i think the 13,s have a single input/output port for audio,
i know headphones with a mic work,ie mobile ph h/phones,
you may find it hard to have a mic in,and a line out,at the same time,there is always usb audio pre amps tho,there not even that expensive,its actually better to use a pre amp when inputting mics/guitars etc,more balanced signal,
the 15/17,s have a separate audio i//o =minijack stereo,whereas the 13 has one single mini jack port,that shares both,[im pretty sure it does]