I'm using it on Debian with pulseaudio. I have connected my phone via Bluetooth and can play music through it, but it's extremely quiet. The DAC's output goes into a Magni II Uber headphone amp which I have to turn up to almost max volume to hear anything. On any other input, this would blow my ears off.
I checked ever volume setting I could find in pulseaudio as well as in alsa, they are all on 100%.
Maybe related, I occasionally get the following error: "pcm512x 1-004d: no SCLK, using BCLK: -2"
Oh my god I feel stupid. I didn't notice that one of the sliders in alsamixer was a digital volume. I changed that to 100, now everything works.