What Does a Direct Box Do for Guitar?
Updated Nov 13, 2026 · By 
Jonah Mercer · Editorial policy
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A direct box, or DI, takes the signal from a guitar and turns it into a balanced signal for a mixer or interface over a long XLR cable run. It sits between the guitar and the mixer, matching the signal so hum stays out, and it gives the guitar a thru jack to feed an amp at the same time.
What a DI does
A guitar puts out a high-impedance, unbalanced signal that loses strength and picks up noise over a long cable. A direct box converts that signal to a balanced, low-impedance signal that travels cleanly down an XLR cable to a mixer or interface. The balanced line resists noise along the run, so the guitar arrives at the desk the way it left the instrument.
Active or passive
An active DI needs power, while a passive DI needs none. The Samson MDA1 is active and runs on 48V phantom power or a 9V battery, and it has a 2-position 0dB/-15dB attenuation switch. The Radial ProDI, ProD2 and Pro DI are passive, and the ProDI and ProD2 list a 15dB pad switch. Passive boxes use a transformer instead of powered circuitry, and the ProDI lists a custom transformer with a 140kΩ input impedance.
Ground lift and pad
A ground lift switch breaks a ground loop that shows up as hum, and the MDA1 and the ProDI list one. The ProD2 lists a lift switch too. A pad switch drops a hot signal before it hits the mixer, and the MDA1 lists a 0dB/-15dB switch while the ProDI and ProD2 list a 15dB pad. Use the pad when the guitar signal distorts at the desk, and the lift when hum appears after everything is plugged in.
Connect it in order
Plug the guitar into the 1/4-inch input on the DI, and run the thru jack to the amp when you want the amp in the chain. Run a balanced XLR cable from the DI output to the mixer or interface input. Turn the gain down before you switch 48V on for an active DI, then raise it once the cable is in place. Check the ground lift and pad switches when hum or distortion shows up.
What you need
Samson MDA1 Mono Active Direct Box
An active mono direct box with a 0dB/-15dB attenuation switch, a ground lift switch and 48V phantom or 9V battery power.
- Ground lift
- Pad switch
- Runs on batteries
- 48V phantom power
- 2-year warranty stated
Liquid Audio Radial Engineering ProDI Bundle
A passive single-channel direct box with a 140kΩ input impedance, a 15dB pad switch, a ground lift switch and a mic cable in the bundle.
- Ground lift
- Pad switch
Radial ProD2 Passive 2 Channel Direct Box
A passive 2-channel direct box with an isolation transformer, a lift switch and a 15dB pad for a stereo guitar rig.
- Pad switch
- 2-year warranty stated
Radial Pro DI Passive Direct Box
A passive mono direct box with a custom transformer and rugged I-beam construction that handles huge transients without distortion.
- 2-year warranty stated
These come from our ranked list Best Direct Di Box, which compares them spec by spec.
Frequently asked questions
Does a direct box need power?
An active DI does, and a passive DI does not. The Samson MDA1 runs on 48V phantom power or a 9V battery, while the Radial ProDI, ProD2 and Pro DI are passive and need no power.
What does the ground lift switch do?
It breaks a ground loop that shows up as hum. The MDA1 and the ProDI list a ground lift switch, and the ProD2 lists a lift switch. Flip it when hum appears after everything is plugged in.
Can I plug a guitar straight into a mixer?
A direct box sits between them for that job: it turns the guitar signal into a balanced signal the mixer can take over a long XLR cable run. The thru jack still feeds an amp at the same time.
Ranked di boxes lists
More how-to guides
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