DI Boxes

A DI unit, DI box, Direct Box, or simply DI (variously claimed to stand for direct input, direct injection or direct interface), is a device typically used in recording studios and PA systems to connect a high-impedance, line level, unbalanced output signal to a low-impedance microphone level balanced input, usually via XLR connector.

DIs are frequently used to connect an electric guitar, electric bass, keyboards and DJ mixers etc to a mixing console's microphone input.

The DI performs level matching, balancing, and either active buffering or passive impedance matching/impedance bridging to minimize noise, distortion, and ground loops.