Sampling cdistorte

So I have been using the MPC Ren for about 4 months, I like it a lot ( its my first experience with hardware). However, recently when I switched to my iMac, I can not sample using the headphone jack of my computer. When I have the input playing it sounds fine, but the second I switch it to comp, everything is delayed and distorted. Just downloaded the 1.8 software to no avail. I have the most recent firmware and drivers. Any clue?

I thought headphone was output only?

ya you must mean mic in. but why use that when you have the REN sound card?

I have a convertor from 1/8 inch to tape so I sample from my headphone jack in my imac as I would vinyl. Its also delayed/distorted with the mic in when recording guitar.