DI an acronym for a direct injecting system is a wonderful innovation in the audio engineering industry. The technology was first invented by Whirlwind in the 1980s and was used in recording studios at that time.
The term comes from the phrase Direct insertion or Direct injection and it refers to the process of capturing a signal without the use of a microphone.
The major component of a DI box is a step-down transformer. And with our basic idea of a transformer, we know that it consists of two or more winding. The ends of each coil of wire come out from the windings; are the input and output. The input is called the primary winding or coil, while the output called the secondary winding or coil.
When an electrical signal is passed through the primary winding, it creates a magnetic field around the winding. The field created then induces an analogous signal in the secondary winding, which appears at the output leads. when the primary windings are more than the secondary winding, it is called a step-down transformer because the signal level and impedance are lower at the output than they are at the input.
when the secondary windings are more than the primary winding, it is called a step-up transformer because the signal level and impedance are higher at the output; however, the is no power increase with respect to the input. The winding of the secondary transformer is used primarily to connect the microphones and guitars to the input level of the mic pre-amps and adapters of the Guitar.
The DI box basically creates balance in an audio setup. It converts unbalanced signals to balanced. They have the ability to merge instrument level input, matching their signal to an XLR mic input to make it easy to hook on the mixing console.
Balanced signals are signals coming from XLR connectors or a balanced stereo jack. These means the connectors with 3pins for instance; microphones. This connection is the safest as 3 connectors are employed (the ground, live and return). These method guards against interference. Like the name implies, balanced is just very balance
These signals are produced from unbalanced connectors like mono jacks and RCA connectors. The concept of unbalanced connectors comes into play when only a single connector and a ground is used in transmission. This cable connection comes with the challenge of noise and interferences.
Stereo jack Stereo jack
Mono jack RCA plug
Live Stage Mix
Most musical instrument like pianos and guitars come with unbalanced outputs and are vulnerable to noise, the DI box handles the challenges associated with the unbalanced output state of these instruments and converts the signal to balanced signal for the mix. This goes a long way to increase the productivity and neatness of the output on the main. It also blocks phantom power from the mixer so it wouldn’t interact with the connected device.
Recording studios
In recording studios, the DI box is employed as a bridge between the instrument and the console because of lifeless output that is experienced if such instrument is directly plugged into the mixer. To check this challenge, the DI box matches the impedance and aids effective recording. The signal gains a lift.
Re-amping
This process involves taking a line level signal and converting it to an instrument level signal. It sometimes reduces speaker level signals to a mic level signal suitable for connection to a mic input.
There are basically two types of DI boxes;
Active DI's
Passive DI'S
Passive DIs
The most common type of DI box is the passive DI. It matches line level inputs or instrument level inputs to mic inputs. It has a transformer inside and two unbalanced input jack or RCA connected in parallel. Most engineers use this connection on bass guitar, where the bass is connected to the DI box before sending it to the stage amplifier for monitoring.
The processed signal comes out as balanced and the impedance is lowered so it can be transmitted in a distance to the mixer. The output of the passive DI box is mostly male jack port. The passive DI also comes with a ground lift which also helps battle unwanted sounds.
N/B: The passive DI box Reduced signal level typically from 3-6dB
Loss of tone with low-level signal Distorted when overloaded
Active DIs
The active DI requires power supplied through an internal battery and phantom power supplied by the mixer. The advantage of active DI is that it can be fine-tuned to produce a wide range of frequencies. The problem of disappearing low end encountered in passive DIs has been handled in the active.
N/B: The active DI box can distort too hot signals When the battery is drained or phantom power fluctuates.
