Direct Box

A direct box (often called a DI Box; short for “direct injection” box), is used to convert high impedance line level audio signals to low impedance mic level signals. Traditionally these devices have a female ¼” input, an XLR male output, and either a ¼” output or another ¼” jack that parallels the input jack. This secondary jack is often used to feed an instrument amplifier. A typical set up can be as follows: bass guitar plugs into the DI box, the XLR output of the DI box is plugged into a mixer, and the ¼” output is plugged into the bass player’s amplifier.
DI boxes often have additional features such as a PAD to reduce the signal strength of the incoming audio signal, and a ground lift switch. DI’s are available in passive and active varieties. Active DI’s require phantom power to operate.