DI Box - A direct box takes an unbalanced signal from a guitar, bass, or other unbalanced source and converts it into a balanced audio signal. i.e. an unbalanced guitar cord comes in, but balanced XLR (mic-style) cable comes out. To get the most from a direct box, your mixing desk must have balanced mic and/or line inputs Use a direct box if you are experiencing hum, buzz, or radio interference, or if your instrument's cable is longer than 20 feet. Keep the cord from your instrument to the direct box as short as you can and make up the rest of the run with a balanced XLR cable.