depends what sort of soundcard you have, mine goes rca from rec output in mixer to the soundcard then there's a usb from the soundcard to the laptop but some of them have an aux input in them so I guess its rca from the rec output to aux in the usb and then you change which input you want to use when in ustream, hope that makes sense, its early.
cheers mate, i have the same setup yeah rca to record on mixer > usb to laptop. ustream has recognised the sound card as a setting but getting no sound when i stream