JL Audio Car Stereo System HD600 4 User Manual

owner’s manual  
4-Channel Class-D Full-Range Amplifier  
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 so as 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.  
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ProteCt Your Hearing!  
installation aPPliCations  
Cooling efficiency Considerations:  
Your JL Audio amplifier employs an  
safety Considerations:  
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 amplifiers are capable of producing  
such high sound pressure levels when connected  
to a speaker system. Please limit your continuous  
exposure to high volume levels.  
This amplifier is designed for operation in  
vehicles with 12V, 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  
the warranty.  
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.  
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 using appropriate  
hardware so that it does not come loose in the  
event of a collision or a sudden jolt to the vehicle.  
advanced type of heat management, called  
RealSink™. This feature takes advantage of  
convection and radiation effects to remove  
heat from the amplifier circuitry. For optimum  
cooling performance, the vertical heat sinks  
located at the sides of the amplifier should be  
exposed to as large a volume of air as possible.  
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.  
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.  
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.  
While driving, operate your audio system in  
a manner that still allows you to hear necessary  
noises to operate your vehicle safely (horns,  
sirens, etc.).  
Planning Your installation  
It is important that you take the time to read  
this manual and that you plan out your  
installation carefully. The following are some  
considerations that you must take into account  
when planning your installation.  
serial number  
In the event that your amplifier 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:  
Power Status  
Indicator  
(pg. 16)  
Filter Slope  
Selection  
(pg. 11)  
Input Sensitivity  
Control  
Input Mode  
Selection  
(pg. 9)  
Preouts From  
Selection  
(pg. 13)  
Input Sensitivity  
Control  
(pg. 10)  
Filter Slope  
Selection  
(pg. 11)  
(pg. 10)  
Remote Level  
Filter Mode  
Selection  
(pg. 11)  
Filter Mode  
Selection  
(pg. 11)  
Filter Frequency  
Selector  
(pg. 11)  
Input Voltage  
Selection  
(pg. 10)  
Control  
Selection  
(pg. 13)  
Input Voltage  
Selection  
(pg. 10)  
Filter Frequency  
Selector  
(pg. 11)  
Chassis Ground  
Connector  
Front Left & Right  
Channel Input Jacks  
(pg. 9)  
Left & Right Preamp  
Front  
Speaker Outputs  
(pgs. 14-15)  
Rear  
Speaker Outputs  
(pgs. 14-15)  
Output Jacks  
(pg. 13)  
(pgs. 6-7)  
Jack for  
Remote Level  
Control Knob  
(pg. 13)  
+12 V Power  
Remote Turn-On  
Connector  
Rear Left & Right  
Channel Input Jacks  
(pg. 9)  
Connector  
(pgs. 6-7)  
(pgs. 6-7)  
L
+12 VDC Ground Remote  
L
Front  
Inputs  
R
Rear  
Preouts  
R
Remote  
Level  
Control  
2 | JL Audio - HD600/4 Owner’s Manual  
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ProduCt desCriPtion  
tYPiCal installation sequenCe  
The following represents the sequence for  
a typical amplifier installation, using an  
aftermarket source unit or OEM Interface  
processor (like the CleanSweep® CL441dsp).  
Additional steps and different procedures may  
be required in some applications. If you have  
any questions, please contact your authorized  
JL Audio dealer for assistance.  
The JL Audio HD600/4 is a very powerful  
and compact four-channel, full-range amplifier  
utilizing patented Single Cycle Control™  
Class D technology for all channels. This  
groundbreaking technology delivers reference-  
grade sonic performance while requiring  
far less current from the vehicle’s electrical  
system than a conventional amplifier.  
JL Audio’s exclusive R.I.P.S. power supply  
design optimizes the output of each channel pair  
for any impedance between 1.5 and 4 ohms per  
channel (3-8 ohms bridged) allowing you to get  
full use of the HD600/4’s performance capabilities  
with a wide range of speaker systems.  
The tightly regulated power supply design also  
means that the HD600/4’s clean power output  
capability remains stable over a wide range of  
vehicle voltages, resulting in enhanced fidelity.  
The HD600/4 flexible, studio-grade signal  
processing allows it to be deployed in a wide  
range of system applications:  
5) As a very powerful (300W x 2) two-channel  
satellite amplifier in a bi-amplified system,  
delivering high-passed signals to a stereo  
speaker system. Preamp outputs permit  
connection of a separate amplifier to drive the  
subwoofer system.  
7) Securely mount the amplifier using  
appropriate hardware. (See page 8 for detailed  
mounting instructions).  
8) Connect the remote turn-on wire and the  
positive and negative power wires to the  
amplifier’s power connector plug. Then insert  
the power connector plug into the amplifier’s  
power connector receptacle, pushing firmly.  
9) Connect the RCA input cables  
6) As a powerful (300W x 2) two-channel  
subwoofer amplifier in a bi-amplified system,  
delivering low-passed signals to a dual  
subwoofer system. Preamp outputs permit  
connection of a separate amplifier to drive the  
satellite speakers.  
1) Disconnect the negative battery post  
connection and secure the disconnected cable  
to prevent accidental re-connection during  
installation. This step is not optional!  
2) Run 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. 4 AWG is recommended  
for wire runs greater than 72 inches (180  
cm) in length. Use of 8 AWG power wire is  
acceptable for shorter runs, such as from a  
power distribution block to the amplifier or  
from a trunk-mounted battery. Use a 2 AWG  
or 1/0 AWG main power wire with a power  
distribution block when additional amplifiers  
are being installed with the HD600/4 and  
powered from the same main power wire.  
3) Connect 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 connected to the amplifier.  
to the amplifier.  
10) Connect the speaker wires to the speaker  
connector plugs and insert the plugs firmly  
into the speaker connector receptacles.  
11) Carefully review the amplifier’s control  
settings to make sure that they are set  
according to the needs of the system.  
12) Install power wire fuse (50A for a  
single HD600/4) and reconnect the negative  
battery post terminal.  
13) 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.  
14) Make necessary adjustments to the input  
sensitivity controls to obtain the right  
overall output and the desired balance  
in the system. See Appendix C (pages 18, 19)  
for the recommended input sensitivity  
setting method.  
The HD600/4’s flexible input and crossover  
sections permit operation with a wide variety of  
source units and system configurations. It can be  
operated with a single pair of stereo inputs or with  
separate inputs for its front and rear channels.  
The HD600/4’s preamp output can send pass-  
through signals from the Front Inputs only or it  
can sum all four input channels to feed a non-  
fading signal to a separate subwoofer amplifier.  
