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E1DA Cosmos ADC

?? On the screenshot with nearly -150db of THD is the output of 9039S, DAC+HPA dongle.
Hi @IVX
I asked this from Archimago, and so far got no answer.
What is the USB source current drain for the 9039s?
I have ordered one, but I like to know from you.
No music current drain & music playing at almost full power average current drain.
Thanx
 
Hi @IVX
I asked this from Archimago, and so far got no answer.
What is the USB source current drain for the 9039s?
I have ordered one, but I like to know from you.
No music current drain & music playing at almost full power average current drain.
Thanx
around 150/650mA. Interesting that I roughly calculated the max power current first, and got 5V/((.7W+.7W)/.7) = 400mA(typical class AB amp efficiency is .7), 150mA+400mA = 650mA. Next, I measured that, and it was 650mA.
 
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around 150/650mA. Interesting that I roughly calculated the max power current first, and got 5V/((.7W+.7W)/.7) = 400mA(typical class AB amp efficiency is .7), 150mA+400mA = 650mA. Next, I measured that, and it was 650mA.
Thanx.
Wouldn't it be 550mA (400+150=550)?
Or you actually measured, and it was hitting 650mA?
So it is somewhat, headphone impedance related too. Say if it is not 16 ohm, but 25 ohm, then it is not outputting 700mW. Am I right?
And one last question:
Would a standard USB2 on a cellphone, provide that much current?
My sole usage would be, on the go, with my phone.
 
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Ah, it was early morning on my side, my bad, 550mA is calculated current, 650mA is actual. It was16ohm. Not everyone's phone may handle that but most, for instance, phones have 1A limit.
Thanx.
I was just reading the "extra bit of info" on your site.
So, to get so much power out, you have implemented an SMPS inside, to bump the supply rails to 6.25V?
If so, that answers a few of my questions, such as extra current drain, 700mW+700mW output possibility, if so, CLEVER!
Waiting for delivery now.
 
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Tried to fix the TINA-TI model to work with LTspice, but no luck. There were some illegal characters, netlist order was also different (to 1632) but there are syntax issues I could not resolve.

I'm reluctant to install yet another simulator....
Here is a working SPICE model for the OPA1633 if you still need it.
 

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  • OPA1633.zip
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the model is simplified, THD simulation shows -200db+ ;) MC12 model OPA1632 has a reasonable H3 -124db.
2024-09-21_15-50-30.jpg
 
the model is simplified, THD simulation shows -200db+
It is possible. As you probably saw, the library description:
OPA1633 - Rev. A
* Created by Ignacio Vazquez Lam; 2024-07-05
* Created with Green-Williams-Lis Current Sense Amp Macro-model Architecture
* Copyright 2024 by Texas Instruments Corporation
******************************************************
* MACRO-MODEL SIMULATED PARAMETERS:
******************************************************
* AC PARAMETERS
**********************
* CLOSED-LOOP GAIN AND PHASE VS. FREQUENCY WITH RL, CL EFFECTS (Acl vs. Freq.)
* COMMON-MODE REJECTION RATIO VS. FREQUENCY (CMRR vs. Freq.)
* POWER SUPPLY REJECTION RATIO VS. FREQUENCY (PSRR vs. Freq.)
* INPUT VOLTAGE NOISE DENSITY VS. FREQUENCY (en vs. Freq.)
**********************
* DC PARAMETERS
**********************
* INPUT COMMON-MODE VOLTAGE RANGE (Vcm)
* INPUT OFFSET VOLTAGE VS. TEMPERATURE (Vos vs. Temp)
* OUTPUT VOLTAGE SWING vs. OUTPUT CURRENT (Vout vs. Iout)
* SHORT-CIRCUIT OUTPUT CURRENT (Isc)
* QUIESCENT CURRENT (Iq)
**********************
* TRANSIENT PARAMETERS
**********************
* SLEW RATE (SR)
 
Hi all, not sure if anybody is still following this thread but I wanted to show you my Cosmos ADC + Scaler measurements as there is something wrong and I'm not sure if there is anything I can do or there is an issue with my Scaler unit. So I just received the Scaler this week and I was keen on testing it. I made my cables and I did some measurements on some DACs I have at home. I was surprised to see that the Scaler adds substantial noise. I then performd some ADC+Scaler noise measurements to see what is going on. The results are shown below:

