27" 2010 iMac. I have a USB DAC. When using in TDM volume comes out of iMac speakers but if I press volume up/down it goes through USB DAC so I cannot change the volume. Anyone have any ideas? I would like the sound go through the DAC and into my external speakers while in TDM preferably but at the very least if I could at least control the volume of the input device while in TDM that would be nice.