JL Audio RD400/4 Owner's Manual
OWNER’S MANUAL
400W 4-Channel Amplier
Thank you for purchasing a JL Audio amplifier for
your automotive sound system.
Your amplifier has been designed and manufactured to exacting
standards in order to ensure years of musical enjoyment in your vehicle.
For maximum performance, we highly recommend that you have
your new amplifier installed by an authorized JL Audio dealer. Your
authorized dealer has the training, expertise and installation equipment
to ensure optimum performance from this product. Should you
decide to install the amplifier yourself, please take the time
to read this manual thoroughly to familiarize yourself
with its installation requirements and setup procedures.
If you have any questions regarding the instructions in this
manual or any aspect of your amplifier’s operation, please contact your
authorized JL Audio dealer for assistance. If you need further assistance,
please call the JL Audio Technical Support Department
at (954) 443–1100 during business hours.
PROTECT YOUR HEARING!
We value you as a long-term customer. For
that reason, we urge you to practice restraint in
the operation of this product so as not to damage
your hearing and that of others in your vehicle.
Studies have shown that continuous exposure to
high sound pressure levels can lead to permanent
(irreparable) hearing loss. This and all other
high-power amplif iers are capable of producing
such high sound pressure levels when connected
to a speaker system. Please limit your continuous
exposure to high volume levels.
While driving, operate your audio system in
a manner that still allows you to hear necessar y
noises to operate your vehicle safely (horns,
sirens, etc.).
SERIAL NUMBER
In the event that your amplif ier requires
service or is ever stolen, you will need to have
a record of the product’s serial number. Please
take the time to enter that number in the space
provided below. The serial number can be found
on the bottom panel of the amplifier and on the
amplifier packaging.
Serial Number:
INSTALLATION APPLICATIONS
This amplifier is designed for operation in
vehicles with 12 volt, negative-ground electrical
systems. Use of this product in vehicles with
positive ground and/or voltages other than 12V
may result in damage to the product and will void
th e w arra nty.
This product is not certified or approved for
use in aircraft.
Do not attempt to “ bridge” the outputs of this
amplifier with the outputs of a second amplifier,
including an identical one.
WHAT’S INCLUDED
(1) RD400/4 amplifier
(1) Control panel cover (removable)
(1) Round logo badge
(1) 2.5 mm hex wrench
(1) User manual
Input
Voltage
(pg. 7)
4 Channel Amplifier
Left
Mono
Right
Only
+12 VDC Ground Remote
INPUT SECTION
2 | JL Audio - RD400/4 Owner’s Manual
Input Voltage
CH. 1
CH. 2
Turn-On
Mode
(pg. 6)
|
Low
High
CH. 3
CH. 4
Status
LED
(pg. 10-11)
Turn On Mode
Rem.
Input Mode
PRE-OUTS
Ch. 1 & 2
Filter Mode
|
Oset
|
2 Ch.
(L)
(R)
Selector
(pg. 8)
|
Signal
4 Ch.
Ch. 1 & 2
Input Type
(pg. 7)
Ch. 1 & 2 Input
Sensitivity Control
(pg. 7-8)
Ch. 1 & 2 Filter
Frequency
Selector
(pg. 8)
Input Type Input Sensitivity Input Sensitivity
Stereo | Mono
Filter Mode
O | HP | LP
Filter Freq. (Hz)
CHANNELS 1 & 2
CH. 1
CH. 2
(L)
Ch. 1 & 2
Clipping
Indicator
(pg. 7-8)
(R)
Clipping
Ch. 3 & 4
Input Type
(pg. 7)
Input Type
Stereo | Mono
Filter Mode
O | HP | LP
CH. 3
(L)
Ch. 3 & 4 Input
Sensitivity Control
Ch. 3 & 4
Filter Mode
Selector
(pg. 8)
Filter Freq. (Hz)
CHANNELS 3 & 4
(pg. 7-8)
CH. 4
(R)
Input
Mode
(pg. 7)
or
Clipping
Ch. 3 & 4
Clipping
Indicator
(pg. 8)
Ch. 3 & 4 Filter
Frequency
Selector
(pg. 8)
PLANNING YOUR INSTALLATION
It is important that you take the time to
read this manua l and that you plan out your
installation carefully. The following are some
considerations that you must take into account
when planning your installation.
