E1DA Cosmos ADCiso Review

[KSTR]

Even with 1%, I don't see how they could be that different.

I've been wondering, too.

Unequal source (output R) loading of the two legs to ground in SE/mono.

That does not explain the channel to channel difference

Theoretically, the SE input impedance, based on (assumed!) 499R input and feedback resistors on the FDA would be 666R, just like @pma found as well.

But the input is AC-coupled so an AC impedance measurement must be used, and that might have gone slightly wrong between channels?

 

[pma]

But the input is AC-coupled so an AC impedance measurement must be used, and that might have gone slightly wrong between channel

I used AC impedance measurement, of course. And L and R channel impedance was a bit (10%) different, as I wrote before.

 

[KSTR]

I used AC impedance measurement, of course. And L and R channel impedance was a bit (10%) different, as I wrote before.

I'll double check with my unit and report back.

 

[capslock]

I used AC impedance measurement, of course. And L and R channel impedance was a bit (10%) different, as I wrote before.

I have measured the outputs of my Motu M4 against ground with a True-RMS meter and found the + and - channels to be different by several 10s of mV. That might be down to resistor tolerance but it certainly was not in the 10% range.

 

[capslock]

This is the ADC hump thread btw.

ESS hump strikes back

Sorry I assumed because there was an AP logo in the graphs. How did you interface the Cosmos ADC to an AP? Via ASIO drivers.

www.diyaudio.com

 

[Watire]

Actually relevant for music recording/playback is the range from -10dB to -30 or -40dBFS. You never run an ADC close to clipping in practice.
Tests at 0dBFS are not very meaningful with regard to real life situation.

I understand. So we have to simply focus on the management of the source with the ratio between digital level and voltage output in the case of a DAC.
From my perspective a precision ADC helps to discover at which best operational level a device can be run. It makes it useful to a broad range of users even only to monitor AC hums on turntable. Cosmos is clearly high end use case so I would urge the common DAC manufacturers to follow on WiiM footsteps and add value to some of their devices with a quality ADC input.

 

[morillon]

I don't understand your point

I understand. So we have to simply focus on the management of the source with the ratio between digital level and voltage output in the case of a DAC.
From my perspective a precision ADC helps to discover at which best operational level a device can be run. It makes it useful to a broad range of users even only to monitor AC hums on turntable. Cosmos is clearly high end use case so I would urge the common DAC manufacturers to follow on WiiM footsteps and add value to some of their devices with a quality ADC input.

I don't understand your point...
the ADC of Wiim products is very modest, not even enob 16bits and just "just in case", see bring in a phono tuner tape etc.
(moreover the adc is a bit obligatory in these machines because there is no analog processing except the dac... therefore digitized to be num to ana afterwards.... on the other hand can be just interesting for transmitting in other rooms on other wiim machines etc)

 

[Watire]

I don't understand your point

the ADC of Wiim products is very modest, not even enob 16bits and just "just in case", see bring in a phono tuner tape etc.
(moreover the adc is a bit obligatory in these machines because there is no analog processing except the dac... therefore digitized to be num to ana afterwards.... on the other hand can be just interesting for transmitting in other rooms on other wiim machines etc)

The point is having a ADC is useful to monitor how your elements are behaving. Adding the function to differentiate is an option that WiiM initiated, purposefully in their context as you explained.

 

[capslock]

The point is having a ADC is useful to monitor how your elements are behaving. Adding the function to differentiate is an option that WiiM initiated, purposefully in their context as you explained.

I agree about the functionality. But Wiim put in an ADC that is adequate to digitize a phono pickup, a cassette tape or an FM tuner. It is not adequate to monitor anything at CD level or better.

 

[S G]

Not sure if it was mentioned earlier in the thread, but doesn't RME ADI-2/4 Pro SE use the same ADC chip?

If so, would it be expected to have similar performance? In the review I see Cosmos compared to RME ADI-2Pro, not SE, and if I understand correctly, SE and non-SE versions have different ADC chips.

 

[Roland301]

That's a very good question... and it could well be the results are slightly worse as the ADCs they use (AKM AK5394A, discontinued) are spec'd a bit worse than the ES9822pro.

Actually just tried this on APX555B.

• Balanced output -> loopback
• 4Vrms 1khz stimulus
• 20khz ADC bandwidth
• High Performance Sine Generator as source
• High Performance Sine Analyzer unchecked

With those settings I was getting ~116dB SINAD due to ADC harmonics.
With the "High Performance Sine Analyzer" checked I got ~121dB.

Not sure if there are any relevant hardware/setup differences between this and Amir's unit that might affect these numbers.

