USB cable from C5D to the USB port on your Air. And I don't think it works with the Nexus 5. At least my Nexus 5 doesn't work...with stock 4.4.2. The nexus recognizes an external DAC but no sound outputs. I'm not planning on using it that way so no big deal either way, just would be nice if it worked. It's just the stock android build that doesn't include the correct driver from what I understand. That's not a C5D issue either...it's every DAC. It will work however, if you just run a line from the headphone out to the "input" on the C5D or any other amp/dac for that matter.
[COLOR=0066FF]Ah okay @_@ thank you for letting me know in advance.[/COLOR]
[COLOR=0066FF]Well... that's unfortunate.
Would it make much difference if I connected C5D to my macbook air, though? Sorry... I don't know much about these stuff.
Q#2: I have asus xonar essence stx sound card on my desktop. I wouldn't need C5D for it, right?[/COLOR]