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Old 26th September 2021, 11:18 PM   #1301
syn08 is offline syn08  Canada
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Default Off topic, dedicated to Gerhard

Here's what the PN9000 I got for almost nothing can do; Attached is a 26GHz signal phase noise from a hobby fun level synthesizer I built some time ago. TI LMX2594 chip based plus a Hittite HMC577 doubler, from the time chips were chips in the DigiKey shopping cart, not abstractions in a manufacturer catalogue.

The phase noise sucks, of course, this is only to show what some TLC can do to an instrument.

P.S. Among other minor issues, the 100MHz OCXO was working here and there, more like "there". Since I had nothing better to do with it, I cracked open the Wenzel 2x1 inch metal brick inside, and got the disappointment of my life. A PCB with a discrete PLL driven by an 100MHz, allegedly SC cut, crystal, in a TO5 case. The board had cold solder joints and some corroded PCB traces, from the foam used to isolate the board. Which was certainly acidic, since the insides had a distinct vinegar smell after opening. It's an old VCXO of the 500- series (meaning built to custom specs, no data sheet available for the public) but even so, I was not expecting such blunders from nobody else but Wenzel. Melted the hot glue used to attach the board to the metal shell, pulled the board out, repaired the corroded traces, walked a soldering iron across the solder joints, closed the brick, it is back to life, but to God knows what performances... It will be replaced with a Morion OCXO, anyway, pretty soon.
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Last edited by syn08; 26th September 2021 at 11:34 PM. Reason: P.S. added
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Old 26th September 2021, 11:30 PM   #1302
5th element is offline 5th element  United Kingdom
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Well I mean -126dB took almost zero effort to achieve. I am absolutely sure you could get quite a bit better than this if you took the time to do so. The power is there, via the THD compensation, you just need to work it long enough to get the desired result.

I don't think getting 0.00002% or whatever is unreasonable. The difficult thing, as you mentioned, is showing that it's stable, repeatable, and consistent across drive level and frequency. It's pointless if it's only useful at one static set of variables.
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Old 27th September 2021, 12:59 AM   #1303
Terry Demol is offline Terry Demol  Australia
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Quote:
Originally Posted by 1audio View Post
You could infer assuming the noise is constant across the band. I think it would buy 20 dB in a 100 KHz band if my mental arithmetic is working.
In terms of DR, once you account for BW and A-weighting specs AD4630-24
looks roughly equiv to the stereo ESS Pro ADC.

TCD
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Old 27th September 2021, 02:08 AM   #1304
IVX is offline IVX  Ukraine
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Quote:
Originally Posted by 5th element View Post
The ES9822 THD compensation isn't just limited to the 2nd and 3rd harmonics. You calculate the entire polynomial and coefficients to be programmed into the correction registers.

I am assuming that you could, theoretically, add in as many orders to the equation as you want but the resolution for storing the final result might be limited.

With enough patience, trial and error, and a clean enough signal source, you could compensate down to 0.00002% in my opinion. Whether or not this is necessary, or reliable, is another matter.

I've got a dual mono 9822 acting as slaves. For optimum compensation I'd want to split these into stereo ADCs first and then compensate the left and right channels separately. Then do this for both ADCs. 4 separate sets of finely tuned THD compensation coefficients and out to the 5th harmonic if I really want to push it. I cannot be bothered to do this though.

For simplicities sake I tried using one set of THD compensation coefficients for all 4 channels and only targeted the 3rd harmonic. With the 2nd/4th down at -140dB+ they don't need any attention it's just the 3rd and 5th that really do.

Regardless, the simple compensation gives me 0.00005% THD and 0.00008% THD+N with ARTAs A weighting at 0.5dBfs which is as good as I can realistically expect from the AK4499 signal source as I've measured when using a notch.

The THD compensation holds across frequency and sample rates too.
I've found the platinum sample, kind of king from 26pcs ADCs, with SNR 129.2db(A) and THD+N very close to -125db.
Cosmos ADC DR 129db(A) platinum sample - YouTube
Instead of A-w, you can insert a fake mic response file to limit BW of THD+N in Arta to get +/-.3db matching vs AP digital analyzer. BW20_20k.mic - Google Drive
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Last edited by IVX; 27th September 2021 at 02:33 AM.
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Old 27th September 2021, 05:41 AM   #1305
phofman is online now phofman  Czech Republic
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Quote:
Originally Posted by 5th element View Post
With enough patience, trial and error, and a clean enough signal source, you could compensate down to 0.00002% in my opinion.
Since the exact algorithm of the linear interpolation is detailed in one of the ESS ANs, IMO there is no need for trial and error. Just measure the distortion vectors, calculate the optimally-compensating polynomial curve of the required order, and enter its values for the interpolation boundaries to the chip.


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The THD compensation holds across frequency
Does it indeed in your measurements and to what extent? IME static polynomial compensation fails at lower and higher frequencies ADCs and DACs for audio instrumentation applications .
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Old 27th September 2021, 09:41 AM   #1306
syn08 is offline syn08  Canada
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Interesting, is there a place to download ESS ANs for people having a signed NDA? Or I could ask for, if I would know what…
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Old 27th September 2021, 01:00 PM   #1307
5th element is offline 5th element  United Kingdom
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Quote:
Originally Posted by phofman View Post
Does it indeed in your measurements and to what extent? IME static polynomial compensation fails at lower and higher frequencies ADCs and DACs for audio instrumentation applications .
I didn't save the measurements I took of distortion vs frequency as I only made them quickly. This was to assess whether or not the compensation was working for other frequencies besides the 1kHz I was using to adjust the compensation.

There were no obvious issues at the frequency extremes except for the gentle rise you'd expect to see at high frequencies and then the gentle rise at low frequencies for the AK4499 based on the RC filter created by the vref cap.
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Old 28th September 2021, 01:00 PM   #1308
IVX is offline IVX  Ukraine
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5th element, what about SNR you got with 9822?
BTW, I brought the ADC_Int_Sel parameters for all 4 ADCs to the Windows app because you can really find a better SNR if you change the recommended 0xB e.i. 11 to something else even different values in the pair ADC1 = 11, ADC3 = 15 as an example. Some chips up to .3-.5db better vs recommended 11.
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Old 5th October 2021, 12:19 AM   #1309
5th element is offline 5th element  United Kingdom
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It depends what program I use. ARTA gives -127.5dB(A) and audioTester -128.7dB(A). These are both with the ADC without any input stage attached though, which obviously causes things to deteriorate.

I actually get better noise figures with an AK5578 in stereo mode, at least with 44/48kHz material. But the ESS DAC gives much better distortion.
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Old 5th October 2021, 07:18 AM   #1310
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Quote:
Originally Posted by 5th element View Post
It depends what program I use. ARTA gives -127.5dB(A) and audioTester -128.7dB(A). These are both with the ADC without any input stage attached though, which obviously causes things to deteriorate.

I actually get better noise figures with an AK5578 in stereo mode, at least with 44/48kHz material. But the ESS DAC gives much better distortion.
>> AK5578 in stereo mode

You should get better noise figures with mono mode... interesting that AKM ADC is in noise figures any better.

Or any chance to parallel the ESS ADC to mono mode?

So this means no "Hyperstreaming" used as on DAC.

>> But the ESS DAC gives much better distortion

Is this a tipo, while expected the ESS ADC ...?
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