Cooling Efficiency Considerations:
The outer shell of your JL Audio amplifier
is designed to remove heat from the amplifier
circuitry. For optimum cooling performance,
this outer shell should be exposed to the
largest possible volume of air. Enclosing the
amplifier in a small, poorly ventilated chamber
can lead to excessive heat build-up and degraded
performance. If an installation calls for an
enclosure around the amplifier, we recommend
that this enclosure be ventilated with the aid
of a fan. In normal applications, fan-cooling is
not necessary.
Mounting the amplifier upside down is
strongly discouraged. If mounting the amplifier
under a seat, make sure there is at least 1 inch
(2.5 cm) of space above the amplifier’s outer shell
to permit proper cooling.
Safety Considerations:
Your amplifier needs to be installed in a dry,
well-ventilated environment and in a manner
which does not interfere with your vehicle’s safety
equipment (air bags, seat belt systems, ABS brake
systems, etc.). You should also take the time to
securely mount the amplifier so that it does not
come loose in the event of a collision or a sudden
jolt to the vehicle.
Stupid Mistakes to Avoid:
• Check before drilling any holes in your vehicle
to make sure that you will not be drilling
through a gas tank, brake line, wiring harness or
other vital vehicle system.
• Do not run system wiring outside or underneath
the vehicle. This is an extremely dangerous
practice which can result in severe damage to
your vehicle and person.
• Protect all system wires from sharp metal edges
and wear by carefully routing them, tying
them down and using grommets and loom
where appropriate.
• Do not mount the amplifier in the engine
compartment, under the vehicle, on the roof or
in any other area that will expose the amplifier
circuitry to the elements.
Chassis Ground
Connector
(pg. 5)
+12 V Power
Connector
(pg. 5)
+12 VDC Ground Remote
Remote Turn-On
Connector
(pg. 6)
Channels 1 & 2
INPUT SECTION
Left
or
Mono
Right
Only
Input Jacks
(pg. 7)
Channels 3 & 4
CH. 1& 2 CH. 3&4
Input Jacks
(pg. 7)
Left & Right
Output Jacks
(pg. 9)
Channels 1 & 2
Speaker Outputs
(pg. 9)
(L)
CH. 1
PREOUTS
(R)
CH. 2
(L)
(R)
Channels 3 & 4
Speaker Outputs
(pg. 9)
Speaker OutputsSpeaker Outputs
CH. 3
(L)
BridgedBridged
CH. 4
(R)
3
PRODUCT DESCRIPTION
The JL Audio RD400/4 is a four-channel, fullrange audio amplifier utilizing JL Audio NexD™
ultra-high speed switching technolog y to deliver
outstanding fidelity and efficiency.
The RD400/4 can be operated with a wide
variety of source units and system configurations.
TYPICAL INSTALLATION SEQUENCE
The following represents the sequence
for a typical amplifier installation, using an
aftermarket source unit or OEM Interface
processor (like the FiX™ 82 or FiX™ 86).
Additiona l steps and different procedures may
be required in some applications. If you have any
questions, please contact your authorized
JL Audio dealer for assistance.
1) Disconnect the negative battery post
connection and secure the disconnected cable
to prevent accidental reconnection during
installation. This step is not optional.
2) Run 4 AWG copper power wire from the
battery location to the amplifier mounting
location, taking care to route it in such a
way that it will not be damaged and will
not interfere with vehicle operation. Use
4 AWG or larger copper power wire and a
fused power distribution block if additional
amplifiers are being installed with the
RD 400/4.
3) Connect the power wire to the positive battery
post. Fuse the wire with an appropriate fuse
block (and connectors) within 18 inches (45
cm) wire length of the positive battery post.
This fuse is essential to protect the vehicle.
Do not install the fuse until the power wire
has been securely connected to the amplifier.
4) Run signal cables and remote turn-on wire
from the source unit to the final amplifier
mounting location.
5) Run speaker cables from the speaker systems
to the amplifier mounting location.
