@spockfish I’ve found this explanation from the Roon Hardware team on the DSP volume Device volume control
It seems that the DSP volume is done on the endpoint and not on the core, therefore requiring another 24bit -> 64bit -> Volume -> Dither to 32/24bits process. I’m not sure if this double volume levelling (i.e in core for the LUFS and in the endpoint for final volume) is compromising the sound quality. If I’m needing a fixed volume control (e.g. -5dB, which is what I need for 75db FS with the DAC at unity gain), would it be better to set the LUFS to a relative -5?