered with the Gustard...
Same goes for benchmark AFAIK: they use their own 200kHz asrc
 
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