ALSA error

[Steven Crook]

Discovered USB devices are kept in the MPD list to allow switching between HDMI, Headphones and USB, and also if the USB device happens to be unplugged or powered off it can be plugged back in or powered on and its config will be intact.

This works perfectly fine with most USB Audio devices but with your particular device there appears to be a hardware or cable issue that is causing the device to intermittently be unrecognized by Linux/ALSA after power up.

The MPD cache is what I'd assumed to be the case. I think a cable fault is really unlikely, I've tried three different cables, it makes no difference. Hardware faults tend to be either there or not, and  I'm not moving anything so I doubt it's a loose connection. I'd wondered if there was more up-to-date firmware that would fix issues in the USB subsystem, but AFAIKT the firmware comes with the distribution. That so?

The fact that the DAC and Pi can talk happily makes me think it's a software issue either in Alsa/MPD or DAC. Protocol issues in USB comms. But beyond that I really don't know. I still don't have enough to take to Schiit and have them spend time on it, particularly when they've got a shiny new USB interface they can say is flawless.

I spent a few hours going round in circles with Alsa trying to see if there were diagnostics I could get out of it for its chatting over USB. Eventually I decided I'd put in enough time and effort, and there were other, more enjoyable things I could be doing. Like listening to music. So I dug up the HiFi Berry Digi+ I've had hidden in a box. It works of course. But not being able to use USB still irks me

Anyway. I'll try USB as each new release and will post back here if things change. I have plans to order a couple more Pi and I'll try those too. If I discover anything useful I'll post back here.