I connected my Macbook to the DAC Magic via the USB input. The USB input is selected on the DAC Magic and the 44.1 indicator lights up to indicate that it recognizes the signal. but no sound comes out via both xlr and rca outputs! It does work however when i use an optical cable. I disconnected the usb cable from the dac magic and connected it to another device and hey presto, it works. Anyone knows why this is happening and can you please suggest a solution?