Radial Engineering JDX-48 User's Guide

JDX 48

Amplier Direct Box

User Guide

CAUTION: Please read safety disclosure
statement on the inside cover before
connecting your Radial JDX 48.

Radial Engineering Ltd.
1588 Kebet Way, Port Coquitlam BC V3C 5M5
Tel: [phone] Fax: [phone]
email: [e-mail]

CAUTION STATEMENT

Please read before

connecting your Radial JDX 48

THE JDX 48 IS NOT A LOAD BOX

It is mandatory that your amplier be connected to a loudspeaker or load
box at all times. The JDX 48 does not provide a signicant resistive load
for an amplier to safely operate. Damage may occur to your amp if the
JDX 48 is used without a proper loudspeaker load.

BEFORE CONNECTING OR DISCONNECTING THE JDX 48.

It is your responsibility to conrm the JDX 48 is connected properly before
operating your amplier. If you are unsure about connecting or operating
the JDX 48 consult a qualied technician or see your dealer. Damage
caused by improper operation is not covered under the warranty. See the
back cover for warranty details.

CAUTION - USE OF THE JDX 48 WITH AMPLIFIERS WITH BRIDGED

OR BALANCED SPEAKER OUTPUTS IS STRICTLY PROHIBITED.

Although these types of circuits (typically a type of a class-D design) are
rarely employed on instrument amps. Using the JDX 48 with them can
cause an electrical shock unless the JDX 48 ground lift switch is depressed.
Please consult the amplier manufacturer to ensure the power output
section of your amp is not designed this way. As we have no control over
the use of these amps, for legal liability reasons, Radial Engineering Ltd.
strictly prohibits use of the JDX 48 with such ampliers.

ALWAYS TURN YOUR AMPLIFIER OFF

Radial JDX 48 Amplier Direct Box

Users Guide

Table of Contents Page

Design Concept ............................................................1

Applications ..................................................................2

Feature Set ...................................................................3

Signal Flow ...................................................................4

Making Connections .....................................................5

Using the JDX 48 .........................................................6

Using the JDX 48 with a Microphone ...........................6

Using With the Phazer ..................................................7

Specications ...............................................................8

Warranty ................................................................Back Cover

Congratulations on your purchase of the Radial JDX 48 guitar amp direct
box, a unique tool for recording and performing with amplied electric
guitar. The JDX 48 is an active speaker-level DI that taps the natural
tone of your amplier and interfaces it with professional recording and
PA systems.

The Radial JDX 48 is easy to use, however it differs signicantly from
standard direct boxes. Like any tool, the best way to get the most out
of your JDX 48 is by understanding the design, functions and safety
features. We recommend you take a few minutes to read this manual
before operating your JDX 48.

Should you have any questions regarding the JDX 48 or it’s functions check
our FAQ at www.radialeng.com. If you would like to share your experience
with Radial products we invite you to contact us at [e-mail].

The JDX 48, one small step for mankind, one huge leap for tone fanatics!

DESIGN CONCEPT

The JDX 48 differs from a standard DI like the Radial J48. A standard DI
taps the output of the guitar before it is connected to an amplier. The JDX
48 taps the output of your amplier yielding a completely different sound.

The JDX 48 is placed between the amplier and loudspeaker. A proprietary
reactive circuit follows the constantly changing interaction between amp
and speaker to capture the dynamic response of your amp. Then an active
multi-stage lter processes the signal to emulate the frequency response
of a loudspeaker and nally, the JDX 48 uses a Class-A buffering amplier
to output a signal suitable for pro-recording and PA systems.

JDX 48 Amplier Direct Box vs. Standard Direct Box
Bass and acoustic guitars often use a standard DI to capture the clean
sound of the instrument. This works because these instruments almost
always use an unprocessed sound and the PA system merely amplies
the levels of the direct signal.

