STEREO I/O is a connection box that turns analog audio into digital signal. STEREO I/O has RCA plugs for use with virtually any audio equipment from DJ mixers to turntables, its other end has a USB connector for your Mac or PC. You can connect any line or phono-level gear to your computer for recording, mixing or processing. Or you can also use STEREO I/O as an output cable from your computer to inputs on an analog mixer, enabling you to mix MP3s and other music from a computer in your standard DJ mixer.