Radial ProDI DI box

Radial ProDI Passive Direct Box — Clean Signal Path for Stage and Studio

The Radial ProDI is a single-channel passive direct box that delivers instruments to a mixing console without hum, buzz, or distortion. A custom-wound Radial transformer provides 100% isolation between source and PA, eliminating ground loops. Because the design is fully passive, no batteries, phantom power, or external supplies are needed. The ProDI is the right choice for acoustic guitarists, bassists, and keyboard players who need a transparent, road-ready DI for live sound or home recording.

What Sets the ProDI Apart

Inside the steel enclosure, the ProDI pairs its custom transformer with an internal MuMETAL shield that blocks electromagnetic fields capable of distorting unshielded transformers. A military-spec PC board with a full surface ground plane reduces RF susceptibility, while isolated XLR connectors eliminate chassis ground potential.

Signal Handling — Headroom for Loud Sources

Active pickups and digital keyboards can overwhelm a passive DI, but the ProDI absorbs peaks without saturating. A switchable pad and ground lift give the operator two practical tools for live troubleshooting.

• Pad: -15 dB — tames hot pickups and prevents transformer saturation
• Maximum Input Level reaches +18 dB, so active bass and keyboard outputs pass cleanly
• Ground Lift: Yes — disconnects pin-1 to silence ground-loop hum

Audio Performance — Transparent Across the Spectrum

The transformer is wound for a flat, full-range response that preserves the natural character of acoustic and electric instruments.

• Frequency Response: 20 Hz – 18.5 kHz (±2.5 dB) — covers bass, guitar, and keyboard
• THD+Noise stays at 0.01% across the audible band, so the signal stays clean even at higher levels
• Input Impedance: 140 kΩ — minimizes loading on pickups

Connectivity and Construction — Built for the Road

A simple I/O layout makes setup fast, while the heavy-gauge steel chassis protects the internal electronics from touring wear.

• Inputs: 1x 1/4" TS unbalanced + 1x 1/4" TS thru — feed stage amp and PA simultaneously
• Output: 1x XLR 3-pin balanced, AES standard — long cable runs without noise
• Chassis built from 14-gauge welded steel in an I-beam layout, measuring 108 x 70 x 44 mm and weighing 540 g, protects the PC board from torque stress