1) As a four-channel (150W x 4) full-range  
amplifier, delivering full-range signals to two  
separate stereo speaker systems (front and rear,  
for example).  
As we said, it’s very flexible.  
2) As a powerful (150W x 4) four-channel satellite  
amplifier in a bi-amplified system, delivering  
high-passed signals to front and rear speaker  
systems. Preamp outputs permit connection of a  
separate amplifier to drive the subwoofer system.  
15) Enjoy the fruits of your labor with your  
favorite music.  
3) As a 600W full-system amplifier in  
bi-amplified mode with one channel pair  
driving subwoofers in low-pass mode (150W  
x 2 or 300W x 1) and the other channel pair  
driving main speakers in high-pass mode  
(150W x 2).  
4) Run signal cables (RCA cables) and remote  
turn-on wire from the source unit or interface  
processor to the amplifier mounting location.  
5) Run speaker wire from the speaker systems to  
the amplifier mounting location.  
6) Find a good, solid, bare metal grounding  
point close to the amplifier and connect the  
negative power wire to it using appropriate  
hardware. Use minimum 8 AWG power wire,  
no longer than 36 inches (90 cm) or 4 AWG  
wire up to 60 inches (150 cm) long from the  
amplifier to the ground connection point. In  
some vehicles, it may be necessary to upgrade  
the battery’s ground wire as well. (See page 7  
for important notice).  
4) As a very powerful (300W x 2) full-range  
amplifier, delivering full-range signals to a  
stereo speaker system.  
4 | JL Audio - HD600/4 Owner’s Manual  
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Power and turn-on ConneCtions  
ground Connection  
The HD600/4’s “Remote” turn-on connector  
is designed to accept 18 AWG – 12 AWG wire. 18  
AWG is more than adequate for this purpose.  
To connect the remote turn-on wire to the  
amplifier, first back out the set screw on the  
bottom of the Power Connector Plug, using the  
supplied hex wrench. Strip 1/2 inch (12mm) of  
wire and insert the bare wire into the receptacle,  
seating it firmly so that no bare wire is exposed.  
When using smaller wire, it may be necessary to  
strip 1 inch of insulation from the wire and fold  
the bare wire in half prior to insertion. While  
holding the wire in the terminal, tighten the  
set screw firmly using the supplied 2.5 mm hex  
wrench, taking care not to strip the head of the  
screw and making sure that the wire is firmly  
gripped by the set screw.  
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.  
We do not recommend the use of “copper-  
clad aluminum wire” or “CCA” wire because  
this wire is significantly less conductive than  
pure copper wire. Only use pure copper power  
wire, such as JL Audio’s MetaWire™. Tinned  
copper wire (silver color) is acceptable as the  
tin-plating is only a very minor component of  
the wire.  
The chassis ground connection must be  
made using 4 AWG or 8 AWG pure 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 with a brass or copper power ring. For  
optimal grounding, we recommend the  
use of a JL Audio ECS master ground lug  
(XB-MGLU). Alternatively, a sheet metal  
screw or bolt can be used with a star washer.  
+12 VDC Ground Remote  
Front  
Fuse requirements  
The installation of a fuse on the main power  
wire, within 18 wire inches (45 cm) of the positive  
battery terminal is vital to protect the wire and  
the vehicle from fire in the event of a collision  
or short-circuit. The fuse value at each power  
wire should be just high enough for all of the  
equipment being run from that power wire. Do  
not use a fuse with a value that far exceeds the  
total fuse rating of the electronics connected to  
the wire.  
If only the HD600/4 is being run from that  
power wire, we recommend a 50A fuse be used.  
AGU (big glass fuse). AFS (small blade fuse)  
or MaxiFuse™ (big plastic-body fuse) types are  
recommended. If other amplifiers are also being  
powered from the wire and exceed 80 amps in  
total fuse rating, we recommend the use of an  
ANL (large-blade) fuse and holder. Please consult  
with your JL Audio dealer to make sure that the  
wire, fuse holder and fuse rating you have selected  
are appropriate for your system’s needs.  
If other amplifiers are also being powered from  
a main power wire and exceed 80 amps in total  
fuse rating, we recommend the use of an ANL  
(large-blade) fuse and holder. Each amplifier can  
then be fused independently at the outputs of  
the power distribution block. Use JL Audio part  
XC-FOA-2PAK and appropriate MaxiFuse™ type  
fuses with JL Audio distribution blocks.  
Please consult with your JL Audio  
+12V battery Connection  
You will need to connect a power wire to  
the vehicle’s positive battery terminal, using an  
appropriate power ring or specialized battery  
terminal connector, such as the JL Audio  
XB-BTU. This connection must be tight and  
corrosion-free to ensure proper connectivity. This  
wire MUST be fused appropriately for safety. Any  
positive power wires run through metal barriers  
(such as firewalls), must be protected with a high  
quality insulating grommet to prevent damage to  
the insulation of the wire. Failure to do so may  
result in a dangerous short circuit.  
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 pure copper wire when installing amplifier  
systems with main fuse ratings above 60A.  
amplifier Power Connector Plug  
To connect the power wires and the remote  
turn-on wire to the amplifier, unplug the power  
connector plug from the amplifier chassis (pull  
back firmly) and back out the set screws on  
the connector plug, using the supplied 4 mm  
hex wrench for the +12 VDC” and “Ground”  
connections and the supplied 2.5 mm hex wrench  
for the “Remote” connection. Strip 3/8 inch (10  
mm) of insulation from the end of each wire and  
insert the bare wire into the receptacle on power  
connector plug, seating it firmly so that no bare  
wire is exposed. While holding each wire in place,  
tighten each set screw firmly, taking care not to  
strip the head of the screw.  
turn-on wire  
The HD600/4 uses a conventional +12V remote  
turn-on wire, typically controlled by the source  
unit’s remote turn-on output. The amplifier will  
turn on when +12V is present at its “Remote”  
input and turn off when +12V is switched off. If  
a source unit does not have a dedicated remote  
turn-on output, the amplifier’s turn-on lead can  
be connected to +12V via a switch that derives  
power from an ignition-switched circuit.  
Power wire requirements  
The HD600/4’s “+12 VDC” and “Ground”  
connections are designed to accept 4 AWG power  
wire. 4 AWG pure copper wire is recommended  
for any power wire run longer than 72 inches (180  
cm). For runs shorter than 72 inches, 8 AWG pure  
copper power wire is acceptable.  
