What Is the Purpose of a DI Box?
Updated Nov 13, 2026 · By 
Jonah Mercer · Editorial policy
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A DI box connects an instrument to a mixer or PA system. It changes an unbalanced instrument signal into a balanced signal, and it cancels buzz and hum on the way. The 4 boxes below show the types: 1-channel and dual boxes for guitar, bass, keyboards and media players.
What a DI box does
A DI box sits between the instrument and the mixer. The Whirlwind IMP 2 is an in-line transformer that converts a line or instrument level unbalanced signal to a low impedance mic level balanced signal. The Pyle boxes do the same job as impedance transformers, and they add buzz and hum cancellation. The balanced signal then runs to the mixer or PA over XLR.
Match the input to the source
The input decides what the box connects to. The Pyle PDC21 and PDC22 take a 1/4 inch connector from guitar, bass, keyboards and outboard processors, and the Whirlwind pcDI takes 1/8 inch and RCA inputs from CD players, sound cards and MP3 players. The Whirlwind IMP 2 takes a line or instrument level signal. Check the plug on the source before you buy, since the pcDI is the box here for media players.
Use the ground lift and pad
A ground lift and a pad switch fix common problems. The Pyle PDC21, the Whirlwind pcDI and the Pyle PDC22 list a ground lift, which the Pyle bullets pair with buzz and hum cancellation. The Whirlwind pcDI adds a 20dB pad, and it also has a stereo/mono switch with XLR outputs. The ground lift and the pad are the switches for a buzzing signal.
Count the channels you need
Channel count decides how many sources a box takes. The Pyle PDC22 is a dual box with 2 channels, and the Whirlwind pcDI lists 2 channels with a stereo/mono switch. The Whirlwind IMP 2 is a 1-channel box. Count the sources before you buy, since a dual box covers 2 sources and a 1-channel box covers 1 source.
What you need
Pyle Premium Direct Injection Audio Box
A passive DI box with a ground lift, an input attenuator and hum cancellation, connecting guitar, bass and keyboards to a PA or mixer.
- Ground lift
Whirlwind pcDI Direct Box for Interfacing Outputs
A direct box with 1/8 inch and RCA inputs, a stereo/mono switch, XLR outputs, a ground lift and a 20dB pad for media players.
- Ground lift
- Pad switch
- 2-year warranty stated
Pyle-Pro PDC22 Dual Passive Direct Box
A dual passive direct box with 2 channels, a ground lift and a steel chassis, connecting instruments to a PA or mixer.
- Ground lift
Whirlwind IMP 2 1-Channel Passive Instrument Direct
A 1-channel passive DI box that converts an unbalanced instrument signal to a low impedance mic level balanced signal.
- 0.6 lb, the lightest here
These come from our ranked list Best Di Box, which compares them spec by spec.
Frequently asked questions
What does a DI box do?
It connects an instrument to a mixer or PA system. It changes an unbalanced instrument signal into a balanced signal, and the Pyle boxes add buzz and hum cancellation.
Do I need a DI box for a keyboard?
Yes, when the keyboard goes to a PA or mixer. The Pyle PDC21 and PDC22 connect keyboards, guitars and outboard processors to a main PA or recording mixer.
What is the difference between 1-channel and 2-channel DI boxes?
Channel count is the number of sources a box takes. The Pyle PDC22 and the Whirlwind pcDI have 2 channels, and the Whirlwind IMP 2 has 1 channel.
Ranked di boxes lists
More how-to guides
Product details come from each Amazon listing and can change. Check the listing before you buy.