Control volume in Amarra using iTunes mode on a mac

[whodiini]

Has anyone tried to control volume in Amarra using iTunes mode on a mac?   I found that it depends on the equipment that is chosen as the output device in midi.

 

For most equipment, the volume control works.  But for Schiit devices, it is disabled.  (Eitr, Yggdrasil, Guginir,...)  Since the volume is controlled digitally by reducing the bit level, it would seem that it wouldnt matter which output device is used.  Has anyone else seen this and is there a workaround?

 

Thanks