I am not sure the kernel normally installed on the Duo includes the USB audio drivers. But I suppose you should be able to build them yourself using the cross-compiler.
Can anyone from the Mod team confirm ?
Alternatively, if you have another computer/PC on the side able to run netjack2 and to handle your USB interface, you can make this work with the MOD. The option is available in the MOD.
See that thread : Netjack pluggin