even harmonics
The graph shows a text book example of perfect even order cascade. Notice the five harmonics, each decreasing in amplitude as it rises.
odd harmonics
Graph shows a problematic succession of
even, then odd order harmonics. This will
likely result in a harsher and more brittle tone.
tone robbing negative feedback
Non-inverting operational amplifier (op-amp)
with negative feedback.
Pickup to amp circuit.
Album Covers
You’ve been hearing the JDV for years! The original JDV was a staple at Little Mountain Studios and used on these highly successful albums.
The Original JDV Mk1
The original JDV Mk1, circa 1998
Today's JDV Mk3 'Super DI'
Today's JDV Mk3 'Super DI'.

JDV Development

If you were to imagine the perfect direct box, what would it be? Would it change the sound of your instrument or would it retain the natural character? For the purest, changing the sound of a 1962 Jazz Bass makes no sense. If that particular bass does not sound right for a given track, do you EQ the heck out of it or do you simply go fetch the active 5 string bass?

The Radial JDV is all about retaining the signal purity. At least until the track is recorded or sent to the PA system. From there, feel free to tailor the sound as you see fit. Our point is simple: We believe a direct box should be as faithful to the instrument as possible.

Distortion, the Good, Bad and Ugly!

There are many types of distortion. Humans are particularly fond of even order harmonic distortion where descending harmonics cascade evenly to create what is known as a warm Bessel curve. This is the good distortion that often typifies the very finest vintage gear. Unlike today's highly efficient class-AB circuits that separate the signal into positive negative parts, amplify, rectify and somehow manage to magically bring all of the frequencies back together in perfect sync… the JDV is old school. It is pure class-A and employs full size, discrete parts. This means it does not suffer from zero-cross distortion which in variably exaggerates inter-modulation and phase distortion.

Our ears are even more sensitive to harmonic distortion. This is the fuzz like effect that occurs when the instrument signal overloads the circuit, causing it to clip or square wave. The greater the internal rail voltage, the more headroom. A typical DI box will have 3 volt rails. A good quality mixer will have 16 volt rails and a world class console will have 24 volts rails. The JDV's 32 volt power supply delivers 30 volt rails for unmatched signal handling. In fact the JDV has so much headroom; the pad is actually on the output so that it will not overload your mixer! More headroom equals less distortion.

If you painstakingly invest the time to reduce all types of distortion, something funny happens… things start to sound better.

Negative Feedback Loops

Audio pioneer Rupert Neve spent most of his life looking for ways to eliminate negative feedback loops in audio circuits. This makes sense. If you look at a basic amplifier circuit design, there is always a positive and negative input. The positive is used to amplify the signal while the negative is used to stabilize the amplifier from run-away. A resistor controls the amount of negative feedback that is allowed in the circuit. As soon as you mix the negative with the positive, some signal will be phase cancelled. John Virtacic discovered a way to control the amplifier without using negative feedback, a process that has eluded all others and sets the JDV completely apart.

Low distortion, exceptional headroom and a circuit completely void of negative feedback. You are beginning to understand why the JDV is so much better.

Adaptable to Any Instrument

The JDV is a unity gain device. In other words, it is designed to capture the sound of the instrument and send it along its way without introducing coloration, artefact or distortion. But even the finest audio circuits will impart some character. The variables include the type of pickup being used, the type of circuit in the buffer and the impedance that interfaces the two. To capture the sound of a vibrating string, one usually captures the vibration via a magnetic coil known as a pickup or by capturing the vibration of the body using a pressure sensing piezo electric element. Both work differently.

Magnetic Pickups

The magnetic pickup is very similar to a transformer. It is passive. When the transformer is connected to an amplifier, a circuit is created. A pickup will react differently depending on if it is a tube amp or solid state amp. Most manufacturers employ a 1 meg-ohm input on their equipment. This 'standard' set by Leo Fender in the 1950s for tube amps remains and works perfectly well with electric guitars. But when a guitar is connected to a solid state input, the tone is never quite right. We discovered this when developing the Radial JD7 guitar splitter. As soon as you put a buffer in between the instrument and the amp, the sound changes. We came up with a solution called Drag Control that enables the musician to dial in the correct load so that the pickup sounds and feels as if connected directly to the amp. The JDV's Drag control let's you adjust the load on your pickup from 10kOhm to 1 megOhm so that it sounds right.

Piezo Transducers

If you have ever connected a piezo pickup to an instrument, you have probably been disappointed. Piezo pickups tend to squawk and sound very peaky. This is because they work best when presented with a very high input impedance in the 4 to 10 meg-Ohm range - in fact, the higher the better. But with a higher input impedance comes a problem: noise. High impedance circuits are much more susceptible to noise than low impedance circuits. To avoid the problem, circuit designers reduce the impedance and noise goes away. The trade off is second rate tone. The JDV solves the problem.