Electric guitars generally don’t use standard DIs because the amplier
and loudspeaker play an important part in a player’s sound. Typically a
microphone is used to capture the amplied guitar sound. This raises
several other variables such as bleed, placement and acoustics that come
along with using microphones.

JDX 48 Amplifier DiStAnDArD Di miXing ConSole

The Radial JDX 48 is inserted between the amplier and speaker cabinet
eliminating the microphone and delivering the sound of a player’s amp
directly to the recording or PA console. By removing the variables of a
microphone, the consistency of the sound from night to night is improved.
This is a boon to in-ear monitor users. When listening through in-ear
monitors subtle differences in mic placement and room acoustics can
translate into huge changes in tone. The JDX 48 provides great sound
while eliminating bleed from other instruments, like drums, from leaking
into the guitar mix.

Radial Engineering Ltd.

1

JDX 48 Amp Direct Box

TYPICAL APPLICATIONS

Replace a Microphone with JDX 48: The most basic use of the JDX 48

is to eliminate the need to use an open microphone to capture the sound
from the guitarist’s amp. The diagram shows the typical connection of
the JDX 48.

Using the JDX 48 with a Microphone: Mixing the signal from the JDX
48 with a microphone is a great way to create new sounds. The JDX 48
can also be mixed with a clean direct box signal for a cool effect. For
fun, try recording the JDX 48 and microphone to separate tracks that are
panned hard left and right.

Using the JDX 48 with the Radial Phazer: When the signal from the
JDX 48 and a microphone combine there will inevitably be a small time
delay between the signals. The Radial Phazer can be used to time-align
the JDX 48 signal with the microphone for fat sounds and effects.

Radial Phazer inserted
on JDX 48 channel

Radial Engineering Ltd.

2

JDX 48 Amp Direct Box

FEATURE SET

GROUND LIFT switch

eliminates hum and buzz
caused by ground loops.

300W AMP select for use with
higher wattage amps.

FROM AMP connection
for amplier output.

BASS EXT Boosts bottom
end frequencies for bass.

XLR OUTPUT mic-level,
600Ω balanced XLR out­put connects to your mix­ing console.

180° POLARITY Reverses
pin-2 and pin-3 at the XLR
output to phase align the
JDX 48 with a mic.

TO SPEAKER connects your amp to the
speaker through the JDX 48. Connec-

tion to a loudspeaker or a load box
is mandatory. Please read the safety
disclosure statement before connecting
the JDX 48.

BOOKEND DESIGN

creates a protective zone
around the jacks switches.

CABLE CLAMP

Secures cable in
place.

PSU JACK optional con­nection for the included 15
volt DC power supply.

FULL BOTTOM PAD keeps it from
sliding around and provides isolation
from electried amplier frames and
handles.

Radial Engineering Ltd.

3

JDX 48 Amp Direct Box

SIGNAL FLOW

To help you understand how the JDX 48 works take a few moments to
trace the signal ow through the block diagram.

TRANSFORMER

FROM AMP

TO SPEAKER

REACTIVE LOAD

GROUND

LIFT

ACTIVE

BANDPASS

FILTER

ACTIVE

BALANCED

DRIVER

POLARITY
REVERSE

BALANCED
XLR OUTPUT

Amplier Input and Speaker Thru-put: The FROM AMP input and TO
SPEAKER thru-put jacks are paralleled together and provides the means
to patch the JDX 48 in-between the amp output and loudspeaker.

Transformer: The transformer is the front end of the JDX 48 circuit and is
used as a reactive load that responds to the various electrical phenomena
that dictate how a particular amplier and loudspeaker sound together.
This is what makes the JDX 48 unique when compared to the “load box”
approach. A load box simply burns off the excess energy into heat and
completely ignores the amp and loudspeaker interaction. By capturing
the reactive effect between the amp and loudspeaker the JDX 48 comes
closer to the original tone than any other interface system.

