Passive DI Boxes

A passive DI box uses a transformer rather than powered circuitry to produce a balanced signal, so it needs no power and its isolation breaks the ground loops that cause hum.

Shop passive DI boxes from SWAMP, Radial and ART. Transformer-isolated direct boxes that need no power, reject ground hum and handle hot signals on stage and in the studio.

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Shop passive DI boxes from SWAMP, Radial and ART. Transformer-isolated direct boxes that need no power, reject ground hum and handle hot signals on stage and in the studio.

About Passive DI Boxes

A passive DI box converts the unbalanced output of an instrument or line-level source into a balanced, low-impedance signal that can run long cable distances to a mixing desk without picking up noise. Passive designs use a transformer rather than powered circuitry, so there are no batteries or phantom power to worry about, and the transformer isolation naturally breaks the ground loops that cause mains hum.

The range spans affordable SWAMP passive DI boxes for everyday stage work through to professional transformer-based units from Radial, including the classic JDI and the dual channel ProD2 stereo DI, plus options from ART. Passive DIs suit keyboards, active basses and other strong signal sources; for low-output passive pickups, an active DI box is often the better match. Browse the full DI box range, or if hum is your main problem, a dedicated hum eliminator may be all you need.

Passive DI Box FAQs

How does a passive DI box work?

A passive DI box runs the incoming signal through a transformer, which induces a balanced, low-impedance copy of the signal on its electrically isolated output winding. No battery or phantom power is involved, and because input and output are isolated, a passive DI naturally breaks the ground loops that cause mains hum.

Is a passive DI box the same as a direct box?

Yes. DI stands for direct injection, and DI box, direct box and DI unit all refer to the same device. A passive direct box is simply a DI built around a transformer instead of powered circuitry.

When should I choose a passive DI box?

Choose passive when your source has a strong output, such as a keyboard, drum machine, active bass or audio interface. Passive DIs are also the safer choice where power is unreliable and the transformer isolation helps eliminate ground loop hum in complex stage setups.