Radial JDI Passive Direct Box

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Product Description

The Radial JDI Direct Box is considered by many to be the world's finest direct box. It is a passive DI that employs a Jensen isolation transformer for optimum audio performance offering outstanding linearity at all frequencies, combined with extraordinary level handling without introducing distortion. Being completely passive, the plug & play JDI does not require any powering and has the unique advantage of eliminating 60-cycle ground loops. This makes the Radial JDI a definite favorite with informed audio engineers. The JDI is great for guitars, bass, and keyboards and is particularly adept with high-output, broadband instruments such as active instruments and digital keyboards.


  • 100% passive design - no phantom
  • Jensen Transformer equipped
  • Dual function inputs w/2 channel merge
  • Polarity reverse switch
  • Speaker level input circuit
  • Ultra-durable welded steel chassis
  • Double sided printed circuit board
  • Protective channel for switches
  • Ground Lift and Pad switches
  • No-Slip bottom pad
JDI Features & Functions
The Radial JDI is a passive direct box that employs the world’s finest Jensen JT-DBE transformer as its main drive engine. The Jensen DBE transformer employs a laminated nickel core that has the distinct advantage of low-permeability. Permeability is a term that describes the metals ability to become magnetized and demagnetized without retaining any magnetic memory. When one considers that full bandwidth audio is made up of a series of fundamentals and harmonics that range from 20Hz to 20kHz all of which move in tandem, disrupting their relationship is not a desired effect! This underscores the importance of a very high quality transformer and Radial's decision to use a Jensen.
  • Welded I-beam construction makes it impossible to torque the PC board. This virtually eliminates cold solder joints - the No.1 cause of system failure in the field.
  • An innovative ‘slide-in-place’ XLR trace makes it possible to use I-Beam girder construction.
  • The JDI uses a Jensen transformer for distortion-free performance. The Jensen features a nickel core for best signal transfer and minimal loading.
  • A military-grade PC board is employed for maximum wear and tear in abusive environments. Welded steel standoffs ensure the PC board will not shift.
  • A -15dB pad allows super hot inputs such as that from a CD player to be connected and balanced for long runs.
  • The Merge function turns the input and thru into a passive mixer to sum stereo feeds to mono at the XLR output. This saves valuable inputs on the mixer!
  • The input connects to the instrument.
  • The thru-put is connected to the instrument amplifier. The JDI has a high input impedance to reduce loading.
  • Radial's book-end design creates a protective zone around the switches & connectors for best protection!
  • A heavy-duty baked enamel finish for excellent durability and great looks for years! 100% 14-gauge steel construction.
  • The XLR balanced mic level output provides 100% isolation for runs to 1000 feet without appreciable noise.
  • A polarity reverse switch flips the polarity from the AES standard Pin-2 to Pin-3 on the XLR and is used when combining sounds that may be out of phase.
  • The ground-lift disconnects the ground path to the transformer at the XLR output. This is used when a ground path is made at the input side such as with a keyboard.
  • The parallel speaker interface option introduces a second -30dB pad with band-pass filter to emulate a 12 inch guitar speaker.
  • A no-slip full bottom pad reduces mechanical vibration, improves electrical isolation and keeps the JDI from moving around on busy stages!
Using the JDI
Being completely passive, the Radial JDI is plug and play easy to use. Simply connect the instrument to the input, the amplifier to the thru-put and the mixer to the output and you are ready. The JDI input features a high 10kOhm input impedance for minimal loading. This makes the JDI ideal for interface with all instruments. The 600-Ohm mic level output allows the JDI to be used with typical snake systems that incorporate bridging transformers (splitters) without fear of overloading them. As a passive device, the JDI is particularly ideal for use with high output devices such as active or self-powered instruments such as acoustic and bass guitars with built-in battery powered preamps and keyboards. These devices tend to overload most active direct boxes making them sound thin and edgy. The JDI is capable of exceptionally high signal handling without distortion. The real benefit of isolation is immediately realized when connecting two pieces of gear together that are electrically powered systems. These typically employ different reference to ground voltage schemes which will often result in what is commonly known as ground loops or an annoying 60 cycle hum. The JDI’s exceptionally high common mode noise rejection completely eliminates this problem. This of course has the benefit of making stage set-ups quick and effortless.


The Radial JDI is Jensen Transformer equipped, high quality passive direct box that has the advantage of providing complete isolation for reduced noise. The exceptionally low phase distortion, almost perfect linear response and low harmonic distortion make the JDI a superb choice for critical recording or live performance. The rugged construction allows the JDI to be used in the most abusive environments without concern for damage. The Radial JDI Mk3 is ideal for acoustic guitars, bass, and keyboards.

warning WARNING: Cancer and Reproductive Harm -

Product Specifications


  • Dynamic Range: 135dB
  • Signal to Noise: 119dB
  • Maximum Input Level: +19dB
  • Frequency Range: 10Hz~40kHz
  • Linearity: 20~20kHz: 0.1dB
  • Phase Coherence:
    • 4º at 20Hz
    • 0º at 1kHz
  • Distortion at 20Hz: 0.006%
  • CMR Rejection: 100dB @60Hz
  • Input Impedance: 10kW
  • Output Impedance: 600W
  • Construction: Welded steel
  • Finish: Baked enamel
  • Input Connectors: Two 1/4 inch phone
  • Output Connectors: XLR male

Features and specifications are subject to change without notice.

Helpful Info about the Manufacturer
Phone:  604-942-1001 Warranty:  3 Year Transferrable
Joe Sanchez Submitted: 9/6/2018
Product Rating
This thing is awesome!!!
Product Rating
What is your opinion of this product?
This thing can sum a stereo signal, pad your gain, reverse your polarity and lift your ground while being dead quiet because it's passive. Plus it uses a real Jensen transformer and it's built like a tank! It's only a little bigger than a typical DI so it won't take up all the space in your gig bag or guitar case. This thing will probably last forever!
Héctor Varela, Submitted: 1/21/2017
Product Rating
Amazing direct JDI box
What is your opinion of this product?
Super clear sound. I'm very happy working with it.
AMS Responds:
Chris McGowan from Chicago Submitted: 1/30/2012

Great DI, perfect for Studio and Live!
BOBBY from Thousand Oaks, California Submitted: 3/26/2011

BJ Knights from Franklin, MA Submitted: 8/12/2010

Great Tone! Excellent DI...
Byron from USA Submitted: 2/5/2008

What a DI should be
Your general opinion of this product.

It's very sturdy and "road-worthy". The jacks and switches are protected by the outer steel cover.

It has the usual DI switches plus a merge feature that sums two inputs into one output.


This unit isn't the cheapest but it's worth the price, considering the sound quality.

The sound is transparent, clean and quiet. The best sounding DI is the one you can't hear (what you put in, you get out). The Jensen transformer is very warm and natural sounding. Radial's ProDI also sounds very good for less money.

rock, fusion

guitar and keyboard player, sound engineer

The bottom line is this: If you want a high-quality, great sounding DI, you can't go wrong with Radial. I can honestly say that, in 20 years of music production, this is the best DI I have used and would recom
Radial JDI Passive Direct Box Smart Sheet
SmartSheets are downloadable, printable quick information sheets in pdf format designed to clearly highlight the benefits and features of each Radial product.

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