If you are installing the HD600/4 with other  
amplifiers and wish to use a single main power  
wire, use 2 AWG or 1/0 AWG pure copper wire  
as a main power wire. This 2 AWG or 1/0 AWG  
power wire should terminate into a distribution  
block mounted as close to the amplifiers as  
possible and should connect to the HD600/4 with  
4 AWG or 8 AWG pure copper power wire.  
Please note that lower 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.).  
dealer to make sure that the wire, fuse  
holder and fuse ratings are appropriate  
for your system’s needs. The safety of  
your installation depends on appropriate  
power connections and fuse protection.  
Never make power connections with a “live”  
wire. Always disconnect the negative battery  
post before making any connections or  
adjustments to a 12V power connection!  
6 | JL Audio - HD600/4 Owner’s Manual  
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amPliFier mounting oPtions  
The HD600/4 has two mounting options to  
ease in installation.  
Control Panel seCuritY CoVer  
amPliFier inPuts  
CHannel Control seCtions  
The HD600/4 features a Control Panel Security  
Cover. When installed, the cover ensures that  
your amplifier settings are not accidentally  
changed while creating a clean aesthetic for the  
amplifier and your installation. The control panel  
security cover is pre-installed at the factory and  
must be temporarily removed for access to the  
controls described throughout this manual.  
The HD600/4 has two separate input sections,  
one for the “Front” left and right channels and  
another for the “Rear” left and right channels.  
Each section consists of a pair of RCA-type input  
jacks on the Connection Panel of the amplifier  
and a pair of input controls on the Control Panel  
of the amplifier: an “Input Voltage” switch and an  
Input Sens.” rotary control.  
Flanking the “General Setup” section  
on the Control Panel of the amplifer are  
two sets of identical controls: one for the  
“Rear Channel Controls” (on the left side)  
and one for the “Front Channel Controls”  
of the amplifier (on the right side).  
In each of these sections you will find an  
“Input Voltage” range switch and a rotary  
control labeled “Input Sens.” (Input Sensitivity).  
These controls are designed to match the input  
sensitivity of the HD600/4 to the specific signal  
source that is feeding it and must be adjusted,  
with care, following the procedures outlined in  
this manual. Failure to make correct adjustments  
can result in weak output, excessive distortion  
and/or undesirable noise in the audio output of  
the amplifier!  
standard mounting  
The security cover is secured by a single 2.5  
mm hex-head screw at the far right of the panel.  
Loosen the hex-head screw to release the security  
cover (it is not necessary to completely remove the  
screw). To re-install the security cover once all  
adjustments have been made, insert the tongue on  
the cover’s left edge into the groove where the left-  
side heatsink meets the control panel, hinge the  
panel closed and secure the screw using the  
supplied 2.5 mm hex wrench. Do not overtighten  
the screw.  
mote  
L
Front  
Inputs  
Rear  
P
The standard method of mounting requires  
removal of the four corner caps with the 3/16-inch  
hex wrench included with your amplifier. Using  
appropriate mounting screws (not included),  
secure the amplifier in all four corners and  
replace the corner caps.  
R
inPut mode” switCH  
The Control Panel houses an “Input  
Mode” switch located under the “General Setup”  
heading. This switch allows operation of all four  
amplifier channels with only one pair of input  
signals or with independent front and rear input  
signal pairs.  
Note: The Channel Control sections also house  
“Filter Mode”, “Filter Slope” and “Filter Freq.”  
controls. These are crossover filter controls  
and will be discussed in the next section of this  
manual. This section will explain the Input  
Controls only.  
lateral mounting Feet  
Lateral Mounting Feet are also included with  
your HD600/4 to provide an alternative mounting  
option. Each mounting foot should be attached  
to the bottom of the amplifier by screwing the  
provided bolt into the bottom of the amplifier and  
up into the corner cap with the supplied 1/8-inch  
hex wrench. Next, using appropriate mounting  
screws (not included), secure the amplifier by its  
four Lateral Mounting Feet.  
To use separate inputs for the “Front” and  
“Rear” amplifier sections, (in order to permit  
front-to-rear fading, for example), select “4 Ch.”  
on the “Input Mode” switch. In this mode, you  
must connect separate pairs of input cables to the  
“Front” and “Rear” amplifier inputs.  
To operate all four channels of the HD600/4  
with a single pair of stereo inputs, select the  
“2 Ch.” position on the “Input Mode”  
switch and connect a single pair of input  
cables to the “Front” input jacks only. In  
this mode, the amplifier will route the  
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.  
signals connected to the “Front” inputs to  
the Front and Rear amplifier channels.  
8 | JL Audio - HD600/4 Owner’s Manual  
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input Voltage” switch  
input sens.” Control  
CrossoVer Controls  
A wide range of signal input voltages can  
be accommodated by each of the HD600/4’s  
differential-balanced inputs (200mV – 8V RMS).  
This wide range is split up into two sub-ranges,  
accessible via the “Input Voltage” switches located  
in each input section of the amplifier. Be aware  
that each input section’s “Input Voltage” switch  
will have to be configured, regardless of how many  
input cables are actually feeding the amplifier.  
The “Low” position on each “Input  
Voltage” switch selects an input sensitivity  
range between 200mV and 2V. This means that  
the “Input Sens.” rotary control will operate  
within that voltage window. If you are using  
an aftermarket source unit, with preamp-level  
outputs, this is most likely the position that  
you will use (regardless of what voltage output  
capability is claimed by the source unit).  
The “High” position on each “Input Voltage”  
switch selects an input sensitivity range between  
800mV and 8V. This is for use with speaker-level  
outputs from source units and small amplifiers  
found in many OEM (factory-installed) systems.  
To use speaker-level sources, splice the speaker  
output wires of the source unit or small amplifier  
onto a pair of RCA plugs for each input pair  
or use the JL Audio ECS Speaker Wire to RCA  
adaptor (XB-CLRAIC2-SW).  
Located next to the “Input Voltage” switch  
in each input section is a rotary control labeled  
“Input Sens.”. Once the appropriate “Input  
Voltage” range has been selected, this control  
can be used to match the source unit’s output  
voltage to the input stage of each pair of amplifier  
channels for maximum clean output. Rotating the  
control clockwise will result in higher sensitivity  
(louder for a given input voltage). Rotating the  
control counter-clockwise will result in lower  
sensitivity (quieter for a given input voltage). To  
properly set each pair of amplifier channels for  
maximum clean output, please refer to Appendix  
C (pages 18, 19) in this manual.  
