converter to mixer

i was wondering if i have a usb mixer can i connect an a/d converter to it or do i need a sound-card/interface with spdif??? :?:

Reuben, welcome; first, can you re-read/follow this http://www.johnlsayers.com/phpBB2/viewtopic.php?t=4060 Also, not enough info- there are too many devices with varying abilities to answer without knowing what you have. Some USB mixers ARE their own A/D converters (probably most of them) So, what do you have, and what's your plan so far? Steve