Radial Engineering > Radial Engineering JDV MK3

Radial Engineering JDV MK3

Our flagship direct box. Features a highly acclaimed Class-A feed-forward circuit design with huge 30V internal rail voltage for absolute no-compromise performance. The JDV Mk3 expands the functionality of regular direct boxes by providing a zoned working environment with 4 instrument outputs, in addition to the traditional balanced out. This allows unprecedented flexibility and creative setups.

Radial JDVmk3 Super DI

  • Class-A feed forward design
  • Huge 30-Volt internal rail voltage
  • Innovative Drag control
  • Variable impedance to 3.9 Meg-Ohms
  • Unique zoned design concept
The Radial JDV Mk3 is arguably the most advanced and sonically superior direct box made today. With 100% class-A circuit and a 30-Volt internal rail voltage, the JDV combines exceptional sonic quality and unmatched dynamic handling for the most natural and uncolored sound possible.
Designed as a creative tool, the JDV introduces a concept of ‘Zones’ with choice of two inputs, four instrument amplifier outputs, and a unity-gain transformerless output.
Features include Drag control for precise pickup load correction, 3.9 meg-ohm input impedance for piezo pickups, hi-pass and lo-pass filters, full LED status indicators, polarity reverse and all of the other features one would expect from a Radial DI.
The Radial JDV Mk3 is designed for use in both the studio and live performance and is suitable for all instruments where added reach is required and retaining the original sound of the instrument without distortion or coloration is paramount.
JDV Features & Functions
The purpose of the Radial JDV is to provide the user with the very best interface between the instrument and the recording or sound reinforcement system. Today, the 'instrument' is not just the guitar, bass, or contrabass, but the instrument in combination with the amplifier, effect rack and pedals.
In order to effectively capture the complete sound, the very fabric of the direct box was revisited. The artist, whether guitarist or bassist, will usually have more than one instrument and a variety of outboard effects and amplifiers that make up his or her sound. This is his environment, her comfort zone, their creative world. The engineer and producer may want to record this sound by traditionally mic’ing the amplifiers, but with today’s advanced editing equipment and re-amping tools like the Radial JD7 or Radial X-amp, simultaneously recording the clean unaltered source is now an essential part of the recording process. Thus the concept of zones was developed: An input zone for the instrument, the musician’s zone for his creative environment, and an output zone for the engineer.
The JDV is actually designed to be a creative tool. By providing an array of connecting options, the intent is to open the door to new sounds and spur on the creative process of making music. Now isn’t that what a good interface should be?

Instrument Input Zone

  • LED Status indicators include system on, signal present and peak level overload.
  • 80Hz high-pass filter reduces excessive bass for more clarity. Elliminates run-away resonant feedback from acoustics!  
  • 7kHz low-pass filter gently rolls off high end edge and reduces noise and hiss from older instruments. Very musical!
  • Vary-Z switch selects between ultra-high 3.9 Meg-Ohm input impedance and Drag control for load correction.
  • Drag Control is used to retain the natural feel of the instrument on the active auxiliary outputs by correcting the load.
  • A or B input switch selects between the two instruments inputs for fast changes.

The Radial JDV begins with an input selector for choice between two instruments. Often, when recording, the simple act of picking up another instrument will cause the musician to play a passage differently and often, this change can lead to magical results. In concert, being able to pick-up a spare or alternately tuned instrument without having to reconnect is a joy.
On the left, three LED indicators provide power-on, signal present and overload status. Two on-board filters are provided. A low-cut filter (high-pass filter) is used to reduce rumble and run-away resonant feedback from acoustic instruments. For bass, this will tighten up the bottom end without losing the fundamental. A high frequency roll-off (low-pass filter) gently rolls off noise from older equipment and helps tame overly brittle instruments.
The JDV Mk3 includes a special feature we developed called Drag Control™. This function was originally developed on the Radial JD7 Injector as a means to re-introduce the loading that is lost when the guitar pick-up no longer is coupled directly to the amplifier. Laboratory engineers have perpetuated a ‘myth’ that ‘loading the pick-up’ is a bad thing when in fact, correcting the load is critical to achieving musical results. Without proper impedance matching, the sound can become brittle and harsh. This of course is most noticeable when recording.
The JDV offers a choice of a 3.9 Meg-ohm input impedance (the highest in the industry) to properly match piezo pickups and variable loading we call Drag Control™ that combines resistance and impedance with a single dial for effective load correction.

Engineer's Output Zone

  • Unique book-end design creates a protective boundary around the switches and connectors.
  • Strain releif for power supply cable.
  • XLR balanced mic level output can drive runs of up to 1000 feet without appreciable noise.
  • Polarity reverse switch flips the polarity from the AES standard Pin-2 to Pin-3 on the XLR and is used when combining sounds that may be out of phase.
  • -15dB pad: The JDV rail voltage is so huge, we put a -15dB pad at the output so that it will not overload your mixer.
  • Ground-lift disconnects the ground path at the XLR output. This would be used when a ground connection is made at the input side such as with a keyboard.
  • 42V external DC power supply with cable lock to assure the JDV will not accidentally lose its power connection.