After using this procedure, you can then adjust  
the relative level of each channel pair by adjusting  
the input sensitivity downward on either or both  
channel pairs, if they require attenuation to  
achieve the desired system balance.  
Do not increase the “Input Sens.” setting for  
any amplifier in the system beyond the maximum  
level established during the procedure outlined in  
Appendix C (pages 18, 19). Doing so will result in  
audible distortion and possible speaker damage.  
Be aware that both “Input Sens.” adjustments  
will have to be made, regardless of how many  
input cables are feeding the amplifier. These  
controls will allow you to set the appropriate  
relative levels for the “Front” channels relative  
to the “Rear” channels and any other amplifier  
channels in the system.  
Crossovers are groups of electronic filters  
designed to control the frequency ranges  
that each speaker in a system will be tasked  
with reproducing. Proper crossover setup is  
critical to sound quality and reliability.  
The HD600/4 has two individual filters,  
one for the “Front” channels and the  
other for the “Rear” channels. Each can be  
configured as a high-pass filter (attenuates low  
frequencies) or as a low-pass filter (attenuates  
high frequencies). Additionally, the user can  
select from a shallow (12dB/octave) filter slope  
or a more aggressive (24dB/octave) slope.  
Each Channel Control section contains  
identical crossover filter controls.  
2) “Filter Slope” Control: This switch allows you  
to select from two filter slopes.  
“ 12dB”: Configures the filter to attenuate  
frequencies above or below the selected  
filter frequency at a rate of 12 dB per octave  
(Butterworth alignment).  
“ 24dB”: Configures the filter to attenuate  
frequencies above or below the selected  
filter frequency at a rate of 24 dB per octave  
(Linkwitz-Riley alignment).  
Depending on the speaker system and the  
vehicle, different filter slopes may be required to  
produce a smooth transition between the sound  
of different speakers in the system.  
In high-pass mode, the sharper “24dB” setting  
will do a better job of protecting small speakers  
with limited power handling. In low-pass  
mode, the “24dB” setting can also help by more  
aggressively removing lower midrange output  
from a subwoofer system.  
The shallower “12dB” octave setting  
allows for more output overlap between  
the speakers being crossed over. In many  
cases, this will result in a smoother “blend”  
or transition between speaker systems.  
Experiment to find the slope or combination  
of slopes which best matches the acoustic  
requirements of your system.  
1) “Filter Mode” Control: this switch allows you  
to configure the filter for that Channel Pair  
into one of two filter types.  
“Off”: Defeats the filter completely, allowing  
the full range of frequencies present at the  
inputs to feed that pair of channels. This  
is useful for systems utilizing outboard  
crossovers or requiring full-range reproduction  
from that pair of channels.  
The output of the amplifier decreases for a  
given input voltage when the “Input Range”  
switch is placed in the “High” position. The  
output increases with the switch in the “Low”  
position. While this may sound counter-  
intuitive, it is correct as described.  
3) “Filter Freq. (Hz)” Control:  
This control selects the frequency at which the  
filter begins to attenuate the signal and refers  
specifically to the frequency at which output  
has been attenuated by -3dB.  
“HP” (High-Pass): Configures the  
CH 1&2 filter to attenuate frequencies  
below the selected filter frequency.  
Useful for connection of component  
speakers in a bi-amplified system.  
The filter frequency markings surrounding this  
rotary control are for reference purposes and are  
generally accurate to within 1/3 octave or better. If  
you would like to select the filter cutoff frequency  
with a higher level of precision, consult the charts  
in Appendix B (page 18) of this manual.  
“LP” (Low-Pass): Attenuates frequencies  
above the selected filter frequency.  
Useful for connection of subwoofer(s)  
in a bi-amplified system.  
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bi-amPliFied sYstems  
bi-amplified system with one  
PreamP outPuts  
Bi-amplified systems are defined as systems  
in which separate amplifier channels drive low-  
frequency (LF) and high-frequency (HF) speakers  
and are separately filtered to send appropriate  
frequency ranges to each speaker system.  
The most common application of  
bi-amplification in mobile audio is to drive a  
subwoofer system from one or more amplifiers or  
channels and component speakers from separate  
amplifiers or channels.  
Hd600/4 in four-channel mode and  
a separate subwoofer amplifier  
This configuration requires that the  
separate subwoofer amplifier has a built-in  
low-pass filter. In this configuration, the  
“Front” channels of the HD600/4 will drive  
front component speakers (stereo 150W x 2)  
with high-pass filtering. The “Rear” channels  
will drive rear component speakers in stereo  
(150W x 2) with high-pass filtering.  
The HD600/4 incorporates a pass-through  
preamp output section, so that additional  
amplifiers can easily be connected to the same  
signal(s) feeding the HD600/4. These preamp  
output signals are accessible via a stereo pair  
of RCA-type jacks, labeled “Preouts”, on the  
Connection Panel.  
3) “F+R” (Front + Rear): This mode delivers a  
sum of the signals being fed to the “Front  
Inputs” and the “Rear Inputs” of the  
amplifier. When the HD600/4 is being used  
to drive front and rear speaker systems, this  
preamp output mode will deliver a summed  
front/rear signal to the subwoofer amplifier,  
while permitting fading of the front and rear  
speaker systems from the source unit.  
L
The HD600/4 can be configured to drive a  
bi-amplified system by itself or with a separate  
subwoofer amplifier.  
The separate subwoofer amplifier will drive the  
subwoofer system with low-pass filtering (select a  
filter frequency of 80-90 Hz to start). The inputs  
of the subwoofer amplifier can be fed from the  
HD600/4’s preamp output or from a dedicated  
subwoofer output on the source unit.  
remote leVel Control (oPtional)  
With the addition of the optional Remote Level  
Control (HD-RLC), you can control the volume  
of one or both channel pairs of the HD600/4  
from the front of the vehicle. This is useful for  
subwoofer level control or even as a master  
volume control for the system.  
The HD-RLC connects to the jack labeled  
“Remote Level Control” on the Connection  
Panel of the amplifier using a standard telephone  
cable (supplied with the HD-RLC).  
Preouts  
Remot  
Level  
Contro  
R
bi-amplified system with one Hd600/4  
In this configuration, the “Rear” channels  
of the HD600/4 will drive subwoofers  
(stereo 150W x 2 or bridged 300W x 1) with  
low-pass filtering. The “Front” channels  
will drive component speakers in stereo  
(150W x 2) with high-pass filtering.  
