Most keyboard amps are equipped with input jacks for the instruments, cinch jacks for the aux-ins (CD, MD, MP3) and an XLR input for microphones. Higher quality models provide instrument inputs in a symmetrical design, which should, so long as the instruments also send their signal symmetrically, significantly reduce interference. Output wise most amps offer a symmetrical line-out or DI-out through which, for example, a hall mixer can receive the keyboard signal. Which is an extremely useful function if the amp is being used only as a personal monitor and not to reinforce the sound for the audience.
Often a connection for a foot pedal to be used as an effects control is included and some amps come with a headphone output. A more special feature are the so called link-connectors, with which some models – if there are two available – can be combined to create a stereo setup.