Is the 9038 ESS hump the same thing that the THD compensation feature in the ESS DAC was to compensate for?
I can send you a link to download a bunch of test Tone files I generated in Adobe Audition if that helpsI'm going to try Audacity first, but if that doesn't do the job, I'll try WaveGene. Thanks!
Now for some hacking. Keep your fingers crossed.
Thanks, but I did create the test signals in Audacity. Much appreciated though.I can send you a link to download a bunch of test Tone files I generated in Adobe Audition if that helps
I don't know that John wanted to teach people how to fix the problem. He may have even misunderstood which issue we are talking about as we thought it was an IMD only issue at the time. Clearly though, John is very good at micro analyzing audio performance and likely enjoys very good support from ESS so has found and fixed this issue. Or avoided it somehow.
I think our effort here to keep analyzing it is good in figure out what is going on. We can get help then from our friendly manufacturers and possibly another push to ESS to listen.
If the problem is caused by DEM algorithm, there is nothing we can do about it.
To what extent is the hump a result of increased noise, harmonic distortion, and/or IMD?
Since the behavior of THD increase is only at specific level, I think the behavior of DEM(Dynamic Element Matching) is cause of the problem.
DEM is a noise shaper that removes the distortion made by multi-bit quantizer inside the delta-sigma modulator. It actually pushes the distortion to ultrasonic frequency so that the dac manufacurers can remove them using analog notch filter.
ESS is the first manufacturer as far as I know to use DEM to remove distortion and noise floor modulation.
This is the patent of ESS about their DEM architecture.
https://patents.google.com/patent/US7116257
For non-engineer, I recommend this link.
https://books.google.ca/books?id=8lwnzVwBbYcC&pg=PA44&dq=cmoset+high+end+audio+dac&hl=en&sa=X&ei=qAwHUc2NKunQigK1xYCoBA#v=onepage&q=cmoset high end audio dac&f=false
The problem is that the DEM which ESS is using is too old. TI, Cirrus Logic, Asahi Kasei also have their own architecture and they develop new algorithms every time they launch a new series of dac. But It seems that ESS didn't make such thing since their first Hyperstream architecture. I am not sure if they really did or not because ESS don't share enough information. But this can be the cause of thd increase at certain range of output level.
For example, this is part of the paper that one of the engineer of Asahi Kasei published at 2000.
View attachment 19126
this is the explanation of 'dip' of SNDR in conventional DWA(Data Weighted Algorithm, most typical method of DEM)
"The sharp dips in the traces are typical artifacts of DWA. Because of the periodic nature of DWA, the shaped mismatch error appears as tones. These out-of-band tones may fold back to inband due to limit cycles that are dependent on the signal level, and degrade the in-band SNDR."
If the problem is caused by DEM algorithm, there is nothing we can do about it.
Has anyone had a chance to check out the effect of this thread on the big ugly part of the audio world where tubes, vinyl and subjective emotions reign supreme? It's, obviously, very easy to lose sight of the fact that, despite the mysterious distortion hump in the current iteration, ESS DAC devices pretty much rule the roost right now because of their (otherwise) superlative performance. There are those on audio forums who proudly declare that they find any ESS-based converter “painful” [substitute pejorative of choice].
Are these folks now celebrating that, with Amir's ‘discovery’ of the ESS hump, the reason for the “painful” sound of ESS is now apparent to those objectivist fools?