Crossover Setup for Bi-Amplified System with one  
HD600/4 and a separate subwoofer amplifier:  
Once the input and preamp output sections  
have been configured appropriately, go to the  
“Front Channel Controls” Section. Select “HP”  
(high-pass) on the “Filter Mode” switch and  
“12dB” or “24dB” on the “Filter Slope” switch  
and an appropriate “Filter Freq.” (80-90 Hz is a  
good starting point).  
The term “pass-through” refers to the fact that  
the Preamp Output signals are not affected by any  
crossover filter or input sensitivity setting selected  
on the HD600/4 (if the input signal is full-range,  
the Preamp Output will be full-range). These  
preamp output signals are buffered to prevent  
noise and are always preamp level, regardless of  
the level of signals feeding the HD600/4’s inputs.  
The pass-through Preamp Outputs can be  
configured two different ways using the switch  
labeled “Preouts From” in the “General Setup”  
section of the Control Panel.  
If desired, multiple HD amplifiers can be  
controlled from a single HD-RLC controller  
using a simple phone line “splitter” and multiple  
phone cables.  
Crossover Setup for Bi-Amplified System  
with one HD600/4:  
Once the input sections have been configured  
appropriately, go to the “Rear Channel Controls”  
Section. Select “LP” (low-pass) on the “Filter  
Mode” switch and “12dB” or “24dB” on the  
“Filter Slope” switch and an appropriate “Filter  
Freq.” (80-90 Hz is a good starting point).  
Next, turn your attention to the “Front  
Channel Controls” Section. and select “HP”  
(high-pass) on the “Filter Mode” switch and  
“12dB” or “24dB” on the “Filter Slope”  
switch and an appropriate “Filter Freq.”  
(again, 80-90 Hz is a good starting point).  
After proper adjustment of the Front and  
Rear channel “Input Range” and “Input  
Sens.” controls using the method shown  
in Appendix C (pages 18, 19), you can  
Next, turn your attention to the “Rear  
Channel Controls” Section and select “HP”  
(high-pass) on the “Filter Mode” switch and  
“12dB” or “24dB” on the “Filter Slope” switch  
and an appropriate “Filter Freq.” (again, 80-90 Hz  
is a good starting point).  
After proper adjustment of the HD600/4’s and  
the subwoofer amplifier’s “Input Range” and  
“Input Sens.”, you can fine tune filter frequencies  
and slopes and attenuate either pair of channels  
to achieve proper balance. For proper adjustment  
of the “Input Sens.” controls of the HD600/4 use  
the method shown in Appendix C (pages 18, 19).  
For precise filter frequency information for the  
HD600/4 refer to Appendix B (pages 18). Refer to  
the subwoofer amplifier owner’s manual for its  
proper adjustment levels.  
L
Preouts  
Remote  
Level  
Control  
R
When connected to the amplifier, the HD-RLC  
operates as follows. At full counter-clockwise  
rotation, the audio will mute completely. At full  
clockwise rotation the level will be the same as if  
the HD-RLC was not connected at all. In other  
words, it operates strictly as a level attenuator.  
Depending on the application, you may want  
the HD-RLC to only affect one channel pair or  
both channel pairs. A switch labeled “Remote  
Level Control” in the “General Setup” Section  
of the Control Panel allows you to determine  
whether the HD-RLC affects the level of all  
channels All Ch.” or only the rear channels  
“Rear Ch.”  
1) “Front”: The preamp output delivers the same  
signal that is connected to the HD600/4’s  
“Front Inputs”. This mode is useful for  
feeding a subwoofer amplifier when the  
HD600/4 is being used to drive front and rear  
speaker systems. In this mode, the preamp  
output level will track with the signal level  
of the front input signals, allowing the user  
to fade the rear channels in and out, without  
affecting the subwoofer level.  
fine tune filter frequencies and slopes and  
attenuate either pair of channels to achieve  
proper balance. For precise filter frequency  
information refer to Appendix B (page 18).  
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The RBC-1 Remote Bass Control used with  
JL Audio Slash, Slash v2, e-Series, A-Series and  
G-Series amplifiers is NOT compatible with the  
HD Series amplifiers. If you attempt to connect  
an RBC-1 to an HD amplifer, the control will  
not work. You must use the HD-RLC controller.  
If you connect a load higher than 4Ω nominal  
per channel in stereo mode (or 8Ω in bridged  
mode), power will drop by half with every  
doubling of impedance above 4Ω stereo / 8Ω  
mono. If you connect a load lower than 1.5Ω  
nominal per channel in stereo mode (or 3Ω in  
bridged mode, the amplifier protection  
circuitry activates a “safe” mode which reduces  
amplifier power to protect the circuitry from  
failure (the LED status indicator on the control  
panel will light up amber to indicate that this  
has happened). See page 16 for details.  
To bridge a pair of channels, use the “Left +”  
and “Right –” speaker connectors only  
(the “Left –” and “Right +” remain unused).  
Then connect a mono signal to both left and  
right RCA inputs for that channel pair. This  
requires an RCA “Y-Adaptor” (sold separately),  
because a bridged pair of channels requires that  
both amplifier channels of the bridged pair  
receive input. Connection of only one RCA input  
will result in reduced power output, increased  
distortion and can cause the amplifier to overheat.  
When bridged, each channel pair will  
For example, if you are using the HD600/4 in a  
stand-alone bi-amplified mode, you may want the  
HD-RLC to only affect the level of the subwoofer  
channels. Setting the “Remote Level Control”  
switch to the “Rear Ch.” position accomplishes  
this (provided the subwoofer system is connected  
to the rear channels).  
In other cases, you may want control of all  
four channels at the same time, so you would  
set the “Remote Level Control” switch to the  
All Ch.” position.  
sPeaker outPuts  
The HD600/4 employs JL Audio’s exclusive  
Regulated, Intelligent Power Supply (R.I.P.S.)  
design. The operation of the R.I.P.S. system is  
independent for each pair of channels. This  
sophisticated power supply allows the amplifier to  
produce its optimum power (150 watts x 4) over a  
wide range of speaker impedances.  
deliver optimum power into a 3-8Ω load.  
Operating bridged channel pairs into a load  
lower than 3Ω is not recommended.  
