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
This 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'
The JDV Mk3 'Super DI'.
Today's JDV Mk5 'Super DI'
Today's JDV Mk5 'Super DI'.

JDV Mk5™ Development

The origins of the JDV can be traced back to the 1980's where Vancouver was a hot-spot for some of the most commercially successful recordings of all time including works by artists Bryan Adams, AC/DC, Metallica, Elton John, Aerosmith, Loverboy and Bon Jovi. Home to Bruce Fairbairn and Bob Rock, Little Mountain Studios was the epicenter.

Behind the scenes, was studio designer and technical whiz John Vrtacic. John was the guy that designed monitors, modified and rebuilt the consoles and created many of the unique tools that set Little Mountain Studios apart. Artists would often talk about the amazing bass sound that John's custom-made direct box produced. John had discovered a way to buffer the signal without the use of negative feedback and when scoped, his DI produced an incredibly accurate sonic picture that was simply unattainable by any other.

Soon after Radial launched the Radial JDI passive direct box, we asked John's assistant Ron 'Obvious' Vermulen to compare various direct boxes using his Audio Precision tester to prove that the JDI was best. During these tests, unbeknown to us, Ron also tested John's custom made direct box. This is how we discovered that John's box was so much better than the other active DIs on the market. We approached John to see if he would sell us the design. He did and the first generation JDV – V for Vrtacic – was born.

Updating the feature set

Over the years, the JDV has gone through several changes. During each evolution, improvements have been made to enhance the performance while remaining true to John's original design.

Connectivity and level controls

Although the previous JDV had two inputs, you had to manually select between them using a side panel switch. We felt that it would be advantageous if the artist could select the instrument by also using a remote footswitch. Being able to adjust the level between the two instruments also enables the artist to switch between an active bass and a passive one without having to readjust the levels on the bass amp or mixer channel.

Impedance matching

Today, source instruments can range from simple magnetic pickups, to piezos, active sources or even microphones. To our mind, the JDV had to do it all. Magnetic pickups tend to sound warm and natural when they see a 200k-ohm load. Yet piezos need to see a 10 meg-ohm load in order for them to sound full and natural. The JDV has it all including Radial's unique Drag™ control load correction that lets you adjust the load to suit a particular pickup and playing style.

Adding a microphone

There is no question; a well positioned microphone in a proper acoustic environment will produce the most natural sound of all. The problem however is that when used live, mics can pose a number of challenges including positioning, feedback and of course the less than ideal sound that is produced when excessive EQ'ing is applied. Combining the sound of a piezo with a microphone helps tremendously as the pickup can produce a greater output. The real magic however comes when you phase-align the two sources. To this end, we added a mic input, 48V phantom, and a Radial Phazer.

Filters and control

One of the most amazing tools you can use on stage (and in the studio!) is a high-pass filter. This simple control eliminates low frequency resonance that can cause an instrument to get muddy and cause weird feedback on stage. With two HPFs, the new JDV allows you to dial-in the size of the instrument so that your upright, acoustic guitar, viola, mandolin or fiddle will properly sit in the mix without getting lost.

Remote controllability

The optional JR-2 actually does more than simply select input channels. It can also be used to mute the output going to the PA or stage amp while leaving the dedicated tuner output on at all times. This of course enables quiet on-stage tuning while eliminating the confusion and panic that can occur when the artist decides to change instruments mid-way through a song due to a broken string. Muting the instrument means that the monitor and FOH engineers do not need to turn down the acoustic channel – the artist can merely mute it as needed.

Recording Direct

With more and more recording and tracking being done in the comfort of private studios, session players are often called to these remote locations where they will record direct for further Reamping after the track has been laid down. A special signal level booster may be activated that increases the output from a typical DI out by 20dB to enable direct line level recording. This assures your bass track will be recorded with maximum fidelity no matter what the equipment setup.

Rack mounting

More than ever, stage managers are insisting on having backups on stage to content with any and all eventualities. When 20,000 fans are in the audience, there is no time for system breakdown. And even though Radial is well known for having the least service problems in the industry, having a backup is the best insurance you can ever have! The new JDV can be rack mounted individually or two may be mounted side by side for the most demanding tours.

Global power supply

Global touring a reality, power supply issues have now become a significant concern. The new JDV employs an external switching supply with a locking XLR that is able to handle any input voltage from 100V to 240V. One merely changes the IEC cable to suit.

History – A Tribute to John Vrtacic

The originally Radial JDV was developed by John Vrtacic in the 1980's 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 Jovi, 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,
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 Swedien, Bill Fertig 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.