The XD series does not have a volume control. There is a volume up/down button on the remote, but the manual says it's for use with Esoteric amps.
There is also an app, Esoteric HR Audio Player, to play audio files on a computer. It may have a volume control, but I don't think that's what you're looking for either.
I would look into the Teac players. They may have volume control.