Best spec ADC Chip currently.... ??

[mansr]

How high it remains flat depends on how noisy your input (buffer) is.

 

[IVX]

perhaps, if your buffer on tl084

 

[Lightrock]

Indeed! A slight increase by about 10 dB up to Nyquist, as it seems - however, much gentler than the noise shaping slope of PCM4222 or AK55xx, for instance. I have only tested the ES9842Q with 96 kHz SR so far where the noise floor really looks perfect. Remarkable the absence of any spurs in your AP555 screen shots!

 

[Lightrock]

I don´t think the buffer amp is the culprit because its noise is getting shorted by the C across the analog IN_P/M pins.

 

[IVX]

AP555??

 

[Lightrock]

Sorry, your SYS2522. I thought it was the 555 because of the way too small characters at the x,y axis, but now I realize that the SW suffers the same disease on older models.

 

[chris719]

perhaps, if your buffer on tl084

Have you tried ADA4945-1? I have a non-audio design I have been meaning to test it in, but the specs look pretty good for the quiescent current, even in full power mode.

 

[IVX]

chris719, no. As I said, my front-end isn't balanced for simplicity, otherwise, I'll need 30 MOSFETs per channel. However, a fully differential version has to have noticeable better THD and crosstalk, and probably I'll make some Cosmos Pro later. Actually, the crosstalk of 9822 itself is around its noise floor level i.e. less than -160db, but the front-end crosstalk on a 2 layers PCB just -130db@1kHz and 1.8Vrms range(higher is worse). Such level of crosstalk affects the 2ch THD measurement because of harmonics level also at -130db or less. Currently, I try to improve the crosstalk and moved Cosmos to 4 layers PCB + some additional tricks but still within SE front-end. The XLR input, of course, has a differential opamp stage and inputs are balanced but from that stage up to the ADC the signal is SE.

 

[IVX]

 

[Tks]

Okay I gotta ask Amir what the ADC performance on his AP555x loopback is...

I didn't know it was technically possible to get that level out of ADC (DAC okay, but ADC?)

Then again, what the heck do I know..

 

[IVX]

Tks, APx555 uses AK5574 as I remember i.e. lower grade ADC, however, they use the ADC in collaboration with an analog notch filter and variable frequency. APx555 has a bit lower than -120db(some voltage range -117db, some -122db) THD+N resolution. Very cheap analog notch filter at fixed 1kHz frequency lets me to see THD+N -126db(0.00005%, actually, I didn't see less than 0.00006% so far but this is my sine-source issue) from 1 to 10Vrms.
PS: see attached APx555B residual THD+N(red one curve, blue curve SYS2***)

 

[IVX]

Looks like ESS also had the THD+N test of 9822 limited by their sine-source, I just filtered AP's analog generator and got -120db. I'm sure, without my far not ideal front-end the THD+N of 9822 can reach -121db or so.
Anyway, thanks ESS, Audio Precision analyzers will be cheaper soon. Can you imagine if $100 ADC board 90x50mm performance level between SYS2722 and APx555B($30750 basic option)?

 

[Tks]

Would have imagined JohnYang to topple AP eventually in some form. Seems you're gunning for their performance in the ADC realm.

You should look to making an interface like the Motu M2/M4 or something...

 

[capslock]

IVX, absolutely cool! Is this just for your own testing or will you sell this as a board or even dongle? SPDIF or I2S out would already good for us diy or recording enthusiats, USB interface would be the icing on the cake!

 

[capslock]

Or even better, ADC and DAC in one dongle, a mini AP beater the size of a matchbox or less...

 

[IVX]

capslock, it could be relatively expensive, about $200 or so, and I afraid if under my brand E1DA it will be popular. 100-150 range should be fine I believe.

 

[IVX]

But of course, I thinking about that too. Look, I can offer some analog-processing "adapters" like 1kHz(or another fixed F, 10kHz, 20kHz) notch filter within $50(in the standard case see attached) to extend THD+N resolution down to -126db i.e. outperform 1.5 times APx555. The same thing with 60db low-noise preamp, which outperforms noisy APx555 easily(6-8 times!). Actually, I hope AP's management will wake up soon and offer these adapters too, otherwise car-range priced device will be shamefully outperformed by microwave-oven-range priced ADCs. If I was AP I go to make near to impossible things for such price, for instance, it is possible to use a cooled ultralow-noise input stage to be unbeatable by a few dollars opamps and to be ready for any modern DACs tests.

 

[chris719]

But of course, I thinking about that too. Look, I can offer some analog-processing "adapters" like 1kHz(or another fixed F, 10kHz, 20kHz) notch filter within $50(in the standard case see attached) to extend THD+N resolution down to -126db i.e. outperform 1.5 times APx555. The same thing with 60db low-noise preamp, which outperforms noisy APx555 easily(6-8 times!). Actually, I hope AP's management will wake up soon and offer these adapters too, otherwise car-range priced device will be shamefully outperformed by microwave-oven-range priced ADCs. If I was AP I go to make near to impossible things for such price, for instance, it is possible to use a cooled ultralow-noise input stage to be unbeatable by a few dollars opamps and to be ready for any modern DACs tests.

AP probably hasn't had to think about hardware too much until recently. They satisfy most of their market with the capabilities of APx555. It's really all about paying for software, convenience, and a known level of performance.

 

[IVX]

chris719,
that's why I pushing my coder to start Windows FFT project to provide precision measurement Cosmos users
Yes, we can use a few free FFT apps for Windows but no one of them matched vs AP results and each other too. I believe I tried all, and no one correctly calculates noise or THD+N.

 

[Blumlein 88]

chris719,
that's why I pushing my coder to start Windows FFT project to provide precision measurement Cosmos users
Yes, we can use a few free FFT apps for Windows but no one of them matched vs AP results and each other too. I believe I tried all, and no one correctly calculates noise or THD+N.

Within the capabilities of whichever device is used, what is wrong with how REW calculates its numbers? I have noted their sweep numbers don't match their static test tone results.