Editing DI unit (section)

==Purpose==
There are two related purposes for a direct box: audio and electrical. The audio purpose is to deliver a clean, unaltered instrument signal to a mixing console or recording device, where it may be processed using other devices (equalization, compression, modulation, reverberation, etc.) to meet the needs of the audio production. Without a direct box, an instrument or microphone needs to be connected to an amplifier, which might then be connected to a speaker, another microphone, and then to the mixing console. These electronic stages and cables can color the sound in ways that some audio engineers and musicians find undesirable. Of course the reverse is true—many times musicians and audio engineers seek this coloring because it fits the style of music or recording. 

The electrical purpose of a direct box is to [[impedance bridging|bridge]] the impedance of the input and output. Most electronic instruments and microphones cannot be plugged directly into the pre-amplifier inputs of mixing boards or recording devices because of [[Impedance matching|impedance mismatch]]. Instruments are typically high impedance, whereas microphone inputs are low impedance.

The direct box takes a high impedance, unbalanced signal and converts it to a low impedance, balanced signal.<ref name=":0">{{Cite web|url=https://www.behindthemixer.com/direct-boxes-why-price-matters/|title=Direct Boxes - What They Do, Why They're Needed, and Why Price Matters|last=Huff|first=Chris|date=2018-07-12|website=Behind The Mixer|language=en-US|access-date=2019-03-22}}</ref> This allows the signal to be sent over long cable runs without signal loss, and greater rejection of interference due to the benefit of common mode rejection in a balanced signal.<ref>{{Cite web|url=https://www.prosoundweb.com/channels/church/church_sound_files_the_many_advantages_of_di_boxes/|title=Church Sound: The Many Advantages Of DI Boxes|last=Sokol|first=Mike|date=2016-07-13|website=ProSoundWeb|language=en-US|access-date=2019-03-22|archive-date=2019-03-22|archive-url=https://web.archive.org/web/20190322202635/https://www.prosoundweb.com/channels/church/church_sound_files_the_many_advantages_of_di_boxes/|url-status=dead}}</ref> Furthermore, it allows the low impedance signal to be sent to the input preamp of a mixing console which is designed to accept input from low impedance microphones.

Because all cables are capacitive, long cables used in live sound and recording can become a [[low‑pass filter]] which reduces the high end frequencies when used with high-impedance source.<ref name=":1"> {{Cite web|url=https://www.soundonsound.com/sound-advice/q-why-do-i-need-use-di-box|title=Q. Why do I need to use a DI box? {{!}}|website=www.soundonsound.com|access-date=2019-03-22}}</ref> Another advantage of DI units is that the DI contains a transformer to provide galvanic isolation that can eliminate a [[Ground loop (electricity)|ground‑loop]] hum.<ref name=":1" />