-10dB CD Player
Stage
300 meters
+4dB Pro Mixer
Front of House
J-RAK™ AND J-CLAMP™
The optional J-RAK is a high density rack shelf for
Radial DI’s and splitters. It is a 2RU rack chassis that
allows up to 8 Radial devices in one 19” rackmount
package. The DI’s can be mounted with either the input
side or output side facing the front.
The optional J-CLAMP can mount a single Radial J+4
to virtually any surface. Perfect for hiding away inside
racks, on podiums or under tables.
INTRODUCTION
Congratulations
and thank you for purchasing the Radial J+4. This innovative
signal converter and line driver off ers options and performance designed for
the touring engineer, broadcaster, AV integrator and rental company that must
regularly interface consumer type audio equipment with pro-audio systems.
This manual contains all the information you need to start using the J+4 right
away. Although the J+4 is ‘plug and play’ easy to use, we suggest you read
through it and familiarize yourself with the features to get the most out of your J+4.
Should you have any questions, comments or concerns not covered in these
pages, please visit our web site and the J+4 FAQ section. This is where we post
the latest details and applications. If you do not fi nd what you need feel free to
send us an email at
and we will do our best to answer
your question as quickly as possible.
OVERVIEW
The Radial J+4 is a stereo interface designed to accept consumer level -10dB
unbalanced high impedance signals and convert them to +4dB balanced low
impedance signals for easy manipulation in professional audio environments
such as broadcast, recording studios and live touring.
Careful attention has been paid to eliminate noise by combining the advantages
of active signal buff ering with transformer isolation. The J+4 delivers 100dB
signal to noise while ensuring hum and buzz caused by ground loops along
with spurious noise from digital clocking does not pollute the signal path.
Controls include a stereo level control, high pass (low cut fi lter) and ground lift.
A selection of input connectors include a stacked set of ¼" jacks for DJ mixers
or keyboards, RCA’s for CD players and a mini 3.5mm for smartphones making
the J+4 convenient and quick to use.
As with all Radial products, the Radial J+4 is built tough to handle the most
abusive environments. A unique 14-gauge steel I-beam inner frame ensures the
sensitive PC board will not be subjected to outside stress which could potentially
cause solder joints to fail. An innovative book-end outer shell creates protective
zones around the sensitive controls, switches and connectors to further improve
dependability while a full bottom no-slip pad provides both mechanical and
electrical isolation.
BLOCK DIAGRAM
Radial Engineering Ltd.
J+4
™
User Guide
Radial Engineering Ltd.
J+4
™
User Guide
Radial Engineering Ltd.
J+4
™
User Guide
USING THE J+4
Before connecting, make sure all audio system levels are turned off to avoid any
transient popping noise that could harm your speakers. Connect the 15VDC power
supply included with the J+4. If your power supply gets lost or damaged, make sure
you replace it with an original Radial power supply as the output and polarity are
properly matched. Once the power is connected, the front panel power-on LED will
illuminate indicating the J+4 is ready to use.
Connect the desired source device (ie: a CD player, smartphone, computer sound
card, DJ mixer) to the stereo input jacks on the J+4 using a ¼" phone, RCA or 3.5mm
stereo cable. Since this part of the signal chain is unbalanced it is a good idea to
keep these cables under 8 meters (25 feet) to reduce the chance of inducted noise.
Connect the XLR outputs to your mixing console using balanced, twisted pair mic
cables. The length of the XLR cables is only limited by the quality of the cable but
typical lengths from 100 to 600 meters (300 to 2000ft) are usually not a problem.
The J+4 produces a ba4dB line-level output allowing you to bypass the
mic-preamp stage on your mixer and connect directly to a line input or even drive
a power amplifi er directly from the J+4.
If your mixer uses ¼" TRS phone jacks for balanced line inputs you can follow
the diagram below to make a TRS to XLR cable that will maintain the balanced
connection.
Tip
Ring
Sleeve
Pin-1
Pin-2
Pin-3
Female XLR
Tip
Ring
Sleeve
Shield
It is always a good idea to test the audio at low levels to make sure all your
connections are working properly. Set your audio system to a low level and the level
control on the J+4 to zero by turning the level control fully counter-clockwise. Turn
on the source device (example: CD player) and slowly turn up the level control on
the J+4. If you hear distortion, check to make sure the J+4 is not overloading the
input of your console.
Ground Lift
The J+4 is equipped with a dual ground lift switch that disconnects the pin-1 ground
connection on both XLR outputs and prevents ground loops. If you hear hum or
buzz, try toggling the recessed ‘set & forget’ ground lift switch on the side of the
J+4 using a tweaker tool.
Level Control
The LEVEL control sets the output level for both XLR
outputs. With a -10dB input signal this level control ranges
from infi nity to +10dB. The J+4 will produce a +4dB signal
level when the control is at the 12 o’clock position.
High Pass Filter
The Radial J+4 is equipped with a high-pass fi lter that is used to roll-off low
frequencies below 100Hz. Bass frequencies contain signifi cantly more energy
than higher frequencies. When playing audio tracks through a PA system, reducing
bass content with the high pass fi lter can increase the dynamic range of your audio
system. When recording a -10dB source signal, the high pass fi lter can help clean
up a muddy mix by reducing low frequencies.
APPLICATION 1: Signal level and impedance conversion
The J+4 is used to match the output from an MP3 player to the input of a pro audio
system. To get the best sound, the unbalanced -10dB signal is converted up in
level to ba4dB. The J+4 line level output allows you to connect the MP3
player to auxiliary or tape return inputs saving channel strips for microphones.
-3dB @ 100Hz
12dB/Oct
STEREO 1/8” INPUT
LEFT 1/4” INPUT
RIGHT 1/4” INPUT
LEVEL
HPF
BYPASS
HIGH PASS
FILTER
LEFT XLR
OUT
RIGHT XLR
OUT
LIFT
GND
LEFT RCA
INPUT
RIGHT RCA
INPUT
-10dB Smartphone
+4dB Pro Mixer
APPLICATION 2: Line-Driver
The J+4 is used as a signal line-driver for a -10dB consumer CD player located on
stage. The active J+4 provides signal level conversion and a buff ered balanced
output to drive the signal across long cables to a mixer or sound system without
signifi cant signal loss.
APPLICATION 3: Signal level and impedance conversion
The J+4 is used to convert signal level and balance the outputs of a satellite TV
receiver or connection to integrated audio systems in hotels, sports bars, night
clubs and restaurants.
-10dB Satellite Receivers
Commercial Audio Integration
Output Level Calibration
with -10dB input
