For DJs - How can I sample live from turntables?

How can I sample live from turntables and assign them to a pad? This would be used to take a sample form a song as it's playing and trigger the sample later in my set.

with one of the multiple outs on your mixer, run cable into inputs on mpc. then run stereo outs to channel input on mixer. in record mode turn monitor off so you dont get feed back and thenn youre good to go