DI

Use a DI when you want to connect two devices and you have any of these issues:

• impedance mismatch
• line level mismatch
• differences in wiring or connectors (e.g. Balanced XLR to Unbalanced 1/4" Tip-Sleeve)
• noise - especially "hum" (ground loop)

A DI unit or DI box is an electronic device designed for connecting a piece of equipment with an electronic audio output to a standard microphone or line level input. It performs both level and impedance matching to minimise both noise and distortion. DI is variously claimed to stand for direct input, direct injection or direct interface. DI units are extensively used with professional and semi-professional PA systems and in sound recording studios. -- Wikipedia

You will also see the term DI used to refer to devices used to modify the tone as well as other properties of a signal. This is often in the context of Acoustic Guitar and Electric Bass. In the picture above the first two are passive DIs used for solving problems. The others are all sold as DIs that also shape the sound.

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