Usual setup: Raspi 3B Rev 1.2 with Volumio 2.777 -> iFi iPurifier 3 -> Audiolab M-DAC -> Musical Fidelity X-Can v3 -> Quad ERA-1
I recently swapped out my Raspi 3B for a Raspi 4 4GB in the above setup with a new 64GB Samsung micro-SD flashed with Volumio 2.777.
After configuration with the M-DAC and connecting via NFS v4.1 to my Synology NAS, I noticed that the sound quality was completely unlistenable. Any file played back had a regular white-noise click, roughly every second that would also move from one stereo channel to another. I tried all the USB ports and the result was the same. I always use fixed volume at 100% with no mixer.
Investigating further, I activated the M-DAC buffer display graph and this was flickering wildly all over the place, occasionally going up to 100% but mostly moving rapidly between 0 and 25%. The expected, correct behaviour for this meter is for it to sit nicely level around the 50% mark.
My sweet spot for Volumio buffer settings is 2MB / 30%. Changing these also had no effect and I was getting an error of “General settings could not be saved” when rebooting.
I had a look in the logs and enabled Live logging, but I couldn’t see anything out of the ordinary, although I was getting a connection error to do with MPD after changing USB port and I couldn’t get Volumio to play at all until I rebooted the system.
I took the SD card out of the Raspi 4 and put it into the Raspi 3 and connected back up again, and all was right with Volumio. The buffer meter moved gracefully up to the 50% mark and stayed there from the first track played.
I can only conclude there is a big difference in USB functionality / support between the two Raspberry Pi devices. Perhaps there is a kernel patch required? I had read that upgrading the firmware on the Raspi 4 might be a solution, but it appears that this can only be done when using a Raspberry Pi OS image.
Has anyone experienced this with their Raspi 4 / DAC combination?