I read this thread and thought it would be interesting to investigate power supply noise coming out of the RPi stock supply and USB outputs connected to the DAC.
Additionally, I developed a low noise linear power supply having two outputs – one to run the RPi and one to run the sink side of the USB output. This linear supply takes a 12 Vdc input, filters it, and then regulates it sown to 5.25 Vdc through two stages of linear voltage regulation.
Initial results are very positive, but I’ve got more work to do.
The analysis is fairly technical - hopefully I presented it in a way that is easy to digest.
https://1drv.ms/w/s!Am4mUJvVR_bzgcUpL_3HSnDwn2VbDw?e=hhMC6Y
Tom