Speaker loads below 1.5Ω nominal per channel  
in stereo or 3Ω nominal in bridged mode are  
not recommended and may cause the amplifier  
output to distort excessively.  
speaker Connector Plugs  
To connect the speaker wires to the amplifier,  
unplug the speaker connector plugs from the  
amplifier chassis (pull back firmly) and back out  
the set screws on each connector plug, using the  
supplied 2.0 mm hex wrench. Strip 3/8 inch (10  
mm) of insulation from the end of each wire and  
insert the bare wire into the receptacle on the  
speaker connector plug, seating it firmly so that  
no bare wire is exposed. While holding each wire  
in place, tighten each set screw firmly, taking care  
not to strip the head of the screw.  
bridging Considerations  
Bridging is the practice of combining the  
output of two amplifier channels to drive a single  
load. When bridged, each channel produces  
signals of equal magnitude, but opposite polarity.  
The combined output of the two channels  
provides twice the output voltage available from a  
single channel. The HD600/4 has been designed  
for bridging of its channel pairs without the need  
for input inversion adaptors.  
Unlike conventional amplifiers that require  
a specific impedance to produce optimum  
power, the R.I.P.S.-equipped HD600/4 gives  
you the freedom to use a variety of speaker  
configurations that achieve final nominal  
impedances between 1.5 – 4Ω per channel in  
stereo (without sacrificing power output or sound  
quality). When bridged, each channel pair will  
optimize output at 300 watts between 3 – 8Ω.  
The operation of the R.I.P.S. circuitry is  
entirely automatic and adjusts itself every time the  
amplifier is turned on. There are no user controls  
to configure. The system operates through  
multiple stages of impedance optimization,  
choosing the stage most appropriate to the actual  
impedance of the speakers you connect to it.  
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“status” led / ProteCtion CirCuitrY  
There is a single multi-color LED on the  
control panel of the amplifier to indicate the  
amplifier’s operating status. This LED’s behavior  
is as follows:  
serViCing Your Jl audio amPliFier  
If your amplifier fails or malfunctions, please  
return it to your authorized JL Audio dealer so  
that it may be sent in to JL Audio for service.  
There are no user serviceable parts or fuses inside  
the amplifier. The unique nature of the circuitry  
in the JL Audio amplifiers requires specifically  
trained service personnel. Do not attempt  
to service the amplifier yourself or through  
unauthorized repair facilities. This will not only  
void the warranty, but may result in the creation  
of more problems within the amplifier.  
aPPendix a:  
4) Alternating Red and Green: lights to indicate  
that the amplifier is experiencing a fault  
that may require service of the amplifier, its  
wiring or the vehicle’s charging system. Audio  
is muted when this fault occurs. The most  
likely cause of this fault is a low supply voltage  
condition. If battery voltage drops below 8.5  
volts at any point, the amplifier (except for the  
“Status” LED) will shut itself off to protect itself  
and the vehicle’s charging system. If the voltage  
drops below 6 volts, the “Status” LED will also  
turn off.  
Hd600/4 specifications  
Amplifier Topology: Class D, switching type with  
patented Single-Cycle Control™ technology.  
Power Supply: Pulse width modulation-regulated  
switching power supply  
1) Flashing Green: amplifier is powering up,  
audio output is muted.  
Recommended Fuse Value / Type: 50A (AFS, AGU or  
MaxiFuse™)  
Rated Power (Stereo):  
2) Constant Green: amplifier is on and  
functioning normally, audio output is active.  
150W RMS x 4 @ 1.5-4Ω (11V - 14.5V)  
Rated Power (Bridged):  
300W RMS x 2 @ 3-8Ω (11V - 14.5V)  
THD at Rated Power: <0.03% @ 4Ω per channel  
(Average at 1 kHz)  
3) Constant Red: lights to indicate that the  
amplifier has exceeded its safe operating  
temperature, putting the amplifier into a  
self-protection mode, which reduces the  
peak power output of the amplifier. The red  
light will turn green and the amplifier will  
return to full-power operating mode when its  
temperature returns to a safe level.  
The amplifier will turn back on automatically  
when voltage climbs back above 9 volts. This  
shut-down and turn-on behavior may happen  
in a rapid cycle when bass-heavy program  
material causes a weak charging system to  
momentarily dip too low. If this is happening  
in your system, have your charging system  
inspected to make sure it is working properly.  
Signal to Noise Ratio (20 kHz Bandwidth):  
Referred to Rated Power: 110 dBA  
Referred to 1 Watt: 88.2 dBA  
If you have any questions about the installation or  
setup of the amplifier not covered in this manual,  
please contact your dealer or technical support.  
Frequency Response: 6 Hz - 30 kHz (+0, -1dB)  
Damping Factor:  
300 @ 4Ω per ch. / 50 Hz  
Jl audio technical support:  
(954) 443-1100  
9:00 AM – 5:30 PM (Eastern Time Zone)  
Monday - Friday  
150 @ 2Ω per ch. / 50 Hz  
3) Constant Amber (yellow): lights to indicate  
that the impedance of the speaker load  
connected to the amplifier is lower than  
the optimum load impedance range for the  
amplifier. When this light is on, a protection  
circuit engages and reduces the power output  
of the “Front” or the “Rear” channels,  
depending on which channel is experiencing  
the problem. The amber indicator will also  
light when a short-circuit is detected in the  
speaker wiring (this can be a short between the  
positive and negative speaker wires or between  
either speaker wire and the vehicle chassis).  
This can be used to diagnose a short-circuit by  
only connecting one of the amplifier sections  
at a time (“Front” or “Rear” channels). The  
amber LED will light when you connect the  
section that is experiencing the problem and  
turn the volume up.  
Crossover Filters:  
If no problem is found with the supply  
voltage to the amplifier and you are  
still seeing alternating Red and Green  
on the “Status” LED, it is likely that the  
amplifier is suffering from an internal  
fault that requires factory service.  
Filter Sets: Two (Front Channel and Rear Channel)  
Filter Type: State-variable, 12 dB/octave Butterworth or  
24 dB/octave Linkwitz-Riley  
Filter Modes: Low-Pass or High-Pass, Defeatable.  
Cutoff Freq. Range: Continuously variable, 50 - 500 Hz  
input sections:  
For more information on troubleshooting this  
amplifier, refer to Appendix D (pages 20, 21).  
No. of Inputs: Two Stereo Pairs (Front and Rear)  
Input Type: Differential-balanced with RCA jack inputs  
Input Range: Switchable from 200mV - 2V RMS (Low)  
to 800mV - 8V RMS (High)  
There is only one condition that will shut down  
an undamaged HD600/4 completely…  
If battery voltage drops below 10 volts, the  
entire amplifier will shut itself off to protect  
itself and the vehicle’s charging system. The  
“Status” LED will turn off when this occurs. The  
amplifier will turn back on when voltage climbs  
back above 11 volts. This may happen in a rapid  
cycle when bass-heavy program material causes  
a weak charging system to dip below 10 volts  
momentarily. If this is happening in your system,  
have your charging system inspected to make  
sure it is working properly. For information on  
troubleshooting this amplifier, refer to Appendix  
D (pages 20, 21).  