The transformer also pulls double duty by electrically isolating the signal
passing through it, effectively blocking noise caused by ground loops. This
is important because the JDX 48 connects a guitar amplier to a recording
or PA system that may be powered from a different AC main circuit. Without
the transformer a ground loop may form that can cause buzz and hum.

Ground Lift: A ground lift switch is provided to further reduce noise
caused by ground loops.

Active Bandpass Filter: The analog lter section emulates the response
curve of a 4x12 speaker cabinet.

Active Balanced Driver: The output driver in the JDX 48 converts the
output to a balanced 600Ω mic-level signal for driving long cables without
signal loss or noise. This JDX 48 output can be patched into typical mi­crophone snakes and be processed along with other microphone signals.
The active balanced driver employs a discrete Class-A design for excellent
headroom and low distortion.

180° Polarity Reverse: The polarity of the JDX 48 output can be inverted
with the 180° switch. Depressing the switch will reverse the signal on pin-2
and pin-3 at the XLR output. The polarity reverse is helpful to phase align
two signals when used to interface older "pin-3 hot" equipment that does
not follow the AES standard for XLR pin-out.

Radial Engineering Ltd.

4

JDX 48 Amp Direct Box

MAKING CONNECTIONS

The JDX 48 will typically be located near the guitar amplier to facilitate
short speaker cables. We recommend speaker cables be 3m (6') or less
in length with a minimum of 16AWG two conductor cable. Longer cables
should use heavier gauges to maintain the best power transfer.

Before you begin, ensure your amplier and PA or recording system
are turned off. Lower all the volume controls to minimum to avoid
loud transients.

1. Connect your amplier’s speaker output to the FROM AMP ¼” jack
on the JDX 48.

2. Connect the SPEAKER ¼” jack on the JDX 48 to your speaker cabinet.

3. Connect the XLR output to a mic preamp input on your mixing console
using a standard XLR microphone cable up to 100m (300') in length.

4. Turn on phantom power at your mixer or preamp. If phantom power is
not available connect the JDX 48 power supply. Check the LED power
indicator to conrm power is present.

5. Turn on your amp and bring up the volume to a low level for testing.
Always test at low volume before cranking it up.

Spk CAble

Amplifier

SpeAker CAb

Radial Engineering Ltd.

Spk CAble

Xlr CAble

miXing ConSole

5

JDX 48 Amp Direct Box

USING THE JDX 48

After making connections use your amp and speaker cab as normal and
set the amp volume to an appropriate level. Keep in mind that the output
level of the JDX 48 (at the balanced XLR) will follow changes to the
amp's volume so it’s best to set your amp up the way you like it before
setting levels at the mixing console.

When your amp is setup, turn up the preamp level at the mixing console.
If you notice hum or buzz caused by ground loops, try pushing the
GROUND LIFT switch inward. This will isolate the signal ground between
your amp the mixing console and eliminate the noise.

MIXING THE JDX 48 WITH A MICROPHONE

Combining the sound of a microphone with the JDX 48 can add greater
depth and ‘fatten’ your guitar tone. The JDX 48 and microphone signals
can be mixed together to create rich textures.

After connecting the JDX 48, place a microphone on your speaker cab and
connect it to an additional mixing console channel. Set the microphone's
preamp level and start mixing the sound from both channels together.

Amplifier

miCrophone

SpeAker CAb

miXing ConSole

Try moving the microphone around the room to nd the sweet spot where
the fundamental frequencies or harmonics line up to create a satisfying
tone from the two sources. You can also send the JDX 48 signal to the left
speaker and the mic signal to the right speaker to create a stereo effect.

Radial Engineering Ltd.

