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Collaboration, Voice & AV · Intermediate

Direct Input Box (DI box)

A device that converts unbalanced high-impedance signals to balanced low-impedance mic-level signals for long runs.

Definition

DI boxes connect instruments and consumer sources to professional mic inputs, providing impedance matching, balancing and often a ground lift to break ground loops. Passive DIs use transformers; active DIs use electronics powered by phantom power or batteries.

Example

A keyboard's unbalanced output feeds a DI box, which sends a balanced signal to the stage box.

Exam tip

DI boxes solve level, impedance and balancing in one device.

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