The output panel is the engineer’s zone. The XLR output provides a clean, unaffected signal to the console for future processing or doubling with the mic’ed performance. Because of the JDV’s huge internal rail voltage and exceptional dynamic handling, an output pad is provided so that it will not overload the console or pre-amp. A polarity reverse switches the XLR output from AES standard pin-2 hot to pin-3 to adapt to vintage equipment while providing another creative tool to broaden the audio landscape.
The most important feature of the Radial JDV is the sound quality. At Radial, we pride ourselves in the fact that our direct boxes do not change the original sound or impose a particular EQ curve to an instrument. We do not believe it is our place to alter the sound of pre-CBS Fender or a PAF equipped Gibson. Our task is to provide the original sound of the instrument without adding color, distortion or hype. We call our sound the Un-Sound™.
To achieve this level of audio purity, every aspect of the Radial JDV’s circuit must be optimized for minimal distortion. And unlike other manufacturers, we do no just examine harmonic distortion, but zealously try to eliminate zero-cross distortion, phase distortion, inter-modulation distortion, linear response distortion, square wave distortion and headroom. By treating each of these carefully, the result is predictable: you get great sound.
The Radial JDV employs a unique Class-A feed-forward circuit design and a newly developed high-voltage, low-noise power supply. Class-A circuits although less efficient, do not suffer from zero-cross distortion. This is why Class-A circuits are ‘the choice’ for audiophiles. The JDV’s unique feed-forward design means that we have eliminated the traditional stabilizing feedback loop that is in the ‘easy circuit designer’s handbook’. This unique ‘high-wire without a net’ circuit design is amazingly adept at handling square ‘pulse’ waves without ringing or overshoot. Put the JDV up on a scope and one will see a sharp, 90 degree rendering that is unequaled in the business.
The exceptional internal 30-Volt rail voltage is of particular importance at bass frequencies. In PA systems, bass drivers are commonly driven with as much as ten times more power than the high-frequency drivers. This is because bass, with its longer wavelengths, requires significantly more power to generate. This is the same at the circuit level and is critical to achieving a tight, natural sound. Look inside the JDV and you will see huge current storage capacitors that are the size found in small power amplifiers. By providing ample impulse energy storage, dynamics are maximized thus fulfilling the capacity of today’s most advanced recording devices. The benefit of having upwards to 10 times more headroom than a traditional DI means that the JDV never chokes even with the most powerful active bass or extreme digital sample.

JDV Construction

  • I-beam construction eliminates external stresses on PC board.
  • 42-Volt power supply input jack.
  • Cable lock strain relief prevents power loss from accidental unplugging.
  • Large, oversized capacitors for maximum headroom.
  • 100% Class-A discreet circuitry (no op-amps!).
  • Baked enamel finish for added durability.
Like all Radial products, the JDV is built to last. A unique book-end design provides easy access to switches, knobs and jacks while providing a protective barrier against abuse. Inside, the JDV employs a folded I-beam construction that makes impossible to torque the PC board. This eliminates stress on the solder joints and pretty much eliminates servicing problems. The distinctive dark-blue baked enamel finish resists scratching while also making the JDV relatively invisible under cameras and stage lights. Finally, a full-bottom no-slip rubberized pad provides both shock mounting and staying power to keep the JDV in one place.
The JDV employs an external power supply as 48V phantom power is unable to provide sufficient current. The convenient in-line type power supply reduces clutter at the A/C source and is easy to position away from signal carrying cables to reduce induction. A cable lock is provided to ensure the power supply is not accidentally disconnected.
Using the JDV is the same as any other direct box. Connect the instrument to the input, the amplifier output to the amplifier and the XLR balanced output to the mixer or pre-amp. The XLR output is ‘mic level’ to allow the JDV to be used in snake systems with microphones and splitters. One should note that since the JDV is a ‘unity gain’ device, driving a high level signal into the JDV will result in a high level at the output. This may exceed the capacity of the microphone input levels. To protect against overload, a 15dB pad at the output is provided.  
The real fun with the JDV starts when multi-amp set-ups are created and recording the combination of direct and mic’ed signals are realized. For a full description of functions, the Radial JDV owner’s manual should be perused.


The Radial JDV Super DI is truly an innovative product that lives up to its name. With its unique Class-A feed-forward circuit design and high internal rail voltage, it produces exceptional dynamic handling without introducing distortion or color. It features a full compliment of input and output connections to present greater creative options, all the while retaining the original sound that has made the JDV one of the most highly acclaimed and recorded direct boxes of all time.


User Manual


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