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Radial Engineering JDI

Passive DI for acoustic guitar, bass and keyboards - Industry standard

Free Tech Support


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The Radial JDI is a passive direct box designed to handle extreme signal levels without distortion of any kind. Unlike an active DI that is limited by the buffering amplifier’s rail voltage, the JDI employs a Jensen audio transformer as the engine. Jensen transformers are legendary in their ability to gracefully handle transients while delivering a smooth, warm sounding Bessel curve, reminiscent of the finest vintage gear. Ruler flat from 10Hz to 40kHz and with virtually zero phase deviation, the JDI delivers the natural, pure sound of the instrument without artifact.

The 100% passive circuitry inside the JDI is incredibly efficient. The transformer performs both high-to-low impedance conversion and signal balancing at the same time with minimal loading and does so without any power whatsoever. The transformer also introduces a magnetic bridge that passes signal while rejecting stray DC voltage. This makes the JDI particularly adept at eliminating hum and buzz caused by ground loops.

Features include input and throughput ¼” connectors, -15dB input pad, ground lift, and 180º degree polarity reverse to help phase align the instrument with the PA. A secondary circuit is added for direct interfacing with high output devices such as guitar or bass amp loudspeakers plus a unique merge function allows stereo sources such as keyboards to be summed mono, saving valuable input channels.

Built tough to handle the abuse of live touring, the JDI features a 14-gauge steel I-beam inner frame and a unique book-end outer shell. The innovative design eliminates stress on the PCB, reducing opportunity for solder joints to go ‘cold’ while the outer shell creates a protective zone around the switches and connectors. The steel casing resists noise-causing electromagnetic pollution and the transformer’s sensitive inner workings are further protected from magnetic fields with a MuMETAL® can. This ensures the signal transfer is quiet and free from hum.

These combined features have made the Radial JDI the most popular passive direct box in professional touring and an excellent choice for instrument interface in the studio!

The Radial JDI… the world's finest passive direct box.


Virtually zero phase & harmonic distortion

Eliminates hum and buzz from ground loops

Jensen Transformer equipped passive DI

Exceptional signal handling and noise rejection


Input Connections1 x 1/4" TS phone
Output Connectors1 x XLR1 x 1/4" TS phone Thru
Input Level+19dB
Output LevelNot specified by manufacturer
Controls-15dB padPolarity reverseGround lift switchMerge of Input and ThruParallel 12" speaker emulation switch
Frequency Response10Hz to 40kHz
NoiseSNR: 119dB
Dimensions (WxDxH)6 1/2" x 4" x 3" (shipping)
Weight1 .92 lbs (shipping)
SpecialtiesMerge function converts the input and thru output jacks to left and right inputs and mixes them to mono at the XLR
Package Weight1.88 lb
Box Dimensions (LxWxH)6.6 x 4.2 x 3.1"