6) Find a good, solid metal grounding point
close to the amplifier and connect the
negative power wire to it using appropriate
hardware (use of the JL Audio ECS master
ground lug, XB-MGLU is recommended). Use
4 AWG copper wire, no longer than 36 inches
(90 cm) from the amplifier to the ground
connection point. In some vehicles, it may
be necessary to upgrade the battery ground
wire. (See page 5 for important notice).
7) Securely mount the amplifier and
remove the top control panel cover using
the supplied 2.5 mm hex wrench.
8) Connect the positive and negative
power wires to the amplifier. A fuse
near the amplifier is not necessary if
the RD400/4 is the only device being
run from the fused main power wire.
If the fused main power wire is shared
by the RD400/4 and other amplifiers
or devices, fuse each amplifier/device
within 12 inches (30 cm) of wire length,
via a fused distribution block or multiple
individual fuse blocks/on-board fuses.
9) Connect the remote turn-on wire to the
amplifier or configure the “Turn-On Mode”
switch for automatic turn-on.
10) Connect the input cables to the amplifier.
11) Connect the spea ker cables to the amplifier.
12) Carefully review the amplifier’s control
settings to make sure that they are set
according to the needs of the system.
13) Install the power wire fuse (40A for a single
RD400/4) and reconnect the negative battery
post terminal. Install the fuse (40A) near the
amplifier (if applicable).
14) Turn on the source unit at a low level
to double-check that the amplifier is
configured correctly. Resist the temptation
to crank it up until you have verified the
control settings.
15) Make necessary adjustments to the input
sensitivity controls to obtain the right
overall output and the desired balance
in the system. See Appendix A (page 14)
for the recommended input sensitivity
setting method.
16) Replace the top control panel cover using the
supplied 2.5 mm hex wrench.
17) Enjoy the fruits of your labor with your
favorite music.
4 | JL Audio - RD400/4 Owner’s Manual
POWER CONNECTIONS
(L)
(R)
CH. 1& 2 CH. 3&4
CH. 3
(L)
CH. 4
(R)
CH. 1
(L)
CH. 2
(R)
BridgedBridged
Speaker OutputsSpeaker Outputs
PREOUTS
Before installing the amplifier, disconnect the
negative (ground) wire from the vehicle’s battery.
This will prevent accidental damage to the system,
the vehicle and your body during installation.
INPUT SECTION
Left
or
Mono
+12 VDC Ground Remote
Right
Only
The RD400/4’s “+12 V D C ” and “Ground”
connections are designed to accept 4 AWG copper
power wire. 4 AWG is the minimum copper wire
size for this amplifier.
If you are installing the RD400/4 with other
amplifiers and wish to use a single main power
wire, use 4 AWG, 2 AWG or 1/0 AWG main
power wire (depending on the overall current
demands of all the amplifiers in the system).
This 4 AWG, 2 AWG or 1/0 AWG copper power
wire should terminate into a fused distribution
block mounted as close to the amplifiers as
possible (within 12 inches / 30 cm of wire length).
The fused output of the distribution block will
connect to the RD400/4 with 4 AWG power
wire. JL Audio ECS fused distribution blocks are
recommended (XD-FDBU–2 and XD-FDBU–4).
Note: Smaller AWG numbers mean bigger wire
and vice-versa (1/0 AWG is the largest, 2 AWG is
smaller, then 4 AWG, then 8 AWG, etc.).
To connect the power wires to the amplifier,
first back out the set screw on the top of the
terminal block, using the supplied 2.5 mm hex
wrench. Strip 1/2 inch (12 mm) of insulation
from the end of each wire and insert the bare
wire into the terminal block, seating it firmly
so that no bare wire is exposed. While holding
the wire in place, tighten the set screw firmly,
taking care not to strip the head of the screw.
The ground connection should be made using
4 AWG copper wire and should be kept as short
as possible, while accessing a solid piece of sheet
metal in the vehicle. The surface of the sheet
metal should be sanded at the contact point to
create a clean, metal-to-metal connection between
the chassis and the termination of the ground
wire. For optimal grounding, we recommend
the use of a JL Audio ECS master ground lug
(XB-MGLU). Alternatively, a sheet metal screw or
bolt with a star washer can be used.