6

JDX 48 Amp Direct Box

USING WITH THE RADIAL PHAZER

Combining a microphone with the JDX 48 can be very rewarding but to
really go all the way, you have to consider the problem you have created
by combining both sounds: The signal coming from the amp through
the JDX 48 is traveling at the speed of light (via electron ow), while
the corresponding sound arriving at the mic capsule via the speaker is
travelling at the speed of sound. Thus, the speaker/mic signal arrives
later than the direct JDX 48 signal due to the time it takes it to travel
through the air. This difference in phase alignment causes cancellation
at various frequencies commonly known as 'comb ltering'.

You have to now ‘correct’ the situation by aligning the two signals 'in time'
so that their fundamental frequencies are in phase. To make this all work,
you will of course need to use two channels on your mixer; one for the
mic’ed signal; and the other for the direct feed from the JDX 48. You will
also need the Radial Phazer™.

The Radial Phazer is a line level, analogue phase controller that allows
you to adjust the direct feed from the JDX 48 so that it is in phase (in time)
with the mic’ed signal. Connect the Phazer to your mixing console using
the insert point on the JDX 48's channel strip. This can be done with
balanced or unbalanced cables or using a typical insert cable with TRS
at one end, and two 1/4'” plugs at the other. (See the Radial Phazer’s
user guide for more details)

Once connected, simply turn the phase adjustment knob clockwise
slowly starting from the left until you nd the sweet spot. This will be
when the two sounds combine to create a fat rich bottom end. The
Phazer makes it easy to phase align the two signals by ear because you
can hear the tone change in real time.

JDX 48

Microphone

7

AMPLITUDE

TIME

JDX 48 and Microphone
in perfect time-alignment.

JDX 48 Amp Direct Box

AMPLITUDE

TIME

Phase off-set

Radial Engineering Ltd.

BLOCK DIAGRAM

BALANCED
XLR OUTPUT

FROM AMP

TO SPEAKER

TRANSFORMER

REACTIVE LOAD

GROUND

LIFT

ACTIVE

BANDPASS

FILTER

ACTIVE

BALANCED

DRIVER

POLARITY

REVERSE

JDX 48 SPECIFICATIONS

Audio circuit type: . . . . . . . . . . . . . . . . . . . . . . Discrete Class-A - Transformer Isolated

Frequency response: ..................................Shaped for guitar use

Dynamic range:...................................................114dB

Noise oor: ..........................................-100dBu below 0dBu

Maximum input:......................600W @ 4Ω; 300W @ 8Ω; 150W @ 16Ω

Maximum output: .......................................+14dBu (clip level)

Thermal input limit: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +49 VAC (from amplier)

Total harmonic distortion: .....................<0.015% (+10dBu input @ 1KHz)

Inter-modulation distortion: ......................0.03% (+10dBu input @ 1KHz)

Input impedance: ................................................. 15kΩ

Output impedance: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2000Ω (XLR out)

XLR conguration: .................................AES standard (pin-2 hot)

Power:.......................48V phantom or +15VDC/400mA adapter Included

Construction:........................... 14 gauge steel chassis and outer shell

Finish: ..............................................Durable powder coat

Size: ....................................5" x 6.25" x 2" (127 x 159 x 51mm)

Weight: ................................................ 2.80lbs (1.28 kg)

Warranty: .......................................Radial 3-year, transferable

Radial Engineering Ltd.

8

JDX 48 Amp Direct Box

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 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 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 [e-mail] to obtain a RA number (Return Authorization 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 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, 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.

To meet the requirements of California Proposition 65, it is our responsibility to inform you of the following:

WARNING: This product contains chemicals known to the State of California to cause
cancer, birth defects or other reproductive harm.

Please take proper care when handling and consult local government regulations before discarding.

®

www.radialeng.com

Radial Engineering Ltd.
1588 Kebet Way, Port Coquitlam BC V3C 5M5
tel: [phone] • fax: [phone]
[e-mail] • www.radialeng.com

Radial JDX 48 user guide - Part #: R870 1200 10
Appearance and specications subject to change without notice.

Copyright © 2015 Radial Engineering Ltd. all rights reserved.