Talking about volume control:
Controlling the volume on the digital path is quite a non-sense operation.
This will reduce the digital resolution down from the original 16 bits. This means reduce the Dynamic and increase the background noise.
The digital output of the SoundBlaster works in this way... when i use it, i have to set the PC volume to the maximum before clipping and set the volume of the ampli to get the proper volume level.

The only way to avoid this problem on the EMPEG , is to use a ANALOG volume controller connected after the external DAC... it could be a active or a passive preamp.

I hope, anyway, that the digital output will be a fix-volume one… just after the CPU, like any CD player has.

P.S.
I do not think the EMPEG sets the volume on the digital path ... There is probably some where ... in the analog path of the signal, a gain controller. It could be inside the dac.