"Wotsa direct injection box?" we hear you ask, so let’s cut straight to the main chase. Basically, a DI Box is a device that accepts an unbalanced mono or stereo input signal from a musical instrument and converts it into a balanced output signal. This signal is then fed into a balanced microphone input on a mixing desk.

This has lots of advantages when it comes to minimising hum and noise, especially where long cable runs are involved. We’ll have more to say on this shortly.

The "direct injection" bit is a musician’s term. It refers to signals that are directly coupled (or injected) into the audio chain from a musical instrument, rather than picked up by a microphone. The signal can come from an outlet socket on the instrument itself, from a pickup (eg, on an electric guitar), or from any other source such as a CD player or tape player.

In a nutshell, a DI-Box allows musical instruments to be coupled to the balanced microphone inputs of a mixing desk. It has a high-impedance input so that it doesn’t load (or degrade) the signal source and a low output impedance, similar to that provided by a balanced microphone.

In fact, it’s fair enough to say that a DI-Box "looks" just like a microphone as far as the mixing desk is concerned.

Main Features High-impedance mono input (for guitar pickup) Stereo input mixing for tape, CD or other stereo signals Input level control, allowing optimum signal level before overload Balanced output Three-band equaliser (EQ) Can run from battery, plugpack or phantom power Battery check function Ground lift switch for hum loop control Housed in a rugged metal diecast case