What is a DI box and why do I need one?

A DI box is an impedance matching device, most commonly used to connect an unbalanced high impedance output signal from a guitar or keyboard, to a balanced low impedance input found on a microphone pre-amplifier. A DI box is equally common in the studio or at a live show. DI stands for direct injection, although direct input and direct induction are also commonly used terms. In a live context, sending a lower impedance signal over a long cable run, will significantly reduce signal loss and interference. This is because cables sending balanced signals, by design will eliminate interference and noise and maintain integrity in the sound quality over longer distances.

See image below for a typical studio technique for recording bass. You may also want to mic up the bass cabinet and blend this with the Direct Injection sound.

DI’s will be either passive or active, and there are good reasons and key differences between the two. Passive DIs have a transformer known as a bulan, and require no power to operate. This makes them a much simpler option. They may also have a Pad, ground lift and filter switches too. Passive DIs are less desirable for older instruments with much lower outputs. 

Some DI boxes have a particular tone, or colour that many musicians are after. The Acme Motown DI below captures that very desirable 60's tone. 

Active DIs include a pre-amp in their design. (NOT a microphone pre-amp) They require +48v to operate, which can either be supplied by a battery, or phantom power from the microphone pre-amp. Active DIs are generally more versatile, and capable of delivering a more detailed sound quality. In this context, a similar comparison could be made between dynamic microphones (passive), and condenser microphones. Some DIs also have a thru port, enabling a guitarist for example to send a signal directly to the console and the amplifier simultaneously.

Re-amping

Re-amping is the process of sending a balanced signal from your DAW (audio-interface) or recorder back to your unbalanced instrument amplifier. Essentially, a re-amping box is DI in reverse. The advantage here is, you can record all your guitar parts either dry or even incorporate software based FX, and then send them back through one or more guitar amps, recording the results via miking up the cabinets. This obviously minimises time with a session player, allowing you to perfect the recording afterwards. 

See, the humble DI box as an essential studio or live utility - you never know when one is going to save you bacon! 

See our range of DI's here!