Preamp output:  
2-Channel, buffered pass-through type, switch-selectable  
to pass signal from “Front” inputs only, or from all four  
inputs (summed).  
Chassis dimensions (lxwxH):  
10.74 in. x 7.85 in. x 1.93 in. (273 mm x 199.5 mm x 49 mm)  
Dimensions do not include connectors.  
Due to ongoing product development, all specifications are subject to  
change without notice.  
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aPPendix b:  
aPPendix C:  
the nine-step Procedure  
Precise Frequency selection Chart  
input sensitivity level setting  
(follow this procedure for each pair of channels)  
1) Disconnect the Speaker Connector Plugs.  
2) Turn off all processing on the source unit  
(bass/treble, loudness, EQ, etc.). Set fader  
control to center position and subwoofer  
level control to 3/4 of maximum (if  
used to drive the HD600/4). Disconnect  
the HD-RLC Remote Level Control  
temporarily (if one is being used).  
3) Switch the “Input Voltage” to “Low” and  
turn the “Input Sens.” control on both sets of  
channels all the way down.  
4) Set the source unit volume to 3/4 of full  
volume. If either set of channels is being  
driven by a source unit’s dedicated subwoofer  
output, also adjust the source unit’s subwoofer  
level control to 3/4 of maximum output. This  
will allow for reasonable gain overlap with  
moderate clipping at full volume.  
7) Connect the AC voltmeter to the “Front  
Speaker Outputs” or “Rear Speaker Outputs”  
connectors of the amplifier. If the channel pair  
is operating in stereo, it is only necessary to  
measure one channel in the pair. If bridged,  
make sure you test the voltage at the correct  
connectors (L+ and R–).  
8) Increase the “Input Sens.” control until  
the target voltage is delivered for that set  
of channels. If excessive voltage is read  
on either set of channels with the control  
at minimum (full counterclockwise),  
JL Audio amplifiers utilizing the Regulated  
Intelligent Power Supply (R.I.P.S.) allow  
delivery of their rated power when connected  
to any load impedance from 1.5 - 4Ω per  
channel and when connected to a charging  
system with any voltage from 11 - 14.5V.  
This design is beneficial for many reasons.  
One of these reasons is ease of setup.  
“Filter Freq”  
detent  
number  
Panel  
marking  
actual  
Freq.  
Full counter-clockwise: 53  
01 . . . . . . . . . . . “50” . . . . . . . . . . . .53  
02 . . . . . . . . . . . . . . . . . . . . . . . . . . . .53  
03 . . . . . . . . . . . . . . . . . . . . . . . . . . . .53  
04 . . . . . . . . . . . . . . . . . . . . . . . . . . . .53  
05 . . . . . . . . . . . . . . . . . . . . . . . . . . . .54  
06 . . . . . . . . . . . . . . . . . . . . . . . . . . . .56  
07 . . . . . . . . . . . . . . . . . . . . . . . . . . . .58  
08 . . . . . . . . . . . “60” . . . . . . . . . . . .60  
09 . . . . . . . . . . . . . . . . . . . . . . . . . . . .62  
10 . . . . . . . . . . . . . . . . . . . . . . . . . . . .64  
11 . . . . . . . . . . . . . . . . . . . . . . . . . . . .66  
12 . . . . . . . . . . . . . . . . . . . . . . . . . . . .68  
13 . . . . . . . . . . . . . . . . . . . . . . . . . . . .71  
14 . . . . . . . . . . . . . . . . . . . . . . . . . . . .74  
15 . . . . . . . . . . . . . . . . . . . . . . . . . . . .76  
16 . . . . . . . . . . . “80” . . . . . . . . . . . .80  
17 . . . . . . . . . . . . . . . . . . . . . . . . . . . .83  
18 . . . . . . . . . . . . . . . . . . . . . . . . . . . .87  
19 . . . . . . . . . . . . . . . . . . . . . . . . . . . .91  
20 . . . . . . . . . . . . . . . . . . . . . . . . . . . .94  
21 . . . . . . . . . . . . . . . . . . . . . . . . . . . .99  
22 . . . . . . . . . . . . . . . . . . . . . . . . . . . 104  
23 . . . . . . . . . . . . . . . . . . . . . . . . . . . 109  
24 . . . . . . . “12 o’clock. . . . . . . 115  
25 . . . . . . . . . . . . . . . . . . . . . . . . . . . 121  
26 . . . . . . . . . . . . . . . . . . . . . . . . . . . 128  
27 . . . . . . . . . . . . . . . . . . . . . . . . . . . 137  
28 . . . . . . . . . . . . . . . . . . . . . . . . . . . 147  
29 . . . . . . . . . . . . . . . . . . . . . . . . . . . 160  
30 . . . . . . . . . . . . . . . . . . . . . . . . . . . 174  
31 . . . . . . . . . . . . . . . . . . . . . . . . . . . 191  
32 . . . . . . . . . . . . . . . . . . . . . . . . . . . 211  
33 . . . . . . . . . . “250” . . . . . . . . . . 236  
34 . . . . . . . . . . . . . . . . . . . . . . . . . . . 269  
35 . . . . . . . . . . . . . . . . . . . . . . . . . . . 309  
36 . . . . . . . . . . . . . . . . . . . . . . . . . . . 369  
37 . . . . . . . . . . . . . . . . . . . . . . . . . . . 443  
38 . . . . . . . . . . “500” . . . . . . . . . . 484  
39 . . . . . . . . . . . . . . . . . . . . . . . . . . . 525  
Full-clockwise: 528  
Because each JL Audio amplifier will  
always deliver the same amount of power  
within its operational range of impedances  
and supply voltages, the maximum,  
switch the appropriate “Input Voltage”  
switch to “High” and re-adjust.  
unclipped output is very predictable.  
This makes setting the gain structure via the  
input sensitivity controls very simple. Following  
the directions below will allow the user to adjust  
the input sensitivity of the amplifier(s) simply  
and easily in just a few minutes using equipment  
which is commonly available in installation bays.  
