Radial JDI MK3 Passive Direct Box

Get top-notch DI sound without batteries! The JDI boasts a Jensen isolation transformer, polarity switch, ground lift and a -15 dB pad in a rugged steel box.

The Radial JDI MK3 passive direct box is a dynamic and versatile DI box that keeps your signal as clean as can be with its rugged chassis and smart passive circuitry design. A merge switch allows for the 1/4" input and 1/4" through output to be switched over to stereo inputs for keyboards or other stereo sources, and an XLR out sends your signal to the venue's PA system. This industry-favorite DI box is also equipped with a -15 dB pad switch, a reverse polarity switch, a speaker pad switch, and a ground lift switch. Your MK3's JDI transformer is housed inside a nickel container to keep out electromagnetic interference, so your signal remains clean and pristine throughout your performance.

The Power of a Passive System

The really cool thing about a passive system like the one in your Radial JDI MK3, is that there's no physical contact between the input and output signals. The signal is transferred across the core material via an electromagnetic field. That takes care of buzzing problems associated with ground loops -- and there's a ground lift switch on the side of this baby if unwelcomed noises still persist.

Versatile for Many Instruments -- Use it in Mono or Stereo

You can use your JDI MK3 for a whole bunch of different instruments -- bass, viola, guitar, keyboards...you name it. When you plug into the 1/4" instrument input, the JDI will split your signal to a 1/4" thru-output and an XLR output, so you can send one signal to your amp and the other signal to the venue's read more PA system. If you engage your DI box's merge switch, the "thru" jack becomes a second input for stereo sources such as keyboards.

JDI Transformer for Vintage-Sounding Breakup

In the world of audio recording, there are few sounds worse than digital clipping. You'll never have to worry about that with this Radial direct box, because of its awesome JDI transformer. If your signal gets too hot, it saturates rather than clips, which tends to give off a cool vintage-sounding distortion. This transformer is housed inside a nickel cylinder that keeps your signal protected from electrical interference from other gear on stage.

Built to Last

This baby is hard to break. Its steel chassis will take the abuse dished out on the road without any serious problems. Your inputs and switches reside in slightly indented panels that are hard to bang and ding, even if you drop you DI box by accident. Also, a non-slip pad on the bottom keeps your DI box from slipping, while insulating it from electrical contact through the floor. It's built to kick around in your gig bag for years to come.

All the Switches and Controls You Need

On each side of your JDI MK3 are a set of switches. Your -15 dB pad allows this baby to take in hotter signals, and the merge switch next to it allows you to utilize your 1/4" input and 1/4" thru jack as stereo inputs. The reverse polarity switch on the other side can help reduce feedback if you're using acoustic electric instruments, and the ground lift switch takes care of any remaining unwanted buzz or hum that might sneak in. The speaker switch on the right introduces a bandpass filter to give your tone a speaker cab sound, adding a little character to your output.

With all these features and top-notch sound, it's no wonder Radial calls this little guy the "world's finest passive direct box"!


- Single-channel passive DI box
- Passive design prevents ground loops
- One 1/4" input
- One XLR output, one 1/4"/TS output
- JDI transformer housed inside nickel casing
- Can handle high input signals without distorting
- 15 dB pad switch
- Merge switch for stereo input connectivity
- Reverse, ground lift, and speaker pad switches
- "Book-end" design protects switches and connectors
- Rugged steel outer chassis keeps inner circuitry and your signal protected
- Non-slip pad keeps pedal from sliding around on smooth surfaces
- 2.2 pounds
WARNING: Cancer and Reproductive Harm - www.p65Warnings.ca.gov.
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- Audio circuit type: Passive, transformer based
- Number of channels: Single channel (mono)
- Frequency response: 20Hz ~ 20KHz (+/- 0.2dB)
- Dynamic range: 135dB
- Maximum input: +21dB @ 20Hz ~ 20kHz
- Total harmonic distortion: 0.05% from 20Hz ~ 20kHz @-10dB
- Phase deviation: 0.3* @ 100Hz; 3* @ 20Hz
- Input impedance: 140k Ohms, unbalanced
- Output impedance: 150 Ohms, balanced

- Transformer: Jensen JT-DBE, 12:1 ratio
- Shield: Dual Faraday, mu-metal can
- Input pad: -15dB
- Merge: Sums left & right sources to mono
- 180* polarity reverse: Inverts absolute phase
- Ground lift: Disconnects pin-1 at XLR output
- XLR configuration: AES standard (pin-2 hot)
- Speaker filter: -30dB pad and band-pass filter
- Connectors:1/4" in & thru, XLR-M out

- Construction: 14 gauge steel chassis & outer shell
- Finish: Baked enamel
- Size: (W x H x D) 84 x 127 x 48mm (3.3" x 5.0" x 2")
- Weight: 0.70 kg (1.55 lbs)
- Shipping Size: W x H x D: 102 x 76 x 165mm (4" x 3" x 6.5")
- Shipping Weight: .87 kg (1.92 lbs)
- Power: Passive, no power required
- Warranty: Radial 3-year, transferable
Dimensions and Weight in Packaging
Base Item
Shipping Weight: 1.73 lbs
Shipping Dimensions: 6 x 4 x 3 in
Manufacturer Part Number (MPN): R800 1010
Warehouse Resealed
Shipping Weight: 1.73 lbs
Shipping Dimensions: 6 x 4 x 3 in
Manufacturer Part Number (MPN): R800 1010

For support or warranty questions, please contact the manufacturer:
Phone: 604-942-1001

Radial JDI mk3 Passive Direct Box

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 1/4" 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 mu-metal 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.


- Jensen Transformer equipped passive DI
- Eliminates hum and buzz from ground loops
- Virtually zero phase & harmonic distortion
- Exceptional signal handling and noise rejection

Reviewers gave this product an overall rating of 5 out of 5 stars. (25 ratings)
Submitted March 24, 2008 by a customer from gmail.com

"Stop searching... your DI troubles are solved."

Overall: 5 out of 5 stars
(see rating details)
The search is over.
I used this on my 6 string bass... WOW! I was having a bit of a hate on for the bass as I felt it was a bit lack luster going through my other passive DI box. This was different... no lie my B string sounded tighter, and the pups on the bass sounded clearer. I will not let this DI box go - EVER!
There's a number of cool things it can do... but I'm just DI'ing it no need yet for the other bits...
Ease of Use
plug-n-play not pray
TANKS should be built this well...
I'd pay more but I'm glad I didn't have to.
Manufacturer Support
They're Canadian... so polite.
The Wow Factor
I want the JDI rack for my synths now

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