JBL Stereo Amplifier GTQ240 User Manual

GRAND TOURING SERIES  
4/3/2 Channel  
Automotive Power Amplifier  
GTQ360, GTQ240 Owner’s Manual  
 
GENUINE JBL  
1. Introduction  
1.1 Thanks for purchasing your new  
GT series automotive multi-channel  
amplifier. Your GT series amplifier will  
easily connect to virtually any car audio  
system, whether it is factory installed or  
purchased separately. The GTQ360 and  
GTQ240 include an abundance of unique  
features which are described in this man-  
ual. The flexible design of their built-in  
crossover circuitry allows elaborate sys-  
tems to be built more simply than with  
conventional components. For optimum  
performance, the power amplifier circuit-  
ry is a fully-discrete design notable for its  
low distortion and unusually clean and  
clear sound quality.  
In addition to conventional preamp-level  
inputs, the GTQ360 and GTQ240 feature  
JBL’s Universal Interface™ design, which  
facilitates simple connection to factory  
radios with the low distortion that is usu-  
ally only associated with preamp level  
connection. With the Universal Interface  
on the GTQ360 and GTQ240, a factory  
radio can either be used as the main  
music source or simultaneously com-  
bined with a CD player or changer that  
has volume-control capability. By provid-  
ing this two-unit direct connection,  
Universal Interface circuitry eliminates the  
need for an FM modulator to interface a  
CD player to factory radios, improving the  
fidelity of digital playback.  
2. Installation and Use  
2.1 Refer to the “Speaker-Level Input  
Impedance Adjustments” and “Crossover  
Frequency Adjustments” sections of this  
manual (page 7) to see if you will need to  
make alterations to the factory settings. If  
you are not using the built-in crossover,  
or the speaker-level inputs, you may skip  
this step.  
1. Disconnect the negative cable from the  
battery. Note: If the vehicle’s radio fea-  
tures a code-type security system, make  
certain you know the code before discon-  
necting the battery!  
2. Run a power cable complete with a  
fuse (not included) directly from the posi-  
tive +12V battery terminal to the desired  
amplifier location. Keep the fuse within 6"  
of the battery terminal, and position it  
before the wire runs through any metal  
partition. A minimum of #10AWG is  
required for the GTQ240 and #8AWG for  
the GTQ360. The GTQ240 requires a 30A  
fuse, the GTQ360 a 60A fuse.  
Note: All wiring connections should be  
made either by soldering with heatshrink  
tubing insulation, by using commercially  
available high-quality distribution blocks,  
or with high-quality crimp-type insulated  
connectors installed with a professional-  
type, articulated crimping tool. Soldering  
crimp-type terminals is recommended for  
additional security. Never use wire nuts,  
insulation-displacement connectors (i.e.,  
ScotchLok type), or twist and tape con-  
nections. Do not use electrical tape; it will  
loosen with age and extreme  
3. Mount amplifier in the desired location  
using the included screws.  
4. Connect power wiring as shown in the  
Wiring Diagram.  
Also, the built-in active cross-over pro-  
vides either full-range, high-pass or low-  
pass operation. This lets your GT series  
amplifier power either subwoofer or com-  
ponent speakers in a bi-amplified system,  
or conventional full-range speakers in  
simpler systems.  
The GTQ360 and GTQ240 also include  
preamp-level outputs which can provide  
either full-range, high-pass or low-pass  
signal to drive additional amplifiers. This  
lets you build systems of virtually any  
design without requiring a separate elec-  
tronic crossover.  
5. Connect the outputs from the head unit  
to the appropriate inputs of the amplifier  
according to the Wiring Diagram with  
either (or both) high-quality low-level sig-  
nal cables with RCA plugs, or the supplied  
speaker-level input connector.  
6. Connect the speakers to the amplifier  
according to the Wiring Diagram.  
7. Turn the gain controls to the  
1/4-position for all groups.  
8. Set the bass boost of each group to the  
desired position.  
9. Set the crossover switches for each  
group as desired.  
10. Set the Group 2 Input as desired.  
11. Set the mode switches to Stereo,  
Left + Right, or Left Input Only operation  
for each group.  
12. Double-check your switch settings.  
Reconnect the negative battery cable.  
Note: Incorrect switch settings can dam-  
age your speakers!  
13. Turn on the signal source at a low vol-  
ume level, and check for the correct out-  
put from each speaker.  
14. Adjust the amplifier gain controls  
using the procedure described in the  
“Adjusting the Gain” section.  
15. Read the rest of the manual to get  
maximum use and enjoyment from your  
amplifier.  
1.2 About Installation  
Although the GTQ360 and GTQ240 are  
designed to make installation as easy as  
possible, these are extremely sophisticat-  
ed products that require proper installa-  
tion and setup to realize their full perfor-  
mance potential. If you feel you do not  
have the necessary knowledge and skills,  
we strongly recommend that the installa-  
tion be done by your authorized JBL deal-  
er.  
In addition, when using a high-powered  
(BTL) radio through the speaker-level  
inputs, Common Sense turn-on circuitry  
senses the common-mode voltage pres-  
ent on the radio’s speaker wires, turning  
the amplifier on without an additional  
remote wire.  
If you choose to install the GTQ amplifier  
yourself, read all of the information in this  
manual before you start the installation.  
Pay particular attention to the safety pre-  
cautions and notes.  
temperatures.  
3
 
