Unless something has changed very recently, I thought the MPC-X can act as an audio interface when connected to a computer, because it is USB class compliant. But it doesn't go the other way around. It cannot act as a "host" for a third-party class-compliant USB interface through the MPC-X's USB-A port. If I'm not mistaken, the USB-A port is for thumb drives only.
Have you successfully connected a third-party audio interface to MPC-X over USB?
I know that the MPC Live 2 has this capability.