6. Does the M9 support USB DAC? And how can I use it?

A: The M9 supports USB DAC for computers. To enable it, please enter the pull-down menu of the M9 and click the 'Storage' icon to change the mode to DAC, or go to Settings -> Audio and check the 'USB DAC' option. After that, connect the M9 to the computer via USB and use it as USB DAC. 

( Before using on Windows computers, you'll also need to install the DAC driver, and here is the download link: click here; for Mac computers, there's no driver required).

Here is the related instruction about how to install the DAC driver: click here