Radial Engineering JDI MK3 Passive Direct Box

by Radial Engineering

Product Features

• 100% passive design - no phantom powerJensen transformer equippedDual function inputs w/2 channel mergePolarity reverse switchSpeaker level input circuitUltra-durable welded steel chassisDouble sided printed circuit boardProtective channel for switchesGround Lift and Pad switchesNo-slip bottom pad

Product Details

• Shipping Weight: 1.9 pounds (View shipping rates and policies)
• ASIN: B0002GIRAC
• Item model number: R800 1010 00
• Average Customer Review: 5.0 out of 5 stars  See all reviews (1 customer review)
• Amazon Best Sellers Rank: #13,341 in Musical Instruments (See Top 100 in Musical Instruments)
  • #22 in Musical Instruments > Recording Equipment > Signal Processors > Direct Boxes

Product Description

The worlds finest passive direct box! It employs the legendary Jensen® JT-DBE transformer which is renowned for its warm Bessel response curve. Virtually zero phase distortion, exceptional signal handling and the advantage of true isolation to eliminate hum makes the Radial JDI the choice for live sound reinforcement. ?  Jensen Transformer equipped passive DI ?  100% isolation eliminates ground loops ?  Virtually zero phase & harmonic distortion ?  Exceptional signal handling ?  High common mode noise rejection The Radial JDI 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 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. The JDI may be rack-mounted using the J-Rak and is also available in a stereo (2-channel) version called the JDI Duplex and the 6-channel rack-mountable JD6.  

Customer Reviews

Most Helpful Customer Reviews

3 of 3 people found the following review helpful:

5.0 out of 5 stars Terrific Passive DI, February 16, 2011

By 

DeusEx (OH) - See all my reviews

Amazon Verified Purchase

This review is from: Radial Engineering JDI MK3 Passive Direct Box (Electronics)

The other reviewer gave excellent specifics about the tone and feel with vintage instruments and amps. This is what this box was designed for and where it will really shine. My application is a little different. I wanted a quality "passive DI" for multimedia and for the occasionaly electric-accoustic guitar input.

What is a DI (AKA a Direct Box)?
A DI is basically a device that in the most basic sense electrically isolates and transforms unbalanced line level signals (signals from most stage instruments and most consumer electronics) to balanced line level (on both powered and unpowered lines) singnals commonly found on PAs and stage mixers used for mics. There are two categories...Passive and Active. Passive DIs do not require any addition power source like batteries or AC input. They are simply a transformer that transformed the input signal to an output signal. I will skip the physics of it though. Active DIs are a little more complex and generally cost more. Sound quality on cheaper models is horrible. These DO require additional power such as batteries or "Phantom Power" on the higher end units. Without getting too deep into the physics here, these depend on the unit's "rail voltage" to prevent clipping. The more dynamic the insturment and performance, the more rail voltage you'll need. As I said though, this is passive DI so it's produces a nice subtle sound curve even as it reaches satuaration (passive DI speak for overdrive.)

Why do you need a DI?
Whether your using an insturment or a multimedia device like a DVD, iPod, or laptop...these will almost always be unblanced line level outputs either thru 1/4" jack, 1/8" jack, or RCA jacks. Just using a cable adaptor to mate these with the common 3-pin XLR for balanced line level signals found on PAs and mixers will at the very least create tons of unwanted buzz or hum. And at the worst (and acutally very likely) short out your device. Many PAs use Phantom Powered mic lines and these will instantly overpower any device mensioned above. Instead you need something to transform and isolate the two halfs of the system. This devices transformer and circutry does just that.

The details. First off, I pleased to say that this unit is the newer model JDI. This is not the mk3, but the next gen. I'm very happy about that dispite the description. Inside this box is a genuine Jenson audio transformer, reguarded for their superior sound quality especially with vintage equipment. On the input side you get a 1/4" in and 1/4" thru for passing to a stage amp. Or you can use "merge" button and combine the two jacks to convert a L and R stereo signal to mono. Nice for multimedia and keyboards. I'm using a Hosa 3.5mm TRS to Dual 1/4 in TS (1/8" stereo jack to dual mono 1/4" jacks) for my application. On the input side is a "pad switch" to soften sounds like MP3 and CD players. On the Output side is a single balanced XLR output (1 channel mono), a 180 degree "flip switch" for reversing polarity to work with foreign made sound equipment. It has a ground lift switch to isolate grounds and get rid or noise due to ground loops. The device is built to isolate grounds automatically, but if you still have noise you suspect due to grounds, try this. Lastly is a speaker parallel button that I'm not entirely sure what it's used for. it's small in size, about 4"x6"x1.5" and roughly 2 lbs. It's made of a solid steel case to protect it from damage on stage while at the same time create an "EM cage" to shield the internal electronics from outside interference.

All in all it's a great box with excellent sound quality. It's far more than I need, but I hope to grow into it. For users that don't want to spend an arm and a leg Radial does make really great DIs that aren't as expensive. For AV/multimedia users there's the ProAV1 which is purpose built as a swiss army knife solution for hooking your audio out to any PA or stage mixer. For instrument users there's as many DIs as stars in the sky to fit any budget.