With an Asus Xonar Essence STU USB DAC the volume control is not working correctly in exclusive mode: the volume level is the same from 5 to 100. Lowering the volume to 0 mutes the sound completely.
I’m using the headphone output from the DAC. I don’t have a way to test the line output right now.
Changing integer mode doesn’t help. Disabling exclusive mode restores normal volume control in Roon.
DAC: Asus Xonar Essence STU
OS: OS X 10.10.5
Roon: 1.0 (build 30)
Source: Tidal, ALAC, MP3
Thanks @mike (and @brian) for the pointer and the clear explanation.
As an aside: anyone considering the Asus Xonar Essense STU for use with a Mac, you might want to keep looking. I haven’t been able to enable 192/24 for it. The Audio MIDI Setup tool only has 44/16 and 48/16 as available choices. Haven’t found useful Google terms yet for any tips.
For a Cambridge Audio DacMagic Plus the choices in Audio MIDI Setup include 192/24. (And get randomly reset back to 44/16 on reboot or kernel upgrade or some other event. Pays to have indicator lights on the DAC.)