Mac Mini USB output failing at 24bit

[drstrangequark]

Hello — I have a Mac mini 2012 connected by usb to an Emotiva TA-100.

The audio-midi settings app allows for 24bit output to be selected for the Emotiva, at various sample rates.

However, there is no audio coming through for these settings.  The 16bit options do pass audio, at various sample rates.

Any suggestions or common experiences?

 Thanks much for any thoughts. 

[drstrangequark]

Weird ...

If I set the Emotiva INPUTS to external line at 16 bit in the Mac Audi MIDI Setup (I’m not actually interested in using the TA-100 as an input device to the computer or my DAW in the least), then the outputs from the computer to the TA-100 will function at 24 bit, which is all I care about.

If anyone has comments as to why this might be, I’d love to hear them for pure curiosity, although my primary application issue seems to be resolved.

Thanks!

[drstrangequark]

Also, if anyone can replicate this behavior on another Mac, it would be interesting to see.