+
)
SPEAKER LEVEL INPUTS  
SPEAKER OUTPUTS (BRIDGED:  
GR1  
R
TOL  
POWER  
REM  
IN/OUT  
LINE LEVEL  
INPUT  
PREAMP  
OUTPUTS  
L
R
L
GR2  
R
BASS EQ  
OFF ON  
MODE  
CROSSOVER  
SPEAKER  
INPUT  
GR1 GR2  
BASS EQ  
OFF ON  
MODE  
CROSSOVER  
SPEAKER  
R
GR2  
L
MUTE  
+
+
+
+
+
+
FUSE  
30A  
FUSE  
30A  
PREAMP  
L
PREAMP  
L
GR1  
GR2  
GR1  
GR2  
F
H
F
H
F
H
F
H
L
R
ST L+R  
L
R
ST L+R  
L
+
+
CROSSOVER DESIGNATIONS  
MIN MAX  
GAIN  
MIN MAX  
GAIN  
F
=
=
=
FLAT (BYPASS)  
LOW PASS  
R
GR1  
3
L
R
L
H
HIGH PASS  
BATT(+)  
GND  
GROUP  
1
GROUP  
2
1
2
4
9
5
7
6
8
14  
11  
10  
15  
12  
11  
10  
13  
12  
14  
13  
3. System Design Using  
the GTQ360 and GTQ240  
2.2 Controls and Connectors  
1. Preamp-Level Input Connector – Use  
these connectors for line-level (preamp)  
inputs to the amplifier.  
2. Preamp-Level Output Connector – Use  
these outputs to send signal to additional  
amplifiers.  
3. Speaker-Level Input Connector – Use  
this connector for speaker-level input sig-  
nals. A wire harness is supplied for use  
with this connector. This input also  
includes JBL’s Common Sense input cir-  
cuitry which turns the amplifier on as  
soon as the high-powered head unit con-  
nected to this input is turned on.  
4. Speaker Output Connectors – Connect  
speaker wiring to these connectors. See  
wiring directions for more information.  
5., 6., 7., 8. Power Connector –  
Connection for power wires REM IN/OUT  
and Mute. See wiring directions for infor-  
mation on proper connections.  
9. Fuses – GTQ240: 30A ATC type.  
GTQ360: 2 x 30A ATC type.  
10. Gain Controls – Use these controls to  
adjust the gain of the amplifier channel  
group. See the “Adjusting the Gain” sec-  
tion for tips on proper setup.  
11. Preamp Crossover Switches – These  
switches control the built-in crossovers  
that are directed to the preamp-output  
connectors. Set the switch to F (flat) for  
full-band operation for that group. Set the  
switch to L (low) to activate the low-pass  
filter on the pre-amp output group (for  
subwoofer use or to use in conjunction  
with a high-pass filtered input signal to  
create a band-pass crossover for a  
midrange or midbass driver). Set the  
switch to High-Pass to activate the high-  
pass filter for use with satellite speakers  
or tweeters on the pre-amp output group.  
12. Speaker Crossover Switches – These  
switches control the built-in crossovers  
that are connected to each group's power  
amplifier circuitry. Set the switch to F  
(flat) for full band operation on a group.  
Set this switch to L (low) to activate the  
low-pass filter on the selected amplifier  
group for subwoofer use or to use in con-  
junction with a high-pass filtered input  
signal to create a band-pass crossover  
(for a midrange or midbass driver). Set  
the switch to H (high) to activate the high-  
pass filter for use with satellite speakers  
or tweeters on an amplifier group