Any wires run through metal barriers (such
as firewalls), must be protected with a high
quality rubber grommet to prevent damage to the
insulation of the wire. Failure to do so may result
in a dangerous short circuit.
Only use oxygen-free copper (OFC) wire or
tinned copper wire for your amplifier’s
Power/Ground connections. Copper-clad
aluminum (CCA) wire is not recommended.
Many vehicles employ small (10 AWG - 6 AWG)
wire to ground the battery to the vehicle chassis
and to connect the alternator’s positive
connection to the battery. To prevent voltage
drops, these wires should be upgraded to 4
AWG when installing amplifier systems with
main fuse ratings above 60A.
FUSE REQUIREMENTS
It is absolutely vital that the main power
wire(s) to the amplifier(s) in the system be
fused within 18 inches (45 cm) of the positive
battery post connection. The fuse value at each
power wire should be high enough for all of the
equipment being run from that power wire. If
only the R D400/4 is being run from that power
wire, use a 40A fuse.
If fusing the amplifier near its power
connections (when more than one amp is being
run from the main power wire), use a 40A fuse
(MAXI™ big plastic-body fuse is recommended).
5
TURNON OPTIONS
(L)
(R)
CH. 1& 2 CH. 3&4
CH. 3
(L)
CH. 4
(R)
CH. 1
(L)
CH. 2
(R)
BridgedBridged
Speaker OutputsSpeaker Outputs
PREOUTS
The RD400/4 can be switched on and off using
one of three methods, determined by the position
of the amplifier’s “Turn-On Mode” switch. Please
read these options and decide which is best suited
for your specific system.
1) +12V remote turn-on lead
2) DC offset-sensing turn-on circuit
3) Signa l-sensing turn-on circuit
+12V Remote Turn-On: This is the preferred
method for turning the amplif ier on/off. The
amplifier will turn on when +12V is present at
its “Remote” input and turn off when +12V is
switched off. This +12V remote turn-on signal
is typically controlled by a source unit or OEM
interface processor’s remote turn-on wire. The
RD4 0 0/4’s “Remote” turn-on connector will
accept 18 AWG – 12 AWG wire. To connect
the remote turn-on wire to the amplifier, first
back out the set screw on the top of the terminal
block, using the supplied 2.5 mm hex wrench.
Strip 1/2 inch (12 mm) of wire and insert the
bare wire into the terminal block, seating it
firmly so that no bare wire is exposed. While
holding the wire in the terminal, tighten the
set screw firmly, taking care not to strip the
head of the screw and making sure that the
wire is firmly gripped by the set screw.
INPUT SECTION
Left
or
Mono
+12 VDC Ground Remote
Right
Only
These methods are useful when a conventional
+12V remote turn-on signal is not available in a
system. These allow you to operate the amplifier
without having to locate a remote turn-on lead at
the source unit, which can be very useful when
interfacing the amplifier with OEM (factory)
audio systems that do not use conventional +12V
turn-on leads.
Depending on the characteristics of the audio
signal, one of the following methods may work
better than the other. We recommend trying DC
Offset-Sensing first as it does not require a long
delay to turn the system off after the signal is
shut off.
DC Offset-Sensing: The amplifier will turn on
and off by detecting the presence of a very small
DC signal (offset) that is typical in the audio
output of most OEM (factory) source units and
amplifiers. The amplifier will turn on and off in
reaction to the presence or absence of this DC
Offset. The sensitivity of this circuit is designed
for high-level (speaker level) signals, not for lowlevel (preamp level) signals. The circuit senses
the input signal from CH. 1 only.
Signal-Sensing: The amplif ier will turn on
and off by detecting the presence of a full-range
audio signal. After approximately 30 seconds,
the amplifier will shut off. The sensitivity of this
circuit is designed for high-level (speaker level)
signals, not for low-level (preamp level) signals.
The circuit is tuned to react to signa ls at midrange frequencies. This prevents false switching
from signals created by moving loudspeakers
that are in parallel with the amplifier’s input
signal. The circuit senses the input signal from
CH. 1 only.
If a source unit does not have a dedicated
remote turn-on output, consider one of the
following alternative turn-on options:
6 | JL Audio - RD400/4 Owner’s Manual
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