I use a Digi2 Pro board on my Raspberry Pi 3 running HifiBerryOS as a Roon bridge to send audio to my DAC via S/PDIF. I configured Roon to use Device Volume Control.
Now I want to understand what happens to the digital audio signal in terms of sound quality when I turn down the volume. AFAIK the Digi2 Pro is not capable of changing the volume in hardware. So it has to happen somewhere in the Alsa mixer. Is there any up or down sampling performed when changing the volume? Or does the software simply multiply the samples by a factor, e.g. 0.8, to reduce the volume to 80%?
My aim is to avoid any degradation in the signal path ('bit-perfect').