Radial JDV Mk3 Direct Box
Radial Engineering
1638 Kebet Way, Port Coquitlam BC V3C 5W9
tel: 604-942-1001 · fax: 604-942-1010
email: info@radialeng.com web: www.radialeng.com
engineering
Owner’s manual
www.radialeng.com
Radial Engineering - 1638 Kebet Way, Port Coquitlam BC V3C 5W9
tel: 604-942-1001 · fax: 604-942-1010 email: info@radialeng.com
Radial Engineering is a division of JP Cabletek Electronics Ltd.
www.radialeng.com
engineeringengineering
PLEASE READ BEFORE CONNECTING ELECTRONIC DEVICES TO YOUR JDV!
Caution must be used when connecting electronic equipment to the
JDV Mk3. The JDV Mk3 bridges all electronic equipment connected
to it so faulty wiring or incorrect grounding of any of the equipment
may cause a shock hazard to be present and/or damage to the JDV
or other connected equipment. Because grounding schemes differ
between manufacturers, it is important to check for correct polarity,
in particular with older amplifiers using 2-prong ungrounded A/C
cords. If the polarity is reversed on an ungrounded amplifier there
may be a potential of 120V present between the amp chassis and
ground. Radial Engineering takes no responsibility for this or how
the JDV is connected or used. It is the users full responsibility to
ensure that proper electrical polarity is maintained on all equipment
connected to the JDV and that proper building electrical codes have
been followed wherever the JDV is being used.
To reduce opportunity for shock hazard or damage to the JDV or
connected equipment, plug the ¼” connectors into the amplifiers
first and then to the JDV. This is especially important when using old
amplifiers that do not have 3-prong plugs as the possibility exists to
touch the chassis ground with the connector plug tip when the plug
is inserted into the jack.
Cautions for amplifiers with ungrounded 2-prong A/C cords:
Before connecting the JDV to an ungrounded amplifier, power the
amp up and listen to the residual hum. If the amp has a two-position
ground polarity reverse switch, set the switch in the position that
produces the least residual hum from the speakers. If there is no
polarity switch, reverse the A/C plug at the outlet to find the least
residual hum.
To ensure an ungrounded amplifier does not present a shock
hazard: Test for voltage potential by connecting a voltmeter
between the amplifier chassis and the JDV chassis. If voltage is
present, reverse the amplifier’s A/C supply polarity and test again.
Note that due to this potential problem, damage to the JDV or other
connected equipment caused by improper A/C polarity is not
covered under warranty.
>>>>>>>> CAUTION <<<<<<<<
Introduction
It is with great pleasure that we welcome you to our extended family of Radial
direct box owners. We are extremely proud of the Radial JDV Mk3 and are
confident that you will find this device to sound great, be fun to use and above
all, be a useful tool in advancing your music.
The new Radial JDV Mk3 features the same highly praised Class-A audio
circuit that was in the original JDV with several improvements in areas
such as lower noise, higher rail voltage and subsequent dynamic range. You
will also notice major changes with respect to input and output signal
management.
As there are many interesting features that are not found on any other direct
box, we highly recommend reading this manual before you start using your
new JDV. By doing so you will gain a full understanding of the philosophy
behind the product design and enjoy better all-round results.
Enjoy!
For more information, questions or comments, please contact Radial
Engineering at the address below or email: info@radialeng.com
Radial Engineering 1638 Kebet Way, Port Coquitlam BC Canada V3C 5W9 tel: 604-942-1001 · fax: 604-942-1010
email: info@radialeng.com web: www.radialeng.com Radial Engineering is a divisio n of JP Cabletek Electron ics Ltd.
Table of Contents: Page(s)
Design Concept........................ ............................ ............1
The Magic Behind Great Sound............... ..........................2
What Is a Direct Box Anyway?............................... ............2
Instrument and Amp Matching................................ ............3
Control Panel............................ ..................................4 ~ 5
Connector Panel .................................................. ......5 ~ 6
Balanced Output Panel ........................... ..........................6
Powering Up .......................................... ..........................7
Setups.................................................... ..................9 ~ 12
Questions & Answers.............................. ................13 ~ 15
Specifications and Block Diagram ........................... ..........16
Warranty and Safety Information ............................back cover
Radial JDV Mk3 Direct Box
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JDV Mk3 Owner’s Manual
PLEASE READ CAUTION
ON BACK COVER
www.radial .comeng
JDV Mk3 Owner’s Manual
engineeringengineering
RADIAL LIMITED THREE YEAR WARRANTY
Radial Engineering - a division of JP Cabletek Electronics Ltd. ("Radial")
warrants this product to be free from defects in material and workmanship to the
original owner and will remedy any such defects free of charge according to the
terms of this warranty. Radial will repair or replace (at its option) any defective
component(s) of this product (excluding finish and wear and tear on components
under normal use) for a period of three (3) years from the original date of
purchase. In the event that a particular product is no longer available, Radial
reserves the right to replace the product with a similar product of equal or greater
value. To make a request or claim under this limited warranty, the product must be
returned prepaid in the original shipping container (or equivalent) to Radial or to an
authorized Radial repair centre and you must assume the risk of loss or damage.
A copy of the original invoice showing date of purchase and the dealer name must
accompany any request for work to be performed under this limited warranty. This
limited warranty shall not apply if the product has been damaged due to abuse,
misuse, misapplication, accident or as a result of service or modification by any
other than an authorized Radial repair centre.
THERE ARE NO EXPRESSED WARRANTIES OTHER THAN THOSE ON THE
FACE HEREOF AND DESCRIBED ABOVE. NO WARRANTIES WHETHER
EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO, ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR
PURPOSE SHALL EXTEND BEYOND THE RESPECTIVE WARRANTY
PERIOD DESCRIBED ABOVE OF THREE YEARS.
RADIAL SHALL NOT BE RESPONSIBLE OR LIABLE FOR ANY SPECIAL OR
INCIDENTAL OR CONSEQUENTIAL DAMAGES OR LOSS ARISING FROM
THE USE OF THIS PRODUCT. THIS WARRANTY GIVES YOU SPECIFIC
LEGAL RIGHTS, AND YOU MAY ALSO HAVE OTHER RIGHTS, WHICH MAY
VARY, FROM STATE/PROVINCE TO STATE/PROVINCE.
Radial Engineering 1638 Kebet Way, Port Coquitlam BC Canada V3C 5W9 tel: 604-942-1001 · fax: 604-942-1010
email: info@radialeng.com web: www.radialeng.com Radial Engineering is a division of JP Cabletek Electronics Ltd.
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JDV Mk3 Block Diagram
JDV Mk3 Owner’s Manual
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1
The Radial JDV Mk3 takes this concept to a completely new level by providing
the musician and engineer with greater flexibility than ever before and does so
without any signal degradation whatsoever. The concept is simple: We have
broken down the signal path into three zones:
(1) Instruments, (2) Musician’s setup, (3) Engineer’s setup.
Each ‘zone’ features expanded functionality: Dual inputs allow two instruments
to be selected without having to reconnect. By offering several instrument thruputs, the musician can now work inside his own 'creative world' giving him
greater freedom to create new sounds and inspired results. These include a
standard thru-put for a traditional amplifier, two unity-gain auxiliary outputs to
drive a stereo rig, an effect device or simply more amps. A designated tuner
output allows constant frequency monitoring while being outside the primary
audio signal chain. For the engineer, a standard balanced XLR output provides
the dry instrument signal to track.
One may ask: “This seems so easy and natural, I wonder why no one has ever
done this before?” Truth is that although it may look easy on paper, the challenge
is retaining the signal integrity without degradation. The JDV does this with
virtually zero harmonic distortion, phase distortion or inter-modulation distortion.
To make matters even more interesting, matching the buffered outputs to the
thru-put presents yet another challenge. But what is life without challenges?
INSTRUMENT 1
MIXER
TUNER
AUX OUT 2
AUX OUT 1
AMPLIFIER
RADIAL
JDV
INSTRUMENT 2
Radial JDV Mk3 Zoned Concept
Input zone
Engineer’s zone
Musician’s zone
Design Concept
If you think about it, a direct box is
actually a central distribution hub from
which the instrument signal is managed. Most
DI's simply offer an instrument input, a thru-put to
the musician's amplifier and then an output for the mixing
console.
JDV Mk3 DirectBox
JDV Mk3Specificatons
Frequency Response: 10Hz ~ 30kHz (+/-1dB)
Residual Noise: -93dB @ 1V-RMS
Distortion (20Hz ~ 20kHz): < 0.015% @ 1V-RMS (1.2k load)
< 0.5% @ 5V-RMS (without load)
Phase Deviation: < 5º @ 100Hz
Intermodulation Distortion: 0.07% (DIN standard)
Input Impedance: 10kOhms ~ 3.9mOhms
Output Impedance: 600 Ohms
Input Pad (speaker): -30dB
Output Pad: -15dB
Power requirement: Custom 30Volt supply
The Magic Behind Great Sound
With the advent of 24bit/96kHz digital recording, expanding dynamic headroom
while lowering the noise floor has become the 'holy grail' of analogue circuit design.
The Radial JDV begins with a true Class-A design for audiophile quality. Class-A
circuits are preferred over more common push-pull designs (Class A-B) as they
do not introduce harsh zero-cross distortion. Open the JDV and you will see big,
high-voltage discrete components. These are used because they simply sound
better! For example, larger capacitors are able to store more energy than smaller
ones. This means that the audio signal does not starve when pushed to the limits.
But that is not all. The Radial JDV Mk3 is actually a feed-forward design. This
means that unlike traditional circuits that use a feedback loop to stabilize the
signal path, the JDV circuit looks more like a tube design which by all accounts is
nuts! The result however is stunning! Run a square wave through the JDV and
you get perfectly sharp edges without overshoot or ringing.
To further enhance headroom, the JDV employs an unprecedented 30-volt internal
rail voltage for exceptional dynamic signal handling. High output signals are
handled with ease and since it is virtually impossible to overload the JDV, phase,
harmonic and inter-modulation distortions are virtually eliminated. One should
note that the Radial JDV is a unity gain device. This means that whatever you
put in you get out. In fact, the JDV has so much headroom the PAD is located at
the output so that it will not overload your mixer.
To elevate sound quality yet another notch, we have added Drag™ control; an
innovation that we developed while creating the popular Radial JD7 Injector that
essentially recreates the natural tone that is lost when driving buffered outputs to
several amplifiers (more on this later).
At the end of the day, what sets Radial products apart from all others is our
unyielding commitment to quality and our never ending quest to make our
products innovative, and musical.
Ultimately, the magic to great sound comes from the added care during the design
process, better quality parts and a full understanding of how musicians and
engineers work so that the most can be derived. We do everything we can to
make sure that what you put in, you get out.
Nothing added, nothing lost.
What Is a Direct Box Anyway?
Whether in live or studio conditions, connecting an instrument to a mixer requires
matching the high-impedance (high-Z ¼” guitar jack) of the instrument to a
balanced low-impedance (low-Z XLR jack) system. This is the primary task of
the direct box. Proper impedance matching will provide a wider frequency
response, improved dynamics and in most cases significantly less noise.
It is important to note that the output of the direct box is designed to work alongside microphones. Once the instrument signal has been converted to a balanced
low-Z signal (think low resistance), it must drive long cables without appreciable
noise. Concert snake systems employ splitting transformers to bridge the signal to
several destinations such as the front of house (FOH) mixing console, the monitor
mixing console, and sometimes a broadcast or recording truck. These 'bridging'
transformers are designed to work at mic level. Since DI's need to work within
this same environment, the output signal is akin to a 600-Ohm mic level.
Thus the output of a direct box should be connected to a mic input such as found
on mixing consoles or mic preamps. The better the pre-amp, the better the results.
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Why is the speaker pad switch recessed and difficult to get to?
This is a think before action precaution. This is the most dangerous feature on
the JDV. If one connects a speaker output directly to the JDV without a load,
there is a good chance that they will blow the input. By making sure that getting
into this function is difficult, we figure that the user will be aware of what he is
doing and be less prone to make a mistake.
I am not getting much level. What could be wrong?
Check the recessed -30dB speaker pad switch. If this is pushed in, the input
level will be way down. This is usually the offender because it is hard to see.
Also, check the -15dB output pad to make sure it is not depressed.
I am getting too much level, can I use the line level input on my mixer?
Yes. The JDV, being a unity gain device, is able to produce line level output
signals if driven hard.
The sound seems a little muffled in the high-end?
If the Vary-Z is engaged and the Drag control is completely counter-clockwise,
the sound can be muffled as you are dropping the input impedance well below
normal. Also check to make sure the lo-pass filter is not on.
Can I use the Tuner out to drive another amp or effect device?
Yes but the quality of this output will be more along the lines of regular direct
boxes. The TUNER OUT signal is guitar level and is perfectly fine for effects and
having fun. Of course its primary function is to keep you tuned without
allowing the tuner circuit to get in the way of the sound.
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Control Panel
All input controls and visual monitoring are located on the JDV’s input panel.
No connectors are on this panel so clear access to the controls and monitoring is
provided without cables being in the way.
LED Status Indicators
LED status indicators for POWER on, SIGNAL presence and CLIP peak
overload. Normally, the green power LED should be on as soon as the
JDV power supply is connected. The yellow signal presence LED will
flash on and off following the music program while the red overload LED
will light up should the input signal ever exceed the normal operating level.
LO-CUT and HI-CUT Filters
The JDV is outfitted with two filters: The LO-CUT (Hi-Pass filter - cuts
low frequencies thus allows the allows high frequencies to pass) is set at
-3dB@175Hz for a gentle, natural sounding roll-off. Hi-Pass filtering is
used to lessen low-frequency 'mud' that can sometimes cause bass to lose
definition. It is also extremely effective at reducing resonance or rumble
that is common with acoustic guitars during a live performance.
The HI-CUT (Low-Pass filter - cuts high frequencies and allows low
frequencies to pass) is set at -3dB@8kHz providing a simple solution to
reducing hiss and noise from older equipment such as noisy keyboards,
older active acoustic guitars or when using the direct out from noisy
amplifiers.
LED status indicators include
POWER (system on), SIGNAL
(signal present) and CLIP
(peak level overload)
HI-CUT (Low-pass) filter gently rolls
off high end to reduce noise and hiss
from older instruments
LO-CUT (Hi-Pass) filter
cuts low-end rumble, acoustic
resonance and excessive bass
Book-end design
protects switches
and jacks from
damage in realworld environments
14 gauge steel
construction with
baked enamel
coat for maximum
durability
VARY-Z selects between ultra-high
3.9 meg-Ohm input impedance or
variable impedance with Drag control
DRAG™ control is used to recreate
the natural loading and feel of the
instrument pickups on the outputs
Selectable A or B INPUT switch
allows two instruments to be
connected for quick select
20Hz
20kHz
8kHz
175Hz
0dB
-3dB
-6dB
Filter response.
Questions and Answers
What is a direct box anyway?
A direct box is an impedance matching and signal-balancing device. DI's convert
hi-impedance instrument signals to mic-level balanced lines for interface with
pro-audio equipment such as mixing consoles. A good direct box will ensure
proper electrical signals are maintained throughout the signal chain and allow
long cable runs without added noise. A good DI box is just as important as a
good microphone.
What is the difference between active and passive direct boxes?
Active direct boxes require power such as a separate power supply, 48V
phantom power, or a battery to activate their circuits while passive direct boxes
convert the signal from high-Z to low-Z using only a transformer. Passive DI's
do not require a power supply to work.
I heard active direct boxes are better?
This can be thought in terms of a dynamic mic compared to a condenser mic.
There are good dynamic mics and there are good condenser mics. A good
passive direct box depends entirely on the transformer that is being used. For
instance, the Radial JDI uses the world's finest transformer, a Jensen. These DI's
sound fabulous! In fact way better than most active direct boxes!
If the JDI is so good, why should one buy the JDV over the JDI?
It comes down to the application. For keyboards, and simple live set-ups, the JDI
is fantastic. No power supply, no batteries to go dead. You just plug it in and it
sounds great. The JDV on the other hand will give you more reach. You will
enjoy more detail or as Khaliq Glover (Engineer for Marcus Miller and Herbie
Hancock) said: “the JDV is almost holographic compared to the single
dimension of most DIs.”
Can I power the JDV with the 48V phantom on my console?
No. Typical 48V phantom power only has 5 milliamps of available current. The
JDV requires much more current than this to drive its 30 Volt rails. Phantom
power is simply unable to do the job.
Why would I buy the JDV over other active direct boxes?
Sound quality. There is nothing on the planet that will do a better job than the
JDV. It is designed from the ground up to be sonically pure, exceptionally
dynamic, and totally transparent. The combination feed-forward design, class-A
circuit and 30 volt internal rails combine to put the JDV in a class of its own.
Why is Class-A considered best?
Class-A circuits do not employ multiple gain stages to achieve greater efficiency.
They are pure gain stages that have and continue to be the choice for audiophiles
and purists. Although more efficient, Class-B or AB circuits suffer a problem
called zero-cross distortion that Class-A devices do not. In the JDV, we are not
concerned about power-per-watt output, we are only concerned about getting the
best possible sound. We go a step further in employing a unique feed-forward
design.
What is a feed-forward design?
The 'easy guide' to circuit design always includes a feedback loop in the circuit
to stabilize the circuit. The JDV does not take the easy way out; there is no
feedback loop. The JDV circuit is akin to a pure tube circuit design. The result
is razor sharp precision without overshoot, ringing or rounded-off wave
generation. This things is almost alive!
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JDV Mk3 Owner’s Manual
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-30dB Parallel Speaker Pad
Sometimes, it may be desirable to tap the signal from the speaker cabinet to
get the sound of the instrument after the amplifier (post effect). The JDV is
equipped to do so by inserting a -30dB input pad into the circuit..
Using a speaker-tapped signal can be fun however it should be noted that
the signal from the guitar amp is designed to drive 12” and 15” instrument
speakers which mask high frequencies (no tweeters). Because of the extreme
fidelity of the JDV, it is possible that residual noise content from the amp
and the speaker 'hang-over' effect will be audible. Try using the JDV’s highfrequency roll-off (HI-CUT filter) or adjust EQ to suit.
To activate the -30dB pad, depress the recessed ‘PAD-30dB’ switch using a
pen or small screwdriver, then connect the signal from the speaker cabinet or
the amplifier’s second speaker output using a regular speaker cable. Failure
to connect a speaker or load box in parallel to the JDV may cause
severe damage to the JDV and/or the amplifier which would not be
covered under warranty.
Balanced Output Panel
BALANCED OUTPUT
600 Ohm mic level XLR-M output connector wired to the AES (pin -2 hot)
standard connects to mixer or mic pre-amp input.
POLARITY 180º Reverse
Switches XLR pin-2 (normally hot) with pin-3, useful when interfacing with
older equipment wired with pin-3 hot. Also a useful creative tool in the
studio. When mic'ing an amplifier and recording a direct signal, reversing
the polarity can lead to some very interesting and fun effects - try it!
GROUND Lift
Switch lifts the ground path from the JDV to the mixer. When depressed,
the JDV ground is solely connected to the guitar amp and/or aux outputs.
-15dB Pad
As the JDV is a unity-gain device with an exceptionally high internal rail
voltage, a powerful input signal will produce a powerful output level. As
the JDV’s output can often exceed the input capacity of many mixing
consoles, a -15dB output pad is provided to ensure it does not overload the
input.
BALANCED OUTPUT provides
to mixing desk600 Ohm signal
POLARITY 180 everse
flips pin-2 and pin-3
º R
GROUND switch lifts ground at
the XLR from JDV to mixer
PAD - 15dB Output pad reduces
level to prevent mixer overload
POWER 30V-DC
connection jack for
the JDV’s special
power supply
Made in Canada
by fanatics
IMPORTANT: The Radial JDV is NOT a load box and can not handle the
power coming out of an amplifier head on its own. A speaker or properly
matched load box must be connected to the amp before connecting the JDV.
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In this set-up, if ground hum is encountered, lift the ground to the mixer with the
ground lift switch. The JDV will now derive its safety ground from the amp. For
safety, make sure you only use amplifiers with proper 3-pin U-grounds!
Reversing polarity can have dramatic effects on stage if the bass is also in the
stage monitors. Polarity reverse only affects the XLR output. Try in-phase first,
then reversing polarity. It may sound better or widen the players sweet spot.
Activating the LO-CUT (High-Pass) filter can help reduce low-end rumble and
help clean up the mud which often is difficult to manage in large PA systems.
Acoustic guitar set-up
One of the most important features of the JDV is its ability to handle extreme
transients without overloading. Guitar players often drive the pre-amps on their
acoustic guitars above the nominal 0dB level and then push it further by
increasing treble or bass. What few realize is that a mere 3dB increase is actually
increasing the headroom demand by twice the power at that frequency. The
JDV's 30Volt internal rail system is able to handle these demands without a
whimper making it a great choice for acoustic guitars on live stages.
Use the bass guitar set-up described previously. Use of the LO-CUT (Hi-Pass) is
recommended to reduce rumble. Test for best polarity setting as above.
Keyboards
The JDV is perfectly fine for use with electronic keyboards. In fact, the JDV's
sonic performance is superior to what most of these are able to generate. Where
the JDV will shine will be on very dynamic sounds such as grand-piano
samplers where the frequency response is very wide, harmonics are rich and
amplitude variations extreme. Use the same setup as described in Set-up 1 or 2,
depending on whether or not an instrument amp is used.
Driving more than one amp
One of the more exciting aspects of the JDV Mk3 is its ability to drive
several amplifiers or devices at the same time. This expanded functionality
provides freedom to build new sounds that spur the creative process.
The Radial JDV makes this possible and easy by providing two active outputs
designated Aux-A and Aux-B. These are transformerless Class-A feed-forward
outputs that have been designed to reproduce the instrument without adding
artifact. At this stage, it is important to understand how Drag™ control works
and when it would be appropriate to use it (see ‘Drag Control’ on page 5).
The most common application would be driving a stereo amplifier rig.
Important Note: 3-pin U-ground plugs did not exist in the ‘50’s and early ‘60’s
and, as great as they sound, the amplifiers of those days were never designed to
be combined together as we often do now. You may find using un-grounded
equipment a problem because of noise from hum and buzz. For more advanced
or difficult set-ups, check out the Radial JD7 Injector. It is equipped with
isolation transformers as a means to solve some of these electrical challenges.
Connect the JDV's two auxiliary outputs to the stereo rig or two amps. As these
outputs are not transformer isolated, both amps should have grounded A/C cords
in electrical phase and be connected to the same power bar as the JDV. This will
reduce possibility of electrical shocks and noise caused by ground loops. For
safety, please observe correct grounding, check for shock potential with a
voltmeter and/or consult with a trained technician.
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scope of this manual, we recommend that users take the time to access the
wealth of information available on this subject on the web, at the library or by
consulting with recording engineers or collegues. The following are some
pointers to get you started.
Ground Loops
When connecting several pieces of equipment together, a common problem is
ground hum and noise caused by what is commonly known as ground loops.
These are usually caused by electrical phase inversions, by common-mode noise
or voltage differential between equipment.
The JDV is equipped with a ground lift switch that lifts the ground connection
from the JDV to the mixer at the balanced XLR output. The JDV employs a
floating ground scheme and as such must be grounded at either the input or the
output.
For instance, if you are using the JDV with an acoustic guitar and connecting
directly to the mixer without using any of the ¼” output connectors, the ground
lift should be in the out position so that a safety ground to the mixer is
galvanized. If on the other hand you are using the ¼” outputs, the ground lift can
be 'lifted' (depress the switch) as the JDV will now be grounded in two places.
A common solution to reduce ground noise is to connect all of the audio
equipment to the same electrical phase. This is easiest accomplished by using a
power bar and a single power outlet. On large stages, touring professionals have
their own 'distros' or power distribution systems that are pre-configured to this
end. We suggest consulting an electrician and a trained audio technician should
you be in a position to rewire your studio.
Induced Noise
Electro-magnetic induction (EMI) is caused by the magnetic field from one
electrical circuit polluting the field of another. Every copper wire, be it low-level
signal or high power voltage, will emit a magnetic field. These wires are also
subject to induced noise from adjacent magnetic fields. The more power going
through the wire, the larger the electro-magnetic field. For instance, power cables
emit a large magnetic field while signal levels do not. In fact, signal level
conductors are either shielded or split into balanced twisted pair configurations as
a means to keep unwanted noise out. Good quality cable is important.
By keeping audio cables away from power cables, you will immediately reduce
the noise floor. If you must cross these, cross them at 90º if at all possible so that
the interaction of their magnetic fields is kept to a minimum.
The Radial JDV comes equipped with a separate DC supply. As commonly
known, power supplies emit magnetic fields, which in turn can cause noise in
audio systems. The advantage of an external supply is less noise inside the JDV's
metal shell. To further reduce magnetic induction, the JDV power supply should
be kept away from any signal carrying cables and equipment.
A Note About Safety and Shock Hazards
When connecting several pieces of equipment together, it is very important to
ensure that proper electrical wiring be maintained. This is most important when
using older equipment in older homes or venues where electrical safety standards
may not have been upgraded to today's standards. Before connecting equipment
together, always ensure all amplifiers or equipment being used are connected to a
proper electrical system and ensure that all equipment is grounded via the A/C
rd
cord’s 3 prong (U-ground). Failing to do so could cause severe damage to your
equipment and/or increased possibility of electric shock.
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Typical Setups
Acoustic guitar without amplifier
The direct connection is the most basic set-up, most often employed in live stage
or studio situations where the musician does not have his own amplifier, and
relies on monitors to hear their instrument.
In this set-up, the VARY-Z switch is normally in the OUT position, as active
instruments will not be affected. For acoustic guitars, we suggest depressing the
LO-CUT (High-Pass) filter switch. This gentle roll off will reduce acoustic
resonance and opportunity for low-frequency run-away feedback without
affecting the tone. The HI-CUT (Low-Pass) filter would only be engaged if the
instrument is generating exceptional high-frequency noise or hiss. The ground
switch should be in the OUT position to ensure proper safety grounding to the
mixer.
Electric guitar in the studio without amplifier
This same connection as shown above is used in the studio for direct recording
of basses and clean guitar tracks. The difference here being that the instrument
may be passive like a traditional Fender Precision Bass. As such, you may want
to engage the DRAG control to recreate the natural loading of the instrument.
Start by turning the DRAG fully clockwise and depress the VARY-Z switch to drop
the input impedance to 1 meg-Ohm. Now turn the control counter-clockwise
until the sound 'feels' right. This subtle effect will depend on the output level of
the pick-ups and creative decision making of the engineer. 12 o'clock is an
average single coil puck-up to a regular amplifier.
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JDV
Mk3
JDV
Mk3
Speaker box parallel connection
Be sure to read the caution on page 6 re: -30dB Parallel Speaker Pad.
Careful... this fun feature can also get you into trouble. We recessed the switch
to make the use of this function deliberate and protect the JDV’s input from
being damaged through accidental (mis)use.
Sometimes, you may wish to get the sound of the bass or guitar after it has gone
through the amplifier. The JDV allows you to tap the sound off the speaker cabinet
to achieve this. This can be a useful solution when mic'ing the amplifier is
impractical. It can also lead to some great sounds when combining mic'ed and
direct signals.
Using a regular speaker cable, connect the signal from the parallel speaker jack
to input-A on the JDV. Use a pen or small screwdriver to activate the recessed
-30dB pad and connect as shown above. The Drag control will have no effect.
Note that most amplifiers have a lot of self-noise. Try using the lo-pass filter to
roll off some of the high frequency noise. Have fun!
Traditional live set-ups
Bass guitar setup
A common use for a direct box is on stage with a bass guitar. This same set-up
is also often used in the studio where the musician's amp may also be mic'ed
alongside the direct feed and then mixed together by the engineer.
The signal goes from the instrument to the JDV, where the thru-put is connected
to the musician's amp and the XLR output is connected to the mixer. To start,
we recommend all switches be in the out position. The JDV thru-put is a passive
output that passes the bass signal directly to the amplifier. With the Vary-Z switch
in the out position, we will present the highest impedance to the instrument and
therefore the least possible loading. (See discussion on loading in page 3 of this
manual). This will provide the most natural sound to an instrument amplifier.
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JDV Mk3 Owner’s Manual
-30dB pad
activated
!
Powering Up
Inside the JDV packing box you will find the JDV, the power supply and the
manual. The connection on the power supply is a 3-pin mini-DIN. You should
not attempt to use any other supply other than the one that comes with the unit.
As we expect the Radial JDV
to be used in 'real-world'
conditions where it may be
dropped, kicked and stacked,
the JDV has been outfitted
with several abuse resistive
features including: A
‘bookend’ design that creates a
protective zone arund the
switches, controls and jacks, a
full bottom non-slip rubber pad that
provides mechanical and electrical
isolation while ensuring the JDV will
stay put, and an innovative cablelocking strain relief.
To use the strain relief, simply loosen
the nut with a hex wrench (Allen key),
pass the cable through the clamp and
tighten. Using the strain relief prevents
accidental un-plugging... a good idea
especially on action-packed stages!
Turning the Radial JDV On
As soon as you connect the power supply to the JDV, it is on. A green LED on
the control panel will light up at this time. Leaving the JDV connected will not
harm the unit. In fact the JDV, like all other electronic audio equipment, will
sound better once it has reached its stable working temperature. This should take
no more than 5 minutes.
Before you start, make sure all levels on your amp and mixer are turned off.
Connecting the JDV in a traditional fashion is simply a matter of connecting the
instrument to the input, the thru-put to the instrument amplifier and the XLR
output to the mixer. Complete connection options are discussed further in this
manual.
We suggest you start by leaving all switches in the OUT position and use inputA to connect the guitar. Now slowly bring up your amp level and then your
mixer level. Signal should be present at both. If you encounter buzz, try lifting
the ground on the JDV. You should now be set to go.
Dealing With Ground Hum and Noise
In developing the Radial JDV Mk3, we took painstaking measures to ensure
noise was reduced to an absolute minimum so that the JDV would be ready for
the most demanding analogue and digital recording environments. To get the
most out of your JDV, it is important to understand how noise can degrade the
signal and how some simple preventative measures can ensure maximum signal
integrity.
Noise, the curse of any audio system, can be greatly reduced by following some
simple rules of thumb using basic electrical principals. As this is beyond the
Use only the JDV’s supplied
power adapter.
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The JDV’s strain relief in action.
JDV Mk3 Owner’s Manual
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JDV
Mk3
JDV
Mk3
If you are using a passive instrument like an old Precision or Jazz bass, a Strat or
a Les Paul, we recommend that you depress the Vary-Z switch and use the
DRAG control to dial-in just the right amount of natural sounding pickup loading.
Start at 12 o'clock and use your ears!
Remember that any post JDV effect you introduce into the signal chain will only
be heard coming from your stereo rig. The original ‘dry’ sound from the
instrument will still appear at the JDV’s XLR output allowing the engineer to
either record a dry track or mix the dry track with the mic'ed amps on stage.
Re-amping using the JDV with a Radial JDI
A common trick used in recording today is to record a dry guitar track and then
send the recorded track back into the guitar amplifier. This allows the guitarist to
listen to various amplifiers and effects while in the control room.
A great solution to re-amplifying over extremely long distances can be achieved
by combining the JDV and the Radial JDI wired backwards. This may sound
strange, but because the JDI is a passive direct box, it employs an impedance
matching transformer that can either be used to transform the signal from high-Z
to low-Z (traditional DI) or from low-Z to high-Z for use when sending a
balanced signal back to a high impedance input such as on a guitar amplifier.
Record a dry track using one of the JDV setups previously discussed, then send
the recorded track into one of the JDV’s high-Z unbalanced inputs (A or B).
Connect the JDV’s low-Z balanced output to the balanced input of the Radial
JDI, and use the high-Z input of the JDI to feed the amplifier.
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JDV Mk3 Owner’s Manual
JDV high-Z
un-balanced input
JDV low-Z
balanced output
JDI using low-Z
output as input
XLR-F to XLR-M
‘turn-around’
To amp using JDI’s
high-Z input as output
JDV
Mk3
JDI
Mk3
JDV
Mk3
DRAG™ Control
‘Drag’ was developed during the R&D phase of the Radial’s JD7 Injector
guitar signal distribution amplifier/router. After many listening tests we
found that the JD7’s output was too perfect. It did not sound right. The
reason was simple: a vintage pick-up signal, when passing through a preamplifier, becomes active and the natural loading or interaction between the
guitar's pick-up and the amplifier's tube input circuitry is lost. Drag control
re-introduces the desired loading effect by providing the user with control
over impedance and resistance.
The JDV's DRAG control is activated by depressing the VARY-Z switch. A
typical vintage Stratocaster to a Fender Twin relationship can be dialed in
at about 10 o'clock. Less Drag (turning the knob clockwise) will open up
the sound and result in more high-frequency content. It is important to note
that you should use your ears to set the Drag control as every amplifier and
every pick-up will be different. The more you play with Drag, the more
you will find that it is extremely musical.
INPUT Selector Switch
To increase functionality, the JDV allows two instruments to be connected
via the A & B ¼” input jacks which are located on the instrument control
panel. Two guitars or basses are often used during a performance for
alternate tuning, different sounds or simply as a spare for a broken string.
The JDV allows the musician to quickly select an instrument by simply
depressing the instrument INPUT select switch, eliminating hassles such as
setting the amp on standby or muting the instrument to avoid connection
popping.
Connector Panel
Amplifier Outputs
Four ¼” outputs are provided on the JDV to provide the musician or engineer
the greatest flexibility for recording or live performance.
DIRECT THRU - Used as the primary output to the guitar amplifier.
AUX-A OUT & AUX-B OUT - Used to drive additional amps and effect devices.
TUNER OUTPUT - Connects to tuner while keeping the tuner out of the audio
circuit. Can also be used to drive an additional amplifier.
PAD -30dB allows
tapping of signal directly
from the speaker cabinet.
Switch is recessed to
prevent accidental use.
All instrument connections
are positioned on the side
panel. This keeps cables
away from the input controls
for improved organization
DIRECT THRU is used to connect
the primary instrument amplifier
INPUT-A is the primary instrument
input. It is selected from the
front panel switch
INPUT-B is used for second
instrument such as spare.
A-B selector on front panel
AUX-A OUT and AUX-B OUT
are used for additional amps,
stereo rigs or effects for added
system flexibility
TUNER OUT may also
be used for an extra amplifier
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The overload LED never goes on. Why?
Because the JDV has such a huge internal rail voltage, instruments are typically
unable to drive sufficient current into the JDV to cause it to overload. Kinda'
like having 12 cylinders on a car. You don't need them until you are racing. Kick
'em in and the extra horsepower makes all of the difference!
Can I overload the JDV's input?
We could only get the JDV input to overload when we drove the output from the
line level of a mixer directly into the JDV and turned the volume up high. It is
unlikely, under normal use, that you will ever overload the JDV.
Can I connect a guitar amp head to the JDV without speakers?
No. The JDV is not a load box. This means that you must connect the amp to a
st
load 1 (like a speaker) and then you can connect the JDV to the load.
Can I connect a guitar amp head to the JDV with a load box?
Yes. However you should be careful to ensure that the load box properly
emulates a speaker. Make sure the -30dB pad is engaged and monitor the JDV's
input to make sure the overload LED does not go on.
What level is the JDV output?
The JDV is a unity gain device. This means that although it is designed to
output a mic level signal, the output can be significantly higher depending on
what input is being sent to it. This is why there is an output PAD on the JDV.
This allows hot signals to be padded down so that they do not overload the input
to mixers or mic level isolation transformers.
Why don't you put the power supply inside the JDV?
Noise. Due to the JDV's abnormally high input impedance, the internal working
level of the JDV is extremely low. This means that we must do everything we
can to ensure unwanted noise stays out of the JDV circuitry. Power supplies tend
to be a major contributor to noise. Keeping the noise outside is a good thing!
What are the differences between the old JDV and the new JDV Mk3?
The original JDV and the new JDV share the same audio circuit topology and
philosophy. Both use the same Class-A feed forward designs. The old JDV used
a rechargeable battery as a primary supply while the new design does not. We
found that although the original JDV worked well, many users were confused
about charging the battery and unless you read the manual, you could get some
pretty awful distortion or worse yet, you would think the unit was defective.
The Radial JDV Mk3 is the third generation JDV and in developing this box, we
set goals in place that included making the unit more user friendly, lowering the
self-noise and expanding the dynamic range. All of the good things that were in
the original have been maintained or wherever possible improved upon.
Obviously the new JDV has many more features. But that is not all: The new
JDV has gone from using SMT (surface mount technology) to the higher
capacity and precision of discreet components. In order to expand the headroom,
we developed a totally new power supply with a floating ground scheme for less
noise, and we got rid of the rechargeable batteries!
Why did you not put a knob on the Drag control?
Originally, the Drag control was supposed to be recessed so that once set, the
control would not be touched. However we found that it was so darn musical
that people would be adjusting it all the time. Because the JDV will probably
live on the floor most of the time, we felt that a knob would stick out and get
kicked and broken. So no knob. Kinda' looks weird at first, but you'll get used to
it.
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3
JDV Mk3 Owner’s Manual
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Instrument and Amplifier Matching
One of the most beneficial features of the JDV is its ability to handle a wide
range of instrument levels and pick-up configurations. Because of the
exceptionally high internal rail voltage, the JDV does not require an input pad
except for excessive levels such as parallel speaker connections. (This is detailed
later in the manual).
It is important to note that even though the JDV can handle any level, to truly
capture the essence and detail of an instrument, a more precise control is
™
required. Thus the reason we have incorporated Drag control.
When a guitar is connected to an amplifier, the amplifier and the pick-up will
interact. In fact, different cables will also affect the tone. This direct loading is a
normal and essential part of what makes a guitar sound the way it does. Lower
output pick-ups such as those found on vintage instruments are most affected.
When, for instance, a bass is connected to a regular direct box and then to the
amplifier, the pickups are no longer driving the bass alone; the signal is split
between the musician's amplifier and the XLR output that is going to the mixer.
In live situations, the mixer can be as far as 300 feet away. This means that
when using a passive direct box (transformer style) the lowly pick-up must drive
the signal all 300 feet while still driving the amplifier. This loading effect can
sometimes cause the instrument to sound listless and lack punch.
Active direct boxes solve the loading problem by presenting the pick-up with a
high input impedance, thus limiting the energy from the pick-up being sent to the
direct-box and sending most of the pick-up's energy to the instrument amplifier.
The higher the input impedance, the more natural the tone going to the
musician's amplifier. Only one problem; the lower the instrument signal to the
direct box, the more difficult it is to amplify the signal to a usable level without
adding noise, phase distortion and inter-modulation distortion. (Nothing good is
ever free!)
Most direct box input impedances range from 10k-Ohms to 1 meg-Ohms while
the JDV is outfitted with a very high 3.9 meg-Ohm input impedance. The JDV
is able to present this unprecedented input impedance due to the ultra-low noise
design and the unique Class-A circuit that can amplify the signal without adding
distortion.
The 3.9 meg-Ohm input was chosen to reduce loading and for use with piezo
pick-ups such as those typically found on stand-up basses. These are normally
in the 3 to 4 meg-Ohm range and thus when used with the JDV provide
optimum impedance matching for best tone.
JDV
Mk3
JDV
Mk3
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