Switch the Drag Control off and the JDV's input impedance jumps way up to 4megOhms: four times higher than the others. This is achieved by carefully selecting parts, trial & error positioning on the PC board and locating the power supply out of the protective metal shellthus the external brick. The results are immediately audible: smoother tone, less peaky, less feedback on stage and a more natural tone.

Unlimited Connections

PA systems have advanced tremendously. When the first direct boxes appeared, the bass signal travelled from the instrument's pickup to the stage amp and was split to the PA where the signal was split again to front of house and wedge monitors. The lowly pickup had to drive all of these inputs leaving the bass player with a tone that was lacking. Active DIs helped tremendously. They buffered the signal, pushing it along the way.

Today, in-ear monitors have elevated the demands whereby musicians now expect great sound each and every night. In the studio, countless repetition with hours of punch-ins has now been replaced with sophisticated software that can fix bum notes and Reamping now allows the engineer to work on the sound well after the track has been recorded and the musician has been sent home.

When developing the JDV feature set, we considered both. In other words, we introduced a series of connectivity options that would allow the musician to travel between the studio and live stage without hindrance. Two inputs would allow the session player to switch between a vintage Fender P-Bass or a 5 string active bass with a simple push of a switch. Four hi-Z outputs would enable the musician to connect to a stage amp, guitar tuner, Pod or second amp if desired. In the studio, the JDV's low-Z out could be used to record a dry track and then Reamped through the JDV if so desired. One could then drive as may as four amps at the same time!

The JDV delivers unmatched signal clarity without hype, is able to handle the widest range of instruments and is equipped all the connectivity needed for live stage or studio. We think you will be blown away.

History – A Tribute to John Vrtacic

The originally Radial JDV was developed by John Vrtacic in the 1980s who at the time was the Chief Technical Engineer for Little Mountain Studios in Vancouver, British Columbia. Little Mountain was 'home' to producers Bruce Fairburn and Bob Rock and their astonishing number of hit records from artists like Aerosmith, Bryan Adams, AC/DC, The Cult, Metallica, Bon Jovie, Loverboy and so many others. Little Mountain's huge 'bass sound' became legendary and is stamped forever on millions of albums sold worldwide.

Photo of John Vrtacic
John Vrtacic,
www.vrtacicdesign.com
March 27, 1948 – August 19, 2009

In 1997, Ron 'Obvious' Vermulin, Chief Technical Engineer at Bryan Adam's Warehouse Studios (Ron also designed the Mutt Lang/Shania Twain studio) was asked to test the 1st generation Radial JDI passive direct boxes against a number of 'popular' DIs and it was from these tests that the Radial Green Report was produced. While testing the Radial JDI, Ron decided to run the same tests through one of the original John Vrtacic's custom-made direct boxes. Although the Radial JDI faired better than all other commercial units, the custom-made JDV was clearly the best. Ron suggested we contact John and build a commercially viable version of the JDV.

Radial purchased the circuit design from John and hired him as a consultant during the development stage. The first generation JDV employed a rechargeable battery pack as part of the power supply circuit along with an external supply. Because the JDV employs a class-A circuit, 48V phantom is unable to provide sufficient current to supply the circuit. The belief was that the rechargeable battery pack could sustain the power-hungry design while using phantom power to trickle charge the battery when in use. This would also eliminate the need to plug in the JDV. Although the system worked reasonably well, having to pre-charge the batteries before use was clearly a painful compromise. In 2001, the decision was made to update and redesign the JDV.

The newly designed JDV is outfitted with a more powerful external brick that is able to deliver a consistent supply to the unit. This of course requires power, but since most stages today have power distribution readily at hand, plugging in is no longer a concern. A series of extra functions were also added including Drag Control, filters, and a whole bunch of connectivity.

Over the years, the Radial JDV has gained a strong following. It started when influential artists like Tony Levin, Will Lee and Alain Caron began using it on their bass tracks and became firmly cemented in the industry after it won a number of comparative tests in influential magazines such as Mix, Recording and Bass Player. And with many of the world's top engineers like Bruce Sweedien, Bil Vortig and Butch Walker along with musicians the like of Marcus Miller, Joe Satriani and Victor Wooten, the JDV continues to spawn new fans everywhere.

The Radial JDV is dedicated to John Vrtacic – (John direct Vrtacic) a friend and a tremendous supporter that will always be remembered at Radial.