Apogee Quartet is a professional, reference quality audio interface for Mac and iPad. It features Apogee's premium 24-bit/192kHz audio converters, 4 digitally controlled mic preamps and 6 analogue outputs, plus headphones. Apogee Quartet also has ADAT inputs, allowing the unit to handle up to 12 channels of simultaneous recording. The 6 analogue outputs can either drive multiple pairs of stereo monitors, or drive a 5.1 speaker setup - volume can be controlled via the volume knob on the Quartet. Apogee's converter technology, ultra-stable clock technology and jitter suppression combine to make this one of the best-sounding interfaces at any price point - a definite consideration for anyone who's prime concern is audio quality.Apogee Quartet also provides MIDI over USB allowing for connection to USB controllers or keyboards without having to use another port on your computer, or a hub.