E1DA Cosmos ADC

[johny_2000]

Yes, it was an unbalanced connection, so the input impedance of the Scaler to the DAC was 100k ohms as you pointed out. The output impedance of the Scaler was 10 ohms and the input impedance of the ADC was 1.66k ohms.

Good setup. On par with AP analyzer for a fraction of the cost.

 

[HaveMeterWillTravel]

I've been playing with the ADC and scaler for a couple of weeks now. Thoroughly impressed.

I see a couple of posts above about the input impedance of the ADC. Interestingly I was going to comment on that topic, too.

Although I see why one wants to have high input impedance on testing equipment---i.e., to cover all kinds of DUT by providing essentially no load---, I do notice a disadvantage. Such high input impedance causes interconnect cables to be vulnerable to noise! Of course, in most cases the noise is way below audible levels. But these days we hobbyists measure these things not just from audibility concerns. We measure devices whose noise floors are extremely low.

For example, today I found that my very short (2 ft) Canare L-4E6S star quad balanced cables, used to connect a DAC to the Cosmos Scaler, was very finicky with their position (literally posture) relative to other cables. The effects were clearly shown on measurements---not a beautiful picture I'd like to see! Took some time to troubleshoot and finally find the culprit: the scaler's 200 kOhm input impedance. That made sense.

For testing modern devices, 10k - 20k Ohm should be high enough. I wish the scaler had selectable input impedance

It may drive the golden ears crazy, but you could always use a precision resistor in parallel with the input. That is common in the RF world if a device's input impedance isn't 50Ω.

What is the freq. resolution of the FFT?
A 10kΩ resistor @ 24C looks to have ~2.7 µV rms (-111 dBV) thermal noise over 44.1 kHz.

 

[HaveMeterWillTravel]

Good setup. On par with AP analyzer for a fraction of the cost.

Of course, the AP is a bit harder to blow up when testing amplifiers.

What is the SOTA for a similarly priced signal generator to measure ADC and analog circuits?

 

[johny_2000]

What is the SOTA for a similarly priced signal generator to measure ADC and analog circuits?

Based on @IVX own measurements, the E1DA #9039S USB Balanced DAC has performance on par or better than the AP signal generator.

THD+N@1kHz@0dbFS -126db averaged over 10 samples 32b/96kHz@10k 49MHz
THD@1kHz@0dbFS -140db typical calibrated with Cosmos APU 32b/96kHz@10k 49MHz.
THD@1kHz@0dbFS -145db typical calibrated with Cosmos APU 32b/96kHz@10k 24MHz

He also mentioned in his blog that the latest results show that there is a way to get all harmonics <-150dB.
Moreover, with the yet to be released Cosmos LPF, the #9039S->LPF combination has a balanced output with THD@1kHz -155dB and all harmonics at -160dB or less.

 

[HaveMeterWillTravel]

Based on @IVX own measurements, the E1DA #9039S USB Balanced DAC has performance on par or better than the AP signal generator.

THD+N@1kHz@0dbFS -126db averaged over 10 samples 32b/96kHz@10k 49MHz
THD@1kHz@0dbFS -140db typical calibrated with Cosmos APU 32b/96kHz@10k 49MHz.
THD@1kHz@0dbFS -145db typical calibrated with Cosmos APU 32b/96kHz@10k 24MHz

He also mentioned in his blog that the latest results show that there is a way to get all harmonics <-150dB.
Moreover, with the yet to be released Cosmos LPF, the #9039S->LPF combination has a balanced output with THD@1kHz -155dB and all harmonics at -160dB or less.

When I see such numbers my innate response is to call BS. Just shows how damn fast ADC/DAC technology has progressed in such a short period of time!

I'm going to have to explore these for other (non-audio equipment) purposes.

Can they be DC coupled? [pretty please]

 

[johny_2000]

Can they be DC coupled?

I'm not sure what you mean DC coupled. Describe or draw a diagram of the connections.

 

[HaveMeterWillTravel]

I'm not sure what you mean DC coupled. Describe or draw a diagram of the connections.

Oh. Ignoring the technical aspects, AC coupled essentially means it rejects or filters out DC signals. Basically a high-pass filter.
DC coupled generally means it's flat/usable for DC signals are slow varying AC signals.

I would say the classic example are oscilloscope inputs which often can be switched between the two.

 

[johny_2000]

DC coupled generally means it's flat/usable for DC signals are slow varying AC signals.

Here's what the E1DA #9039S DAC specs say about it:
Frequency response: DC-130kHz +.05/-3db @32b/384kHz, -.5db at 45kHz. DC performance is limited by DC protection.
For more information about DC performance you should contact the author.

#903*S | index

e1dashz.wixsite.com

 

[IVX]

Yeah, the USB bridge chip CT7601 has DC protection, it is possible to switch off with the special FW.

 

[narshorn]

Hello,

Just started using the Cosmos ADC iso with RIAA.
I use foo_record via foobar to get the flux stream sent into my system.

In foo-record I have 2 options, "Line" Cosmos, and "Exclusive".

I can choose up to 32bit float/192k in stereo mode, is there anything else to do to get to 384 option ?

