Typically, depending on your pick-ups, guitars and similar instruments generate a “Hi-Z” signal. Z refers to impedance, which is a term used in low voltage DC electronics to describe the resistance to signal flow throw a cable or circuit. Think of it this way; If you are electricity traveling through a cable you would be like a track star running a 100 yard dash. If you were a signal traveling through a Hi-Z cable, you would be like a track star running a 100 yard dash but your lane is knee deep with maple syrup. A lot of resistance right? That’s what impedance is, and we measure it in Ohms Ω. Typically a “Line Level” signal from a your home theater receiver to your amplifier or similar devises will be around 270Ω to 600Ω, and you will find from 16Ω – 100Ω for headphone jacks. Your guitar or bass however will be about 7000Ω to 15000Ω. So that is a quite a bit impedance comparably. You may notice that your guitar or bass doesn’t sound very good when plugged directly into mixer channel without proper pre-amplification and it is for this very reason you need to implement DI Boxes into your signal chain.
Active Vs. Passive
There are two main types of DI boxes active and passive. Active DI Boxes use a power supply to process the audio signal what passive DI boxes operate off of attenuation of the circut to change the impedance of the hi-z instrument signal to a usable line level signal. The main functional difference between the two is that active DI boxes switch hit! Active DI boxes can convert Hi-Z Hi impedance signals to line level signals as well as convert line level signals into Hi-Z signals.
DI boxes are very popular for bass and guitar signals to record and or amplify a clean signal. This can be used on various other pickup equipped instruments as well as violins, standup basses, ect…
Another really handy application for an active DI box is “Re-amping”. When you record an instrument such as guitar, a very popular technique is to split the signal to both an amplifier that is mic’d up and a DI box clean to an open channel on your console/interface.
This results in both a keeper amplified guitar track to ensure you capture a genuine performance while you also have a clean guitar track that can be Re-amped giving you incredible flexibility in the studio. Re-amping is the process of routing the recorded clean instrument signal back to an amp using an Active DI box.
DI Boxes are crucial for the best possible sound in the studio and on stage so be sure you include a few in your audio arsenal.