9) Once you have adjusted each set of channels to  
its maximum unclipped output level, reconnect  
the speaker(s). The “Input Sens.” controls can  
now be adjusted downward if either or both  
sets of channels requires attenuation to achieve  
the desired system balance.  
5) Using the chart below, determine the  
target voltage for input sensitivity  
adjustment according to the nominal  
impedance of the speaker system  
necessary equipment  
• Digital AC Voltmeter  
• CD with a sine-wave test tone recorded at  
0 dB reference level in the frequency range  
to be amplified for that set of channels  
(50 Hz for subwoofer channels, 1 kHz for  
a midrange application). The CleanSweep®  
Calibration Disc contains the appropriate  
test tones and is available for sale at  
http://store.jlaudio.com Do not use attenuated  
test tones (-10 dB, -20 dB, etc.).  
connected to each set of outputs.  
6) Verify that you have disconnected the Speaker  
Connector Plugs before proceeding. Play a  
track with an appropriate sine wave (within the  
frequency range to be amplified by each set of  
channels) at 3/4 source unit volume.  
Front CHannels  
nom.  
rear CHannels  
impedance  
stereo  
24.5 V  
24.5 V  
24.5 V  
21.2 V  
17.3 V  
15.0 V  
bridged  
stereo  
24.5 V  
24.5 V  
24.5 V  
21.2 V  
17.3 V  
15.0 V  
bridged  
49.0 V  
Do not increase any “Input Sens.” setting in  
the system beyond the maximum level  
established during this procedure. Doing so  
will result in audible distortion and possible  
speaker damage.  
8Ω  
6Ω  
49.0 V  
42.4 V  
42.4 V  
4Ω  
34.6 V  
34.6 V  
3Ω  
30.0 V  
30.0 V  
It will be necessary to re-adjust the “Input  
Sens.” for the affected channels if any equalizer  
boost is activated after setting the “Input  
Sens.” with this procedure. This applies to any  
EQ boost circuit, source unit tone controls or EQ  
circuits. EQ cuts will not require re-adjustment.  
not recommended  
not recommended  
not recommended  
not recommended  
2Ω  
1.5Ω  
18 | JL Audio - HD600/4 Owner’s Manual  
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aPPendix d: troublesHooting  
“How do i properly set the input sensitivity on my amplifier”  
Please refer to Appendix C (pages 18, 19) to set the input sensitivity  
“my amplifier shuts off once in a while, usually at higher volumes”  
Check your voltage source and grounding point. The power supply  
for maximum, low-distortion output.  
“my amplifier doesn’t turn on”  
of the HD600/4 will operate with charging system voltages  
down to 10V. Shutdown problems at higher volume levels  
can occur when the charging system voltage drops below  
10V. These dips can be of very short duration making them  
extremely difficult to detect with a common DC voltmeter.  
To ensure proper voltage, inspect all wiring and termination  
points. It may also be necessary to upgrade the ground  
wire connecting the battery to the vehicle’s chassis and the  
power wire connecting the alternator to the battery. Many  
vehicles employ small (10 AWG - 6 AWG) wire to ground the  
battery to the vehicle’s chassis and to connect the alternator 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. Grounding problems are the  
leading cause of misdiagnosed amplifier “failures.”  
Check the fuse(s), not just visually, but with a continuity meter. It  
is possible for a fuse to have poor internal connections that  
cannot be found by visual inspection. It is best to take the  
fuse out of the holder for testing. If no problem is found with  
the fuse, inspect the fuse-holder.  
Check the integrity of the connections made to each of the  
+12VDC”, “Ground”, and Remote” terminals. Ensure  
that no wire insulation is pinched by the terminal set screw  
and that each connection is tight.  
Check to make sure there is +12V at the “Remote” connection of the  
amplifier. In some cases, the turn-on lead from the source unit  
is insufficient to turn on multiple devices and the use of a relay  
is required. To test for this problem, jump the +12VDCwire  
to the Remoteterminal to see if the amplifier turns on.  
i get a distorted / attenuated sound coming out of the speaker(s)”  
Check the speaker wires for a possible short, either between the  
“my amplifier turns on, but there is no output”  
Check the input signal using an AC voltmeter to measure the  
voltage from the source unit while an appropriate test tone is  
played through the source unit (disconnect the input cables  
from the amplifier prior to this test). The frequency used  
should be in the range that is to be amplified by the amplifier  
(example: 50 Hz for a sub bass application or 1 kHz for a full  
range / high-pass application). A steady, sufficient voltage  
(between 200mV and 8.0-volts) should be present at the  
output of the signal cables.  
Check the output of the amplifier. Using the procedure explained  
in the previous check item (after plugging the input cables  
back into the amplifier) test for output at the speaker outputs  
of the amplifier. Unless you enjoy test tones at high levels,  
it is a good idea to remove the Speaker Connector Plugs  
from the amplifier while doing this. Turn the volume up  
approximately half way. 5V or more should be measured  
at the speaker outputs. This output level can vary greatly  
between amplifiers but it should not be in the millivolt  
range with the source unit at half volume. If you are reading  
sufficient voltage, check your speaker connections as  
explained below.  
positive and negative leads or between either speaker lead  
and the vehicle’s chassis ground. If a short is present, you  
will experience distorted and/or attenuated output. The  
“Status” LED will turn amber (yellow) in this situation. It  
may be helpful to disconnect the speaker wires from the  
amplifier and use a different set of wires connected to a test  
speaker.  
Check the nominal load impedance to verify that each channel  
of the amplifier is driving a load equal to or greater than  
1.5 ohms in stereo mode (3 ohms bridged).  
Check the input signal and input signal cables to make sure signal  
is present at the Amplifier Inputs” and the cables are not  
pinched or loose. It may be helpful to try a different set of  
cables and/or a different signal source to be sure.  
“my amplifiers output fluctuates when i tap on it or hit a bump”  
Check the connections to the amplifier. Make sure that the  
insulation for all wires has been stripped back far enough to  
allow a good contact area inside the connector plugs.  
Check the input connectors to ensure that they all are making good  
contact with the input jacks on the amplifier.  
Check to ensure that the speaker wires are making a good  
connection with the metal inside the Speaker Connector  
Plugs. The speaker wire connectors are designed to accept up  
to 12 AWG wire. Make sure to strip the wire to allow for a  
sufficient connection with the metal inside each terminal.  
20 | JL Audio - HD600/4 Owner’s Manual  
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installation notes:  
use this diagram to document your amplifiers switch and control positions.  
22 | JL Audio - HD600/4 Owner’s Manual  
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