I didn't install any drivers, W10 x64 recognized the device perfectly.

fbk 2.24.1 32bit version (to get the old 32 bit plugins to work).

Thanks for your replies,

Best regards,

n.

 

[staticV3]

Hello,

Just started using the Cosmos ADC iso with RIAA.
I use foo_record via foobar to get the flux sent into my system.

In foo-record I have 2 options, "Line" Cosmos, and "Exclusive".

I can choose up to 32bit float/192k in stereo mode, is there anything else to do to get to 384 option ?

I didn't install any drivers, W10 x64 recognized the device perfectly.

fbk 2.24.1 32bit version (to get the old 32 bit plugins to work).

Thanks for your replies,

Best regards,

n.

192kHz is likely a foo-record limitation.

You can open the sound control panel and check the available sample rates for the Cosmos there. It should show up to 384k regardless of which driver you use.

While 768k is possible with the Cosmos, 384k is the limit of Windows DirectSound.

You can try installing the Cosmos driver (Link), but I doubt that'll unlock higher sample rates in foo-record.

 

[narshorn]

Thank you !

I also asked about this on the foo_record thread on hydrogenaudio




I use Cosmos_tweak to switch the device to stereo mode.

However, it worked yesterday, but this morning it doesn't ! I don't have access to proper stereo mode anymore

Correctly connected and moving app slider to the left passes via "Digital RIAA", but only right channel is heard once slider at the left.

When I move again slider fully at the right, via 'RIAA bump' I get "unproper stereo", low gain on left channel.

How do I fix this issue ?

I started reading the threads but it seems make stereo mode default would be my target.

Best regards,

n.

EDIT : installed Cosmos driver as stated by IVX and restarted computer. Checked devices manager and all is fine with Cosmos ADC.

But same issue as before, only right channel playing by the Windows or Cosmos Tweak controls, or passing via RIAA bump, on the other side for the slider, stereo is not correct.

Maybe I am experiencing firmware issue. I have to check if the firmware installed is up to date. How do I proceed to check this ?

 

[DavidR]

I can't directly comment on your points. The one thing I can say is that when I have been switching the ADC mono/stereo at times it stopped responding. The solution was to disconnect the USB (at the PC to prevent damage to the USB C socket), then disconnect/reconnect the power cable and reconnect the USB afterwards. That evidently resets it. Might also be better to unplug the power device (I use an old phone charger) and give it time to drain. I seem to recall some saying that the USB C connectors can have issues, best to be on the safe side.

 

[narshorn]

I can't directly comment on your points. The one thing I can say is that when I have been switching the ADC mono/stereo at times it stopped responding. The solution was to disconnect the USB (at the PC to prevent damage to the USB C socket), then disconnect/reconnect the power cable and reconnect the USB afterwards. That evidently resets it. Might also be better to unplug the power device (I use an old phone charger) and give it time to drain. I seem to recall some saying that the USB C connectors can have issues, best to be on the safe side.

Thanks David, I did all as you said but problem is still present !

A last thing, I have to check that the problem doesn't come from my RIAA, otherwise I think my Cosmos ADC might be buggy

Still on hold to get info about readin firmware version and eventually re-flashing ...

Thanks for replies,

Best,

n.

 

[narshorn]

Pop-in just to say that my problem is solved !

It was a problem of loose connexion on the RCA cable between turntable and RIAA.

Now both channels play OK and balance is fine.

Best regards,

n.

 

[FrenchFan]

I leave here some measurements concerning the
phase between the 2 channels of the E1DA adc.

I had made measurements with the cross correlation.

REW having 2 correlation methods

1) cross correlation averaging
2) cross correlation averaging + cross correlation magn.

The first method is very sensitive to the phase between the
ADCs, but on the other hand faster to converge.

I did not find the precision great on the THD.

method "2" being approximately the average
of the THDs of the left channel and right channel of the adc, seems to me the
most "precise" method of the 2 methods.

Method "1" had some differences especially if
we applied a phase shift between the 2 signals
I had a case where H2 disappeared
(I guess cold was the cause)

Anyway I wanted to make sure that there was no
phase shift between the E1DA adc channels
(except maybe occasionally).

Here are my measurements, the conclusion is that there is no
shift between the ADC channels, it's almost
impressive.

So I generated a multitone signal of 60 frequencies
with a phase shift of 10° between each and
passed all of this through the pipe

 

[HaveMeterWillTravel]

What is the vertical scale for phase?
Are you able to plot the differential between the two phases at each frequency?

 

[FrenchFan]

I don't really understand what the vertical phase scale is.

I work in degrees, the phase is not
plotted but simply measured in the red list on the right
of the graph.

The phase is here the difference between the phase of the first
frequency and the others, H1 is at 0 degrees of phase

I give you the diff attached.

 

[Telemach]

Did you have a chance to compare E1DA to https://www.altor.co/products/test-equipment/usb-isolator ?

 

[Music1969]

@IVX a few mention Cosmos ADC has a lot of DC, which makes it not great for recording (like for null difference analysis)

Are you working on a newer Cosmos ADC? Maybe which has DC filtering?