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IMO you could tell by checking the USB isochronous mode. Adaptive playback means the playback is clocked by the USB host controller. Then by principle it could not be synchronous to the incoming SPDIF stream. I have a similar soundcard and it has adaptive playback.

@Jukka : There are many other ARM SBCs with the necessary HW. Some have SW which already has all the needed parts to support your use case - e.g. https://www.audiosciencereview.com/forum/index.php?threads/using-orangepi-zero2-as-an-equalizer-between-usb-source-and-usb-dac.53750/

USB-A is a very interesting connector for OTG :-) Sometimes one needs to make one, for ugly hacking and testing, but to officially sell this...

CDSP can resample, but it must open the capture soundcard at some samplerate. Very few SPDIF input alsa drivers report the incoming samplerate as detected by the SPDIF receiver via dedicated alsa controls.

BTW https://github.com/raspberrypi/linux/pull/5751 https://github.com/raspberrypi/linux/issues/5748#issuecomment-1828330732

IMO the identification eeprom is just for easier (auto) handling of DTS overlays for hats https://github.com/raspberrypi/hats/blob/master/eeprom-format.md . Technically it's not necessary if you config your system manually for the given hat.

@MCH: That board looks simple. Those DACs have no I2C control. If that chip is EEPROM, probably just for hat identification as required by RPi specs?

Actually it's officially stated by MS: https://learn.microsoft.com/en-us/windows-hardware/drivers/audio/usb-2-0-audio-drivers#driver-development

The DAC chip has no MCLK output - https://www.ti.com/lit/ds/symlink/pcm5102a.pdf pin SCK is input only. But RP1 could be configured to output the MCLK clock used for the I2S interface. It's not exactly the PLL'd MCLK inside the DAC, but synchronous with the DAC. IIUC one can choose from...

It looks like the I2S driver is not correctly configured from device tree. It seems to be a problem of ubuntu only https://www.google.com/search?client=firefox-b-lm&q=designware-i2s+1f000a0000.i2s:+Missing+dma+channel+for+stream:+0 Maybe RPi has pushed some patch which ubuntu did not apply...

Are the driver + overlay already present in the Ubuntu kernel? It was added to RPi kernel in March 2024 https://github.com/raspberrypi/linux/commit/99e6cb05eaa2b133d9a2b7cb031fef2c19577cc1

Well, as you see those discussions, no new posts have been added. IMO it's safe to assume nothing has changed since then. The solution doing restarting CDSP (and therefore re-opening the device) instead of plain snd_pcm_prepare at XRUN is a reasonable method, nothing hacky. Recompiling CDSP on...

You do not have to use all channels, but the number must be between the min and max supported by the driver/device, as reported in the log. That's only 10 for the capture direction, in this particular case. Do you perhaps have the device switched to be clocked from incoming SPDIF, with no...

Is it actually possible? https://github.com/mikebrady/shairport-sync?tab=readme-ov-file#latency-stuffing-timing :

I agree, IMO the same effect is here - 120R of the mux vs. the 10k of the other resistor, times the mux THD => 0.2% THD * 0.01 ratio => some 0.002%, rough calculation. Absolutely inaudible. Yet IMO worse than performance of a good DAC chip. IIRC Ivan talked about using FETs as input attenuator...

I am afraid I do not understand. If a wire (zero resistance) has 0V potential against some common ground, such information does not say anything about a current running through that wire. A neutral wire from a 240V 2kW heater has zero voltage (against ground, you can touch it :) ) all the time...

Hm, please correct me if I am wrong. The analog mux is part of a voltage divider between outputs of U3A and U7A where U7A tries to keep its inverting input at virtual GND (i.e. equal to its noninverting input). To get 0V at the inv. input, a current must flow through the voltage divider, i.e...

@Frunse: Do you have any data to support those circuits would be better than the digital VC in your DAC chips? CD4051 analog switch has THD of 0.15% - 0.3% - check the datasheet. No noise figure, but I kind of do not think your circuit with so many resistors and opamps in the signal path will...

Very nice. Just a note - since the newer kernel has async UAC2 gadget, the CDSP config should enable rate adjust. CDSP will hit (sooner or later) xruns without that. If the gadget were adaptive (as in older android kernels), it would require rate adjust and async resampler.

Does your RPi airplay receiver or your airplay source have volume control? Maybe your RPi3 analog output is too weak for your amp. Easy to check e.g. with speaker-test -t sine - for details https://linux.die.net/man/1/speaker-test