Go to /Applications/Utilities/Audio Midi.app and see if you can change the bit depth/sample rate for the USB port.
DAC doesn't recognize hi-res files
I'll start by saying I've only just downloaded my first album, the HD Tracks sampler A-Gon offered a few weeks ago. Brought it down in 24/192 WAV format and that's what my MacBook Pro identifies all the files as. My McIntosh C50's built-in DAC automatically adjusts for file resolution on the digital input. I connected the Mac to the C50 via USB cable, and the C50 will only recognize the files as 16/44.1 resolution. Can somebody tell me what I did wrong?