A DI box is a device used to gain the correct signal level from a musical instrument. The output signal is split into several channels by a switchable attenuator. This circuit reduces the incoming signal by a fixed amount to avoid overloading the circuitry. Common pad settings are -15dB and -20dB. The -15dB pad is recommended for active pickups with high output and a -20dB pad is recommended for unbalanced line-level equipment.
Passive DI boxes
Passive DI boxes have come a long way since their invention in the 1960s. While most still feature single-channel outputs, more advanced models can accommodate up to eight channels. Passive DI boxes can be used to connect keyboards, electronic instruments, and computers to PA systems. Compared to active DI boxes, passive DI boxes don’t need power and can effectively eliminate ground loop noise.
Passive DI boxes use electromagnetic induction, while active DI boxes use a power source. Passive DI boxes work like a transformer by converting line-level inputs into low-impedance outputs. The difference between active and passive DI boxes is in their ability to balance and match signals. The impedance of the source signal will determine how much power is required to drive a passive DI box.
Transformers built into modern DI boxes
If you’re an audio engineer, you’ve probably heard the term “transformer” used in reference to direct-input jacks. These devices are used to eliminate ground loops, which are the culprits for a bad hum. These transformer-based DIs provide both electrical isolation and ground lift capabilities to eliminate these problems.
The best transformers have more than one primary winding. They have a higher secondary winding than the primary. This produces less distortion and a wider bandwidth, but they are more expensive and difficult to find in a DI box. These devices are often used in the input stage of mic preamps.
Modern DI boxes also feature an input-signal attenuation feature. This option reduces high-level signals, which can overload the transformer. Typical DI boxes provide up to 40dB of attenuation for line and speaker-level sources. This feature is especially important for valve amps, since too much input signal can cause them to break.
Their sound quality
The quality of a recording’s sound depends on many factors, including the equipment used for reproduction and the listening environment. For example, stereo processing, dynamic range compression, and equalization can produce significantly different sound than the original recording. The goal of the reproduction process may be to capture the audio as closely as possible.
This concept of sound quality is applicable to many areas of product development. By studying the acoustic properties of different materials, a prototype can be simulated to get a good idea of what it will sound like. Then, changes can be made and tested to see if they improve the sound of the prototype.
DI boxes are a versatile piece of studio equipment. They allow you to convert an unbalanced line-level signal into a balanced mic-level signal. This lets you use a balanced cable with an unbalanced instrument, such as a guitar. These boxes also provide a throughput output that lets you take two signals out of the box at the same time.
DI boxes are commonly used in concert venues and recording studios. The processed signal from the box is connected to mic level inputs on the mixing desk. It is then routed to the bass amp, which is used for on-stage monitoring.