@IVX kindly sent me a sample of the new Cosmos ADC to try out. Here are my impressions of it so far.
The Cosmos is housed in a compact metal case with rubber feet, USB Type C connector on one and dual XLR inputs on the other. Power is over USB only. Beside the USB connector is small LED that flashes slower or faster to indicate the current sample rate. Two LEDs next to the XLR inputs appear to indicate presence of a signal. The input sensitivity is set by a bank of DIP switches on the bottom of the unit.
On the USB side, the Cosmos appears as a 2-channel input device with the usual sample rates up to 384 kHz and a choice of 16-bit, 24-bit, or 32-bit sample size. The ALSA mixer interface presents two gain controls and a toggle which somewhat confusingly select between stereo and mono mode, the latter providing a (theoretical) 3 dB reduction in noise level.
Unfortunately, I do not have a signal source clean enough to test the true performance of this ADC. Some useful information is nevertheless possible to obtain. Firstly, we can look at the recorded spectrum with no signal.
Aside from a slight DC bias, this is as clean as it gets. There is not a hint of USB packet noise or power line hum. Above 100 kHz, we do get a rising noise level from the sigma-delta modulator. There is also a very slight noise spike near 156 kHz.
Recording the same signal on both channels, the levels match to within 0.01 dB, much better than most DAC outputs.
Just to get another graph, here's the spectrum of a 1 kHz tone played on a cheap audio interface, though this obviously says more about the DAC than the ADC:
The Cosmos ADC does have one drawback in that the input impedance is relatively low, ranging from 640 Ω to 3.5 kΩ (measured at 1 kHz) depending on the the sensitivity setting. This may be too low for some sources.
That's all I have for now. I'll update if I think of any more relevant tests to perform. Suggestions are of course welcome.
The Cosmos is housed in a compact metal case with rubber feet, USB Type C connector on one and dual XLR inputs on the other. Power is over USB only. Beside the USB connector is small LED that flashes slower or faster to indicate the current sample rate. Two LEDs next to the XLR inputs appear to indicate presence of a signal. The input sensitivity is set by a bank of DIP switches on the bottom of the unit.
On the USB side, the Cosmos appears as a 2-channel input device with the usual sample rates up to 384 kHz and a choice of 16-bit, 24-bit, or 32-bit sample size. The ALSA mixer interface presents two gain controls and a toggle which somewhat confusingly select between stereo and mono mode, the latter providing a (theoretical) 3 dB reduction in noise level.
Unfortunately, I do not have a signal source clean enough to test the true performance of this ADC. Some useful information is nevertheless possible to obtain. Firstly, we can look at the recorded spectrum with no signal.
Aside from a slight DC bias, this is as clean as it gets. There is not a hint of USB packet noise or power line hum. Above 100 kHz, we do get a rising noise level from the sigma-delta modulator. There is also a very slight noise spike near 156 kHz.
Recording the same signal on both channels, the levels match to within 0.01 dB, much better than most DAC outputs.
Just to get another graph, here's the spectrum of a 1 kHz tone played on a cheap audio interface, though this obviously says more about the DAC than the ADC:
The Cosmos ADC does have one drawback in that the input impedance is relatively low, ranging from 640 Ω to 3.5 kΩ (measured at 1 kHz) depending on the the sensitivity setting. This may be too low for some sources.
That's all I have for now. I'll update if I think of any more relevant tests to perform. Suggestions are of course welcome.
. So one needs to add a DC filter in the digital domain to get rid of this DC offset - it seems. If anyone knows differently please tell.
