Direct Injection Box. A means of taking a sound signal straight from an electronic instrument, such as an electric guitar, to the mixer of a sound system. The instrument is plugged into a jack socket in a small box which is connected to the mixer.
A small device that converts a high-impedance signal (such as that from a pickup) into the low-impedance signal needed to pass through long cables without signal loss. An active DI includes preamp circuitry that requires an AC adapter, batteries, or phantom power. A passive DI means that no power is required. A DI output is a low-impedance output (usually using a balanced XLR connector) on an amp or preamp, eliminating the need for a DI box.