Although passive direct boxes have been around for years, the liberal use of inexpensive, low quality transformers have the not so obvious consequence of compromising the sound. This is caused by the use of low-permeability steel in the transformer core which has the adverse effect of causing group-delay (phase distortion) and a lower saturation point (harmonic distortion), which of course are most prevalent at lower frequencies.

With the advent of better sound systems and recording techniques, the demand for quality grew. This spawned the development of active direct boxes as a means to improve the performance of these lesser passive DI’s without adding cost. The active DI herald in a new generation of improved sonic performance but alas, did so at the expense of isolation.

Enter the Radial JDI

The Radial JDI was introduced in 1996 as means to offer the advantages of isolation while raising the bar in sonic performance. The use of a high quality Jensen® DBE Transformer is critical and is easily justified when one considers the hundreds of thousands of dollars spent on the other components of an audio system in the quest of great sound.

The first version of the JDI was a simple device that was made using an extruded aluminum shell and an inner ‘drawer’ or frame that contained the PC board and electronics. A dual recessed control panel was developed to protect the more fragile toggle switches. The original version was soon updated with the introduction of the stereo to mono ‘merge’ function in
1997. This handy feature was met with the approval of audio engineers everywhere and has since become a staple of the Radial direct box feature set.

In 2001, the JDI was given a major face-lift and redesigned using our innovative and extremely durable book-end enclosure system, which is used throughout the Radial product line. The book-end design provided a number of major advantages: The I-beam construction increased the inner frame strength thus reducing potential for outside stress; we were able to employ higher duty cycle 'push' switches instead of the more fragile 'toggle' switches; build time was greatly reduced allowing us to keep our manufacturing local thus ensuring the highest possible control over quality; we could also pass the reduced manufacturing costs on to the end user, offering the best performance in the industry at reasonable prices.

 
JDI Frequency Response Graph - an amazing 20Hz - 20 kHz +/- 0.2 dB

"Fast forward 12 years later… Radial Engineering Ltd… (formerly CableTek ltd.) became the Canadian distributor for Jensen. We were supplying parts such as cable and connectors for sound companies to build snakes. But the market began to change. The new wave of more affordable technology forced an economic change. Sound companies were doing less-and-less on-site upgrades or custom manufacturing and keeping a full-time tech on staff no longer made sense. Our customers started asking us to build solutions. Next thing you know, we began building snake systems using Jensen transformers to fill the need. And in 1996, the first Radial JDI was born."

The process is simple: If you intend on building a better mousetrap, you have to stat by understanding what makes it work and where things can be improved. This has been the foundation of every piece of Radial gear we have ever developed.

When we assessed the various passive DI boxes that were commonly being sold, we noticed several pitfalls. First and foremost, most of them sounded terrible! It turned out that the quality of the transformer was the culprit. Good transformers such as a Jensen are expensive to build. They incorporate very specific manufacturing processes that are not easily matched. For instance, the inner core that creates the magnetic bridge between the primary and secondary windings is critical to the transformer's performance. Jensen hand stacks the various nickel and steel laminations in such a way that the signal is transferred without compromise. Then, to ensure each transformer is made within very tight tolerances, they are wound on Swiss-made digital winders. These not only ensure the exact wind count is maintained, but these machines spread the ultra-fine windings in a proprietary fashion to achieve the sonic results. The transformer is then housed inside a mu-metal can where the magnetic bridge is protected from outside fields. Keep in mind that DI boxes are often placed right on top of bass amplifiers and they have huge noise-emitting power transformers that if left unchecked, will cause the unprotected transformer to distort. For a passive DI box to work well, it must have a very high input impedance and then must deliver the sound without noise or artifact. This is part of why Jensen has become the world's most coveted audio transformer. And rest assured, the sonic results are impressive!

Next, we looked at form and function and had to face up to reality: DI boxes get no respect. They are tossed around like an old shoe, kicked on the stage and then expected to work 365 shows a year. We noticed that the switches and connectors were often exposed to the brutalities of the real world. We also noticed that it was common to find plastics being used as part of the mechanics. It just did not seem to make sense.

The first version of the Radial JDI was built using an aluminum tube and a slide-in chassis. The concept worked well! The design created a protective zone around the switches and connectors at each end. But the trouble with the design was that it took a lot of time to build. The aluminum channel had to be cut and then sanded by hand to eliminate burring. And because the connectors were all hand soldered to wire leads, it took forever to produce.

In 2002, we redesigned the JDI with a totally new concept in mind. We had found that many sound companies needed a rack-mountable solution for certain tours. What if we could create a new platform that would allow several JDI's to be rack-mounted when needed? This is how the new 'bookend' concept came to light. The bookend would provide the protective zone, while the inner I-beam construction would provide the added rigidity. And because you could rack mount eight of them in two spaces, it solved yet another big problem. We have never looked back.

Some of the early JDI adopters included Bruce Springsteen, Celine Dion and Brian Adams. In fact it was Bruce's wife that told bass player extraordinaire Mark Egan about it and Mark purchased on from us at our very first NAMM show. The Radial JDI is available in several formats including stereo with the Duplex and in a 6-channel rack version called the JD6. Folks that use the Radial JDI include: Tony Levin, best known for his amazing bass work with Peter Gabriel; the David Letterman Show; the Grand Ole Opry; and mega band U2.

Thanks to these early adopters and all of the engineers and musicians that actually took the time to listen to the difference, the Radial JDI has gained a tremendous following and has become the standard passive DI in use today.