The DI BOX

A DI (pronounced dee EYE) unit, DI box, Direct Box, Direct Input, Direct Injection or simply DI is an electronic device that connects a high impedance, line level, unbalanced output signal to a low impedance mic level balanced input on our mixers usually via XLR connector. DIs are frequently used to connect an electric instrument or a presenters computer audio to our mixing console's microphone input. The DI performs level matching (mic or line) and balancing to minimize noise, distortion, and ground loops. (previous text was lifted from wikipedia and slightly modified)

Here in AV we use 2 different DI boxes; One is the PROAV1 Multi-media DI made by Radial. The other is the dPDB (dual passive direct box) by ART. Both boxes have Ground lift and Attenuation. The ground lift helps rid your sound system of that annoying buzz that results from ground loops in the audio system. The Attenuation switch is there to help deal with a output from a device which may be to "hot"

The PROAV1 has a 1/4" in/thru, Stereo RCA in/thru, 3.5mm input and a +4dB Line XLR input. The +4dB Line XLR input can be turned on by depressing the XLR input select switch on the side of the box- A arrow points the way. The most common use for this box in AV is this: A presenters laptop is located more than 6' from your audio mixing board. laptop audio (unbalanced stereo output) goes into direct box, direct box uses balanced xlr output to run to mic input on mixing console.

The ART dPDB has two 1/4" in/thru's which can convert unbalanced mono signals to balanced mono which can be output on XLR cables.

Jeff's set up suggestion: Make sure that the laptops audio is set to roughly 50% so that the signal is not over or under driven when it gets to the board. To test your laptop audio level, play intended audio from laptop, set the gain on the mic (laptop) input channel so that it is hitting just under zero on the VU meter.

Next month...Press Boxes