 

[KSTR]

Not sure if it was mentioned earlier in the thread, but doesn't RME ADI-2/4 Pro SE use the same ADC chip?

If so, would it be expected to have similar performance? In the review I see Cosmos compared to RME ADI-2Pro, not SE, and if I understand correctly, SE and non-SE versions have different ADC chips.

To my knowledge, all ADI-2 Pro versions use AKM chips, both for DAC(AK4490/4493) and ADC (AK5574), and that will not change.
Early ADI-2 DAC use AKM as well. Only current version of ADI-2 DAC use ESS.
ADI-2/4 Pro use ESS as well.

 

[KSTR]

With those settings I was getting ~116dB SINAD due to ADC harmonics.
With the "High Performance Sine Analyzer" checked I got ~121dB.

APx brochure (linked above) states:

So 116dB SINAD does match.
121dB with HPSA looks reasonable, too.

But SINAD/THD+N is not that useful for comparison as we want to know the individual contributions of noise and harmonics. A those distortion levels noise basically always dominates.
Could you kindly post 1kHz spectra with and without HPSA so we could compare to Amir's plot from the first post?

 

[S G]

To my knowledge, all ADI-2 Pro versions use AKM chips, both for DAC(AK4490/4493) and ADC (AK5574), and that will not change.
Early ADI-2 DAC use AKM as well. Only current version of ADI-2 DAC use ESS.
ADI-2/4 Pro use ESS as well.

I found this link: https://forum.rme-audio.de/viewtopic.php?pid=192562#p192562

Differences ADI-2 Pro to ADI-2/4 Pro - Brief Overview
...
ADC: Selected ES9822Pro for lowest THD, highest THD+N and SNR

I understand that ADI-2/4 Pro refers to ADI-2/4 Pro SE, as there are no non-SE models with 4 outputs listed on RME site.

 

[capslock]

@ Roland301: what happens with the harmonics when you go down -1 dB? My experience with AKM has been that they do best at -6 to -15 dB. What level works bests depends on the ADC and the front end.

@ KSTR: wow, they must have bought a stash before they went EOL.

 

[HpW]

Here some results as work/research (HW & SW) in progress ... as one liked to avoid any hum and nicer 1/f figures.
Any AN (amplitude noise) to come...

Note: ENF means "Enhanced Noise Floor"

Hp.

 

[capslock]

HpW, that looks good but is rather cryptic. Care to share more?

 

[weme]

Manufacturer	Model	Channels	Bandwidth	Analogue I/O	Digital I/O	Price $	Spec SINAD	Typ SINAD
Audio Precision	APx555	2	200kHz	Y	Y	30,000	117	120
E1DA	Cosmos	2	190kHz	Y	N	298	117	117
Audio Precision	SYS2722	2	80kHz	Y	Y	26,000	112	115
Stanford Research Systems	SR1	2	200kHz	Y	Y	17,000	109	113
Agilent / HP	U8903A	2	100kHz	Y	O	(6000)	108	110
Audio Precision	APx525	2-4	80kHz	Y	Y	27,000	108	110
Keysight	U8903B	2-8	80kHz	Y	O	28,000	108	110
QuantAsylum	QA403	2	80kHz	Y	N	600	105	110
Rhode & Schwarz	UPV	2-8	250kHz	Y	O	12,000	105	110
Audio Precision	APx516	2	80kHz	Y	Y	6,000	109	109
PrismSound / Spectral	dScope III	2	200kHz	Y	Y	4,400	105	108
PrismSound / Spectral	dScope M1	2	90kHz	Y	Y	4,400	105	108
Rhode & Schwarz	UPP	2	80kHz	Y	Y	(7000)	100	105
QuantAsylum	QA401	2	80kHz	Y	N	450	101	101

Nice idea to create an overview of these measuring systems with your table.
A suggestion to supplement the table:

A/D: Bandwidth | Input range [Vrms] | Impedance
D/A: Bandwidth | Output range [Vrms] | Impedance

Supplement with RME ADI-2/4 PRO SE
"33. Technical Specifications, page 70 | 34.9 ADI-2/4 Pro SE as Hardware I/O for Measurements, page 84"

For better readability, the table could be exported to a PDF file and made available here.

 

[restorer-john]

For better readability, the table could be exported to a PDF file and made available here.

Only if it is accurate, which it is not.

 

[KSTR]

Cosmos ADC Input Impedance, AC 1kHz, measured with LCR Reader MPA (a truly terrific device, despite the cheap looks).

Perfect match of L and R channels as expected (maybe @pma's unit has issues with the micro switches?) and in line with manufacturer's specification.
The grey values are for completeness only.