What Is a Direct Injection Box?
Updated Nov 12, 2026 · By 
Jonah Mercer · Editorial policy
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A direct injection box, or DI box, connects an instrument to a mixer or recording interface. It converts a high-impedance unbalanced signal from a guitar, bass or keyboard into a low-impedance balanced signal on an XLR output. That balanced signal runs over long cables to a mixer or PA with less noise and hum.
What a DI box does
An instrument such as a guitar, bass or keyboard sends a high-impedance unbalanced signal from a 1/4-inch output, which loses strength and picks up noise over long cable runs. A DI box converts that signal to a low-impedance balanced signal on an XLR output, which a mixer or PA accepts directly. The Bolanle DI box takes high-impedance instrument signals to balanced XLR outputs for connection to mixers, and the StudioMan PRO200 converts high-impedance unbalanced instrument signals into low-impedance balanced signals. Connect the instrument to the DI box input, and the XLR output to the mixer.
Passive and active DI boxes
A passive DI box uses a transformer and needs no power: the Bolanle box uses dual-channel passive transformers, and the StudioMan PRO200 needs no batteries or external power supply. An active DI box needs power and can add gain: the Rowin LEF-331 runs on a 9V DC adapter with a 6mA power draw, and the Pegcabac box is an active design for guitars, basses, keyboards and DJ equipment. Active boxes also suit instruments with hot outputs, since the Rowin gain control spans -20dB to +20dB.
Pad, ground lift and thru
A pad switch lowers a strong signal before it reaches the mixer: the Bolanle box has a -15dB pad, the StudioMan PRO200 has -20dB and -40dB pads per channel, and the Pegcabac box has a -15dB pad. A ground lift switch breaks the ground connection to stop 60Hz hum from a ground loop: the Bolanle, Rowin, StudioMan and Pegcabac boxes all have one. A thru or link output sends the unaffected signal to an amp or monitor while the XLR output feeds the mixer.
How to connect a DI box
Plug the instrument into the DI box input with a 1/4-inch cable, and run a balanced XLR cable from the DI box output to the mixer or interface. Use the thru output to send the same signal to an amp for monitoring on stage. If the signal is too strong for the mixer input, switch the pad on; if hum appears, switch the ground lift on. The Bolanle box also has a SUM/MONO switch that combines stereo signals to mono for a single amplifier.
What you need
Bolanle Passive DI/LI Stereo Direct Box
A dual-channel passive DI box and line isolator with a -15dB pad and a ground lift switch, that switches between DI and line isolator modes.
- Pad switch
- Runs on batteries
- 48V phantom power
- 1-year warranty stated
IOppWin Rowin LEF-331 Active DI Box Pedal
A mini active DI box pedal with a cabinet simulator, gain control from -20dB to +20dB, a ground lift switch and true bypass.
- Ground lift
- Pad switch
- 1-year warranty stated
StudioMan PRO200 2-CH Passive Direct Box
A 2-channel passive DI box with -20dB and -40dB pads per channel, a ground lift switch on each channel and a parallel link output.
- Ground lift
- Pad switch
Pegcabac Active Direct Box
A compact dual-channel active DI box with two 3-pin XLR outputs, a -15dB pad and a ground lift switch, for guitar and bass instruments.
- Ground lift
- Pad switch
These come from our ranked list Best Direct Injection Di Box, which compares them spec by spec.
Frequently asked questions
Do I need a DI box for a guitar?
A guitar connects to a mixer or PA through a DI box when the mixer input needs a balanced XLR signal. The box converts the high-impedance unbalanced signal from the guitar into a low-impedance balanced signal, and the thru output still feeds an amp for monitoring.
What does the pad switch on a DI box do?
The pad lowers a strong signal before it reaches the mixer, so active pickups, synthesizers and hot line-level sources do not overload the mixer input. The Bolanle and Pegcabac boxes have a -15dB pad, and the StudioMan PRO200 has -20dB and -40dB pads per channel.
Does a passive DI box need power?
No. A passive DI box uses a transformer and needs no batteries or external power: the Bolanle box works with passive transformers, and the StudioMan PRO200 needs no batteries or external power supply. Active boxes such as the Rowin LEF-331 run on a 9V DC adapter.
Ranked di boxes lists
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