1728750271093.png

As you can see, the Cosmos ADC has great noise figures. It's a "Grade A" device and I'm really happy with how it performs so far. But when I add the Scaler, things do not look so good. Even at the no gain setting the noise measured in REW is -108 dBFS A, considerably higher than the standalone ADC. I had a look here : http://archimago.blogspot.com/2022/11/early-look-e1da-cosmos-scaler-prototype.html and the results he reports (-121.6 dBFS A) at max gain (26dB) are much better that I have. The setup seems very similar to what I have. My setup is shown below:

WhatsApp Image 2024-10-12 at 12.03.53.jpeg


The ADC and Scaler are connected together with two jack to XLR cables I made. I then connected the input of the Scaler to the output of the D50s (not powered) so that it does not pick-up any noise form the environment. Both the ADC and the Scaler are powered from battery packs (one for each device).

Is there something I'm missing or doing wrong or is there an issue with the Scaler unit I got?

Any input is highly appreciated. Thanks!
 
I would recommend checking all your interconnecting cables for continuity and possible shorts with a digital multimeter. These 3.5mm and RCA connectors have very minimal gaps between the contacts under the outer shell. Measure them fully assembled.

Then, after double checking the cables, set the Scaler gain setting to 0 dB. Disconnect the RCA plug from the DAC, temporarily short the terminals of the RCA plug and repeat the noise floor measurements.
 
Hi all, not sure if anybody is still following this thread but I wanted to show you my Cosmos ADC + Scaler measurements as there is something wrong and I'm not sure if there is anything I can do or there is an issue with my Scaler unit. So I just received the Scaler this week and I was keen on testing it. I made my cables and I did some measurements on some DACs I have at home. I was surprised to see that the Scaler adds substantial noise. I then performd some ADC+Scaler noise measurements to see what is going on. The results are shown below:

View attachment 398362
As you can see, the Cosmos ADC has great noise figures. It's a "Grade A" device and I'm really happy with how it performs so far. But when I add the Scaler, things do not look so good. Even at the no gain setting the noise measured in REW is -108 dBFS A, considerably higher than the standalone ADC. I had a look here : http://archimago.blogspot.com/2022/11/early-look-e1da-cosmos-scaler-prototype.html and the results he reports (-121.6 dBFS A) at max gain (26dB) are much better that I have. The setup seems very similar to what I have. My setup is shown below:

View attachment 398368

The ADC and Scaler are connected together with two jack to XLR cables I made. I then connected the input of the Scaler to the output of the D50s (not powered) so that it does not pick-up any noise form the environment. Both the ADC and the Scaler are powered from battery packs (one for each device).

Is there something I'm missing or doing wrong or is there an issue with the Scaler unit I got?

Any input is highly appreciated. Thanks!
Hi horias2000

Your measurements are good.

The problem is that you did not consider
the input resistance of the Scaler (100Kohms),
which of course, makes noise.

Your measurement corresponds practically
to this case

Attached is the measurement of the Scaler with the input
open and the input short-circuited.
 

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  • answer.png
    answer.png
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When you DAC is plugged in, but not switched on like you are showing, there is no muting/shorting active on the output and the input to the scaler will be of variable/high impedance. Hence the noise.
 
OK, thank you all for the replies. I did another test with the inputs shorted (+ and - to GND) inside the jack connector that is inserted into the Scaler. The result are a lot better as you would expect:

cosmos+scaler_noise_2.jpg

The above image shows the ADC alone and then the ADC + Scaler with the input of the Scaler shorted. In this scenario, the noise is -127.4 dBFS A at 0dB gain and -123.3 dbFS A at 26db gain. This is much better than I initially measured. The input cable I used was single ended with one of the wires left in the air inside the RCA connector. I'll make a two RCA cable with the jack at one end and I'll make sure to connect both RCA on the DUT when measuring a single ended DUT.

Again, many thanks for your replies. Highly appreciated!

Horia
 
So I modified the cable by connecting the negative wire to GND. I then went back to my D50s and I performed some measurements. The results are a lot better. I get a THD+N of almost -111dB and this is only 3 dB shy of what Amir had. This is great!

cosmos_scaler_D50s_neg_to_GND_battery.jpg

I can even see on the plot when the display is ON and the difference between power brick :). Great success!
 
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