The E1DA Cosmos Stack: ADCiso and 2 APUs. An example of bad multichannel - Neil Young's 'Harvest' on DVD-A (2002), fixed in new Atmos mix.

E1DA Cosmos ADCiso Grade A center.
Cosmos ADC Prototype I've been using over the years to the left.

Readers here probably are aware that over the last few years, I've been using the E1DA line of devices, the Cosmos ADC, APU, and Scaler typically paired with PC-based software like Room EQ Wizard for most of my measurements, especially for the highest fidelity products like DACs. As a hobbyist exploring objective performance, there's obviously no need to spend thousands of dollars on devices like the Audio Precision (here's a peek inside the APx555B top-of-the-line model, around US$30k). Not enough return on investment unless one is doing professional product design and testing.

As usual, over time things evolve around here and since I needed an extra ADC for work-related purposes, I bought one of the newer E1DA Cosmos ADCiso Grade A to replace the prototype that Ivan sent me back in 2021 which I will repurpose elsewhere.

This post is mainly an update and comparison, refer to the original article on the Cosmos ADC for more details.

Using Victor's Oscillator as reference (1kHz, ultra-low distortion analogue sine generator). A quick peek at the APx555B Analogue & DAC Signal Generators @1kHz. And on playing music "for fun"!

Note the 2-pin power connector on the lower left.

As you've seen on the blog over the last year, I've been using the E1DA Cosmos ADC from Ivan Khlyupin for a number of measurements recently (early report discussed here). I remain quite impressed by the performance of this little device with some caveats (lower input impedance, individual unit idiosyncrasies including what "grade" device one has).

While the ADC comes pre-calibrated by E1DA and unless you really want to spend some time playing with it, one should probably just leave it alone. Nonetheless, it's pretty clear that this is the kind of device made by and for audio hardware geeks! ;-) One has the opportunity to use the Cosmos_Tweak Windows program to fine-tune the calibration by changing independent ADC 2nd and 3rd harmonic compensation amounts, SDM integrator setting, and digital filter for the ESS Tech ES9822 chip.

So then, for this post, let's spend some time in the area of calibration and see if we can tweak the ADC using the device above - Victor's Oscillator (US$57) - an ultra-low distortion, 1kHz analogue signal generator which comes pre-assembled and tested from Riga, Latvia. As you can see in the image, there are 2 single-ended RCA outputs, with volume control ranging from 300mVrms (-8.25dBu) to 2.7Vrms (+11.0dBu). Note that a 10kHz version (and other custom versions) can be purchased as well but for typical audio purposes, 1kHz is in line with human hearing sensitivity.