Radial JDI DI box

Radial JDI — A Passive Direct Box Built for Honest Signal Transfer

The Radial JDI passive direct box sits at the top of the J-Class line and is designed to move instrument-level signals to a balanced mic-level feed without coloring or compressing the source. At its core is a Jensen JT-DB-EPC audio transformer that performs high-to-low impedance conversion and signal balancing across a magnetic bridge, passing audio while rejecting stray DC voltage. The result is the natural, pure sound of the instrument reaching the console with no hum and no buzz. Engineers and players who demand a transparent, dependable DI in any professional signal chain will find this model the right choice.

What Sets the JDI Apart in the Direct-Box Category

Inside the 14-gauge welded I-beam steel enclosure sits a Jensen JT-DB-EPC transformer with a smooth Bessel-curve character reminiscent of high-end vintage studio gear. A military-grade PC board is mounted on welded steel standoffs so it cannot shift under impact, virtually eliminating the cold solder joints that cause most DI failures in the field.

Transformer & Signal Path — The Heart of the Sound

The Jensen transformer is what gives the JDI its measured linearity and its ability to handle extreme signal peaks without distortion. Because the design is fully passive, no phantom power or battery is needed — simply plug in and the magnetic bridge does the work.

• Transformer: Jensen JT-DB-EPC audio transformer — passive impedance matching with high common-mode noise rejection
• Frequency Response: 10 Hz – 40 kHz — ruler-flat response with virtually zero phase deviation across the audible spectrum
• Fully passive by design, the unit operates without phantom power, batteries, or external supply, keeping the signal path clean from instrument input to console output.

Inputs, Outputs & Routing Features — Studio and Stage Flexibility

The I/O panel is laid out for fast, intuitive use under stage or console lighting, with switching options that solve common live-sound problems before they reach the desk.

• Inputs: 1 x 1/4" TS instrument input + 1/4" thru-put with Merge function — convert the thru to a second mono input for passive stereo-to-mono summing
• Output: 1 x balanced 600-ohm XLR, pin-2 hot (AES) — drives cable runs up to 1000 ft (305 m) with no appreciable noise
• An integrated -15 dB input pad and -30 dB speaker-emulation filter let you tame hot digital keyboard outputs or take a feed off a guitar amplifier post-distortion without overloading the next stage.

Onboard Controls & Build Quality — Built for the Road

Every switch on the JDI solves a real-world signal problem: ground lift disconnects pin-1 for 100% input-to-output isolation, polarity reverse flips pin-2/pin-3 to phase-match older non-AES gear, and the -15 dB pad manages loud digital keyboards and active bass pickups.

• Switches: Ground lift, polarity reverse, -15 dB pad, -30 dB speaker emulation, Merge — full toolkit for taming hum, phase, and level issues
• The 14-gauge welded I-beam steel with book-end design wraps the switches and connectors in a protective cage that survives typical stage abuse without flexing.
• Dimensions & Weight: approx. 50 x 89 x 140 mm, 1.0 kg — compact footprint with a full-bottom no-slip rubberized pad for amp-top placement

Who This DI Is For

This DI is purpose-built for live sound engineers, touring bass and keyboard players, worship band leaders, and studio producers who routinely run high-output instruments through long XLR cable runs. It handles active bass pickups, piezo-equipped acoustic guitars with built-in preamps, and wide-range digital keyboards without choking transients or introducing phase shift. At 1.0 kg with a full-bottom rubberized pad, the unit sits flat on top of a guitar amp without sliding during performance.