It’s generally accepted that the power supply plays an important role in the audio quality, especially since the power supply section of a Raspberry Pi 4 is not particularly well filtered. I can see why this would be the case for DAC HATs that draw their power form the Pi itself, but what about when using a separate DAC connected via USB using it’s own power supply? I’m wondering if anyone has any insights?
I have only one experience, not with a rPi but with a Odroid N2+ and bad PSU.
The noise generated due to this PSU did reach the DAC and amplifier.
It would likely depend on the USB receiver in the DAC. If it offers galvanic isolation and isn’t powered by the USB source, it may not make much of a difference. if your system has sufficient resolution, I think you will find a good linear/clean power supply makes a difference.