Boss VF-1 Effect Processor

I want to use my vf-1 as a pre-amp for recording.  I'd like to plug 
everything (mic & guitar) into the vf-1 and let it's AD converter do 
the work only.  So, can I just buy an rca-style SPDIF connecter 
interface-card to record direct without buying an expensive sound 
card with expensive DAC/ADC's?  If so, where would i find such a card?

Thanks,
Mark