The MPC Series supports the use of a class compliant USB audio interface, to expand the input and output capabilities of the device when in standalone mode.
It is important to note, that class-compliant would mean that no drivers are required for the interface to be used or recognised by the MPC. If it has drivers for one operating system, but not for others, full functionality would not be guaranteed.
Once connected to the MPC, you can choose this as the audio device under the audio tab, in the preferences. If supported by your interface, you can also choose to enable up to 32 inputs/outputs, by ticking the matching box in the same preferences window.
Then, in the channel strip for each track, you can select which output you would like to route to on the interface.
For more information on setting up a class-compliant interface with an MPC, please see the below video: