Radial Engineering Headload Prodigy User manual

True to the Music
www.radialeng.com
®
True to the Music
®
User Guide
Headload Prodigy
Load Box and Amp DI
www.radialeng.com
Radial Engineering Ltd.
1588 Kebet Way, Port Coquitlam
British Columbia, Canada, V3C 5M5
tel: [phone] • fax: [phone]
email: [email protected]
™

This page left blank.
CAUTION!
The Headload Prodigy is a load box that is designed to safely handle and attenuate up
to 120 watts RMS of power from a guitar or bass amplier. The Headload Prodigy is
intended for 8 Ohm. For best performance and proper power transfer, NEVER EXCEED
THE PRODIGY’S 120 WATT POWER RATING and always match the impedance. Ex-
ceeding this power can cause the Headload prodigy to overheat which could damage
the unit. The Headload Prodigy speaker connections employ switching jacks that reroute
the signal to the amp and/or internal load resisters. DO NOT DISCONNECT CABLE AT
SPEAKER BOX END AND LEAVE IT CONNECTED TO THE HEADLOAD PRODIGY.
! !

Headload Prodigy™ Load Box
True to the Music
®
Radial Engineering Ltd.
Radial®Headload ProdigyTM
Load Box and Amp DI
Table of Contents Page
Feature set ..............................................................................................................1-2
Making Connections ...................................................................................................3
How to Use ..............................................................................................................4-5
JDX Balanced Output .................................................................................................6
JDX Unbalanced Output .............................................................................................7
Using the Features ..................................................................................................8-9
Rack Mounting and Cable Length ............................................................................ 10
Block Diagram .......................................................................................................... 11
Specications ...........................................................................................................12
Warranty .................................................................................................... Back Cover
Thank you for purchasing the Headload Prodigy. The Prodigy is a multi-purpose load box
that enables you to reduce the output of your speaker cabinet and to send your guitar amp
and cabinet sound to the PA or recording system using the built-in JDX direct box output.
You can simultaneously set your amp to full output, half volume, or turn it completely off for
quiet on-stage performance or late night recording.
Best of all, the Prodigy has been designed to be straight forward and easy to use. However,
as with all products, making sure you understand the features will not only improve your
musical experience, it will ensure your equipment is safe from damage due to misuse. So
please take a few minutes to read through this manual to familiarize yourself with all of the
built-in features.
If after reading, you nd yourself looking for more answers, please visit the Prodigy FAQ
page on the Radial web site. This is where we post updates and questions from users like
yourself. If you still do not nd what you are looking for, feel free to send us an email at
[email protected] and we will do our best to reply in short order.
Now get ready to rock out at full, half or no volume at all.

Radial Engineering Ltd. Headload Prodigy™ Load Box
True to the Music
®
FRONT PANEL FEATURE SET
1
1. HEADPHONE: ¼” TRS mono summed output for headphones lets you quietly practice
while your amp is being driven hard.
2. PHONES: Variable control used to adjust headphone level to suit.
3. LINE OUT: Variable control to adjust the level going to the unbalanced ¼" JDX outputs.
4. EQ: Lets you ne tune the tone of the JDX output to optimize your wedge monitors or
in-ears.
5. POL 180: Inverts phase by toggling pin-2 and pin-3 at the XLR out to correct acoustic
resonance or to help phase-align the direct out with a microphone.
6. POWER: LED indicator lets you know the Prodigy is activated.
7. HANDLE: Makes it easy to carry your Prodigy around the studio – may be removed for
rack mounting.
8. STEEL CASE: Solid 14-gauge steel outer shell shields the inner electronics from
disruptive magnetic elds generated by the amplier’s power transformer.
9. VENTS: Top access ventilation slots allow excess heat to be dissipated without the
need of a fan.
10. BOOK-END DESIGN: Creates protective zone around the switches and potentiometer
to keep them out of harm’s way.
1 2 3 4 5 6
8 9 10
7

Headload Prodigy™ Load Box
True to the Music
®
Radial Engineering Ltd.
REAR PANEL FEATURE SET
2
11. BALANCED OUT: JDX lo-Z balanced mic level output used to feed the PA system,
monitors or recorder.
12. GND LIFT: Lifts pin-1 on the XLR output to help eliminate hum and buzz caused by
ground loops.
13. POST-EQ: Presents a post JDX and post (wet) EQ output to feed a second direct box
for recording or external effects processor.
14. PRE-EQ: Pre-JDX direct output sends the unaffected (dry) direct signal from your amp
to feed another stage amp or effects.
15. 100% OUTPUT: ¼” output delivers full output of your amp to the speaker cabinet.
16. FROM AMP: ¼” input connects signal from your amp head output to the Prodigy.
17. 50% OUTPUT: ¼” output is used to attenuate the volume for quiet on-stage
performance.
18. POWER: Connection for the external 15VDC 400mA power supply.
19. CABLE CLAMP: Secures the DC adapter cable to prevent accidental power
disconnect.
11 12
13
14 15 16 17 18
19

Radial Engineering Ltd. Headload Prodigy™ Load Box
True to the Music
®
3
MAKING CONNECTIONS
Before making any connections, make sure your guitar amp is turned off and the audio system
is either turned down or volume levels turned off. This will protect sensitive components such
as tweeters and speakers from turn-on or connection transients. If you are connecting to a
preamp or mixer, make sure the 48V phantom power is turned off as it is not required. Always
use heavy 14-gauge speaker wires (or heavier if possible) between the Headload Prodigy and
your amplier to ensure optimal signal ow from the head to the speaker cabinet.
The Prodigy does not have a power switch. As soon as you connect the power supply, it will
automatically turn on and the front panel power LED will illuminate. A handy cable clamp is
provided that can be used to secure the power supply if needed. Simply loosen with a hex
key, slip the power supply cable into the cavity and tighten.
Set the Prodigy controls to the start position with the tone controls to 12 o’clock, the two level
controls to off (7 o’clock), and the ground lift and polarity reverse switches in the outward
position. The rear panel ground lift switch is recessed to prevent accidental changes during
a show. To activate, use a small screwdriver.
Use a hex driver to
loosen the cable lock.
Pass the cable through
and re-tighten.
GND LFT in 'out' position

Headload Prodigy™ Load Box
True to the Music
®
Radial Engineering Ltd.
HOW TO USE THE PRODIGY
As the Prodigy may be used in three different ways, it is important that you rst determine
how you plan to use it before making connections.
1. As a simple direct box
2. For 50% attenuation
3. For silent performance
1. Using the Prodigy as a Simple Direct Box
Used this way, the Prodigy acts as an interface that lets you send the sound of your amp using
the built-in Radial JDX™ balanced output to the PA or recording system. This takes advantage
of the reactive load that captures both the sound of your amp head and the back-electromotive
impulse from the loudspeaker. It has no audible effect to your amp sound.
a. Connect the output from your amp to the Prodigy FROM AMP ¼” input
b. Connect the 100% output from the Prodigy to your speaker cabinet
c. Connect the XLR output from the Prodigy to the PA mixer or recording preamp
d. Connect the power adaptor to the Prodigy to turn it on – there is no power switch
e. Power up your amp and slowly increase the volume
4
FOOTPEDAL
WARNING!:RISK OF HAZARDOUS ENERGY
AVIS!:ENERGIE ELECTRIQUE DANGEREUSE!
!
SPEAKERS
Speaker Input
Back view of amp
FOOTPEDAL
WARNING!:RISK OF HAZARDOUS ENERGY
AVIS!:ENERGIE ELECTRIQUE DANGEREUSE!
!
SPEAKERS
Speaker Input
Back view of amp

Radial Engineering Ltd. Headload Prodigy™ Load Box
True to the Music
®
5
3. Using the Headload Prodigy to silence your amp
This setting turns off your guitar amp’s speaker cabinet completely for silent performance.
This works great for gigs where you do not want to haul a speaker cabinet to the show or for
quiet late-night recording in the studio. This takes full advantage of the built-in JDX speaker
simulator to capture your amplier’s tone and the load box to keep your amp safe and quiet.
a. Connect the output from your amp to the Prodigy FROM AMP ¼” input
b. Do not connect the output from the Prodigy to your speaker cabinet
c. Connect the XLR output from the prodigy to the PA mixer or recording preamp
d. Connect the power adaptor to the Prodigy to turn it on – there is no power switch
e. Power up your amp and slowly increase the volume
When testing, it is good practice to keep the volume level down low to ensure proper connec-
tions have been made before turning up. This can prevent connection spikes from damaging
sensitive components.
AMP
MIXER
AMP
CAB
MIXER
2. Using the Prodigy to attenuate your amp by 50%
Here, the Prodigy reduces the output level on your amp so that it sounds about half as loud
as usual. This lets you drive the power amp section of your amp harder to optimize the tone
while lowering the volume level on stage or in the studio. Engineers will sometimes combine
the JDX output with a mic in front of the cabinet and mix the two sounds.
a. Connect the output from your amp to the Prodigy FROM AMP ¼” input
b. Connect the 50% output from the Prodigy to your speaker cabinet
c. Connect the XLR output from the prodigy to the PA mixer or recording preamp
d. Connect the power adaptor to the Prodigy to turn it on – there is no power switch
e. Power up your amp and slowly increase the volume

Headload Prodigy™ Load Box
True to the Music
®
Radial Engineering Ltd.
THE JDX BALANCED OUTPUT
The Headload Prodigy’s JDX balanced output is designed to simulate the sound of a 4 x 12
half stack. This lets you capture your sound ‘direct’ without having to use a microphone. The
benets to performing and recording this way are numerous. Moving a microphone ever so
slightly will change the sound, so getting it exactly the same every night or for every session
is practically impossible. Further, each time you change venues, resonant frequencies caused
by the stage and room acoustics vary, which means that EQ’ing the tone to get it right has
to be redone every show. Finally, noise pollution from the other instruments on stage, such
as bass or drums, entering the mic makes it difcult to solo the instrument. With the Prodigy
direct out, all of these problems simply go away. You get consistency night after night, gig
after gig, and from one recording to the next.
The JDX output is set to mic level in order to match up with other mics on stage. This makes
it possible to feed a traditional snake or mic splitter, which in turn can feed the PA, wedge
monitors and in-ear monitors.
In the studio you can record as usual with a mic and record a second channel using the JDX
output. This lets you compare or combine the two signals to create richer and more consis-
tent tones. You can take things further by introducing a Radial Phazer™ into the equation by
phase correcting the direct JDX signal so that it is time-aligned with the mic. The Prodigy is
a creative tool that should be used to experiment.
6
PHAZER
DIRECT SIGNAL DIRECT SIGNAL
TIME ALIGNED
MIC SIGNAL

Radial Engineering Ltd. Headload Prodigy™ Load Box
True to the Music
®
7
USING THE JDX AUX OUTPUTS
There are two additional ¼” unbalanced outputs on the rear panel. These provide connectivity
options that can open the door to new sounds or creative ideas. A dedicated front panel level
control lets you adjust the signal for both outputs to suit.
• Direct Output (pre-JDX)
This takes the original 'dry' sound from your guitar amp head and attenuates it so that it
can be used to drive another guitar amp, digital modeling device, effects pedals, or maybe
a JDI direct box so that you can then process the sound in your digital workstation or
reamp it in the future.
• Wet Output (post-JDX)
This parallel output produces the same processed or 'wet’ signal as the JDX – only here
it is unbalanced. This means that the front panel EQ will also affect this output. It can be
used to feed effects pedals, digital modeler or maybe some other innovative studio device.
AMP
POST EQ
PRE EQ
CAB

Headload Prodigy™ Load Box
True to the Music
®
Radial Engineering Ltd.
8
USING THE PRODIGY FEATURES
Adjusting the Tone Using the 2-band EQ
The Prodigy is equipped with a two band equalizer that lets you ne tune the tone of the JDX
output. It has no effect on the amplier’s speaker signal. Used live, this lets you adjust the
tone of the wedge monitors on in-ears to suit. In the studio, it lets you quickly tailor the tone
as needed. Start with the EQ settings at 12 o’clock and adjust as you see t.
Using Headphones
Finally, one of the coolest features on the Prodigy is the headphone out which will work with
most headphones from 8 Ohms to 400 Ohms and lets you quietly practice using your amp to
create the signal. It is equipped with a dedicated level control and ¼” TRS connection. Note
that the headphone output is mono.
20 20k50 100 200 500 1k 2k 5k 10k
Hz
+20
+15
+10
+5
0
-5
-10
-15
-20
dBu
EQ Frequency Response Range
Frequency response
with at EQ settings
Frequency response
of EQ range

Radial Engineering Ltd. Headload Prodigy™ Load Box
True to the Music
®
9
The 180º Polarity Reverse Switch
The Headload Prodigy’s JDX output is wired to the AES standard with pin-1 (ground), pin-2 (+),
and pin-3 (-). This follows convention with all pro audio gear made in recent years. But when
combining the JDX with older vintage gear, you may nd that the input on your vintage processor
may have the polarity reversed. To address this, the Prodigy is equipped with a 180º polarity
reverse switch that toggles pin-2 and pin-3 at the XLR output, inverting the relative phase.
The polarity reverse function can also be used to compensate for ‘acoustic peaks and val-
leys’ at certain spots on stage that can cause some frequencies to sound louder than others
due the interaction of the amp, monitors and PA. Switching the polarity can sometimes help
normalize the sound where you may be standing.
Finally, when recording, placing a mic in front of the cabinet and then further away will change
the tone depending on room acoustics and the effects of comb-ltering. Combining the mic'd
sound with the Prodigy’s JDX direct output can lead to great results. Try reversing the polarity
to improve the phase relationship between the two signals and then, for fun, try moving the
distant mic around. Simply nd the setting that sounds best to your ears.
Using the Ground Lift
A common problem in both studios and live PA is the hum and buzz that seems to propagate
as soon as various pieces of audio devices are connected together. This problem is often
referred to as a ground loop. In general terms, when plugged in to the electrical system,
for safety, all of the devices share the same electrical ground. When an audio connection is
made, the audio ground creates a loop that allows noise from spurious DC currents and other
‘gremlins’ to pollute the audio signal.
To help eliminate the hum and buzz caused by ground loops, the Headload Prodigy is
equipped with a ground lift switch that lifts pin-1 on the XLR output. If you hear hum, push
the switch inward. The switch is recessed in order to prevent accidental use. To switch, use
a small screwdriver.

Headload Prodigy™ Load Box
True to the Music
®
Radial Engineering Ltd.
10
RACK MOUNTING THE PRODIGY
For touring, the Prodigy may be mounted into a standard 19” rack using the optional rack
mount kit. This three piece kit (part number: R800 2020 02) enables one or two Prodigy to
be rack mounted in a 1RU rack space. We recommend leaving one rack space open above
the Prodigy to allow air ow.
Single unit mounting: Double unit mounting:
Cable Length 100 Watt Amp
8 Ohms
100 Watt Amp
4 Ohms
50 Watt Amp
8 Ohms
50 Watt Amp
4 Ohms
1.2 meters (4’) 1.0mm2(16 awg) 1.0mm2(16 awg) 1.0mm2(16 awg) 1.0mm2(16 awg)
2.4 meters (8’) 1.5mm2(14 awg) 1.5mm2(14 awg) 1.0mm2(16 awg) 1.5mm2(14 awg)
3 meters (10’) 1.5mm2(14 awg) 2.5mm2(12 awg) 1.5mm2(14 awg) 1.5mm2(14 awg)
3.7 meters (12’) 2.5mm2(12 awg) 2.5mm2(12 awg) 1.5mm2(14 awg) 2.5mm2(12 awg)
4.9 meters (16’) 2.5mm2(12 awg) 4.0mm2(10 awg) 1.5mm2(14 awg) 2.5mm2(12 awg)
5.5 meters (18’) 4.0mm2(10 awg) Do not use 2.5mm2(12 awg) 2.5mm2(12 awg)
6.0 meters (20’) Do not use Do not use 2.5mm2(12 awg) 2.5mm2(12 awg)
CONNECTING THE AMPLIFIER AND SPEAKER
You can connect ampliers up to 120 Watts RMS (180W peak) to the Prodigy and drive
them at full power. We recommend using speaker cables eight feet or less in length with a
minimum gauge of 1.5mm2 (14 awg). Longer speaker cables should use heavier gauges to
maintain the best power transfer. Use the chart below as a guide when selecting speaker
cables to use with your Prodigy.

Radial Engineering Ltd. Headload Prodigy™ Load Box
True to the Music
®
BLOCK DIAGRAM
*Specications are subject to change without notice.
FROM AMPLIFIER
SPEAKER
OUTPUT
THROUGH
TO LIVE
SPEAKER
CABINET
LINE
OUTPUT
SPEAKER
50% LEVEL
OUTPUT
VARIABLE
ATTENUATOR
WITH
LOAD BANK
ATTENUATOR
GROUND
LIFT
BUFFER/
EQUALIZER
BUFFER/
EQUALIZER
LOW FREQUENCY
HIGH FREQUENCY
LOW PASS
FILTER
PHASE
INVERTER
PHASE
REVERSE
OUTPUT
BALANCED
HEADPHONE
AMPLIFIER HEADPHONE
OUTPUT
LINE
AMPLIFIER LINE
OUTPUT
LINE
LEVEL
HEADPHONE
LEVEL
11

Headload Prodigy™ Load Box
True to the Music
®
Radial Engineering Ltd.
*Specications are subject to change without notice.
OUTPUT SIGNAL FLOW
AMP
JDX LOW / HIGH
EQ
HEADPHONE
LEVEL
UNBAL. OUT
PRE-EQ
HEADPHONES
POST-EQ
JDX BAL. OUT
POST-EQ
JDX UNBAL. OUT
POST-EQ
SPEAKER OUT
50%
SPEAKER OUT
100%
ATTENUATIONPRODIGY
Audio Circuit Type: ........................................Passive attenuation circuit with active equalization
Frequency response:......................................Shaped to emulate a classic guitar cabinet
Gain:...............................................................-30dB/-42dB
Noise oor: .....................................................-106dBu
Maximum input: ..............................................130 watts continuous
Total harmonic distortion: ...............................0.05%
Intermodulation distortion: .............................0.05%
Input / output impedance: ..............................8Ω speaker load
Output level - max - 1KHz: ............................+17dBu
Output level - max - 20Hz: .............................+14dBu
Size (W, D, H) & weight:.................................6” x 10.25” x 3.75”
........................................................................152mm x 260mm x 95mm
Weight: ...........................................................5.3lbs. (2.4kg)
Power supply:.................................................+/-15v (400mA) power supply
SPECIFICATIONS
12

www.radialeng.com
THREE YEAR TRANSFERABLE LIMITED WARRANTY
RADIAL ENGINEERING LTD. (“Radial”) warrants this product to be free
from defects in material and workmanship and will remedy any such de-
fects 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 nish 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. In
the unlikely event that a defect is uncovered, please call 604-942-1001
or email [email protected] to obtain an RA number (Return Autho-
rization number) before the 3 year warranty period expires. The product
must be returned prepaid in the original shipping container (or equivalent)
to Radial or to an authorized Radial repair center 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 and transferable warranty. This warranty
shall not apply if the product has been damaged due to abuse, misuse,
misapplication, accident or as a result of service or modication by any
other than an authorized Radial repair center.
THERE ARE NO EXPRESSED WARRANTIES OTHER THAN THOSE
ON THE FACE HEREOF AND DESCRIBED ABOVE. NO WARRANTIES
WHETHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMIT-
ED TO, ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FIT-
NESS 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, 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 DEPENDING ON WHERE YOU
LIVE AND WHERE THE PRODUCT WAS PURCHASED.
Radial®Headload Prodigy™ User Guide - Part #R870 1208 00
Specications and appearance are subject to change without notice.
Radial Engineering Ltd.
1588 Kebet Way, Port Coquitlam BC V3C 5M5
tel: [phone] • fax: [phone]
[email protected] • www.radialeng.com