tsengf

Raspberry Pi 3 apparently has a bottleneck with their USB bus as multiple components shared it. If I remember correctly, ethernet is one of the components. Some folks have reported audio glitches when driving speakers from USB. I did not experience this issue on my rpi3 which was networked via wifi. However, on Raspberry Pi 4, I am experiencing a new issue that I did not experience on rpi3 with the R-41PM. There appears to be some quirk with the speakers that causes the linux sound system to think the speaker is "busy". More details here. http://tsengf.blogspot.com/2020/07/raspberry-pi-4-4gb-and-usb-audio.html I don't have an answer to your question re: USB vs optical. I suspect that digital is digital regardless of what transport mechanism. rpi4 has resolved the bus sharing issue.