An active direct box (DI) is an audio device used to convert high-impedance, unbalanced instrument or line-level signals into low-impedance, balanced signals.

These devices are commonly used in audio recording and live sound reinforcement to connect instruments, such as electric guitars or keyboards, directly to mixing consoles, audio interfaces, or amplifiers.
Active DI boxes provide several advantages over passive DI boxes, including signal amplification and impedance matching.

Input and Thru Jacks: Active DI boxes typically have two 1/4-inch input jacks. The "input" jack receives the instrument or line-level signal, while the "thru" jack provides a parallel pass-through connection for the unprocessed signal to be sent to an amplifier or other destination.

Balanced Output: The primary function of an active DI box is to convert the unbalanced input signal into a balanced output signal, usually via an XLR connector. Balanced signals are less susceptible to interference and can be transmitted over longer cable runs without signal degradation.

Active Circuitry: Active DI boxes are powered devices, often using batteries or phantom power provided by a mixing console or audio interface. The active circuitry in the DI box allows it to provide signal amplification and impedance conversion.

Ground Lift: Many active DI boxes feature a ground lift switch, which can help eliminate ground loop hum by isolating the ground connection between the input and output.

Pad (Attenuation): Some active DI boxes include a pad switch that allows you to attenuate (reduce) the input signal's level, making it suitable for high-output instruments or line-level sources.

Phase (Polarity) Inversion: Some active DIs offer a phase inversion switch, which can be helpful for addressing phase cancellation issues when multiple sources are mixed together.

Low-Cut (High-Pass) Filter: A low-cut filter (often switchable) can be present in some active DIs to reduce low-frequency rumble or interference in the signal.

Robust Construction: Active DI boxes are typically built to withstand the rigors of live sound and studio use. They often have durable metal enclosures and reliable connectors.

Wide Frequency Response: Active DI boxes are designed to faithfully reproduce the full frequency range of the input signal, ensuring accurate audio representation.

Versatile Applications: Active DI boxes are used with various instruments and audio sources, including electric guitars, bass guitars, keyboards, electronic drums, and line-level devices like audio interfaces and playback equipment.

Active DI boxes are valuable tools for audio engineers and musicians because they allow for clean, noise-free signal conversion and integration of various audio sources into a professional audio system.

They are commonly found in recording studios, live performance venues, and sound reinforcement setups. When choosing an active DI box, consider the specific requirements of your instruments and audio sources to ensure compatibility and optimal signal quality.

Active Direct Box
DigiPro Pro DI2