Reply to S4 w/ Vinyl Quick Question

Hey fellow DJTT enthusiasts.
First post here and have a quick question about the S4.
I recently saw the video on DJTT of an S4 being used to control 2 decks in traktor while vinl was controlling the other two decks. In order to do this would i need any type of audio interface in addition to the S4 order w/ the free traktor scratch upgrade kit, or would I just need two turntables and plug them in directly into the S4.

Thanks for the help guys, I'm trying to finally figure out if a switch from xponent to the S4 would be 100% worth it with my goals in mind.
-B. Fierce