The Apogee Quartet Desktop Studio Interface & Control Center for Mac & iOS Devices is a USB 2.0 audio/MIDI interface, which enables you to record up to 12 channels of audio into an Apple computer, iPad, iPhone or iPod touch. It features four combo-XLR inputs and each one is equipped with a quality preamp for connecting microphones, instruments and line-level signals. The Quartet also features two optical inputs that support connection of additional eight inputs via an external ADAT lightpipe expander. The Quartet's rear panel has six analog 1/4" TRS line-level outputs, a Word Clock output and dual USB ports. One USB port is for connection to your Mac or iOS device and the other supports MIDI In/Out. There's also an intuitive volume/control knob, as well as two color OLED displays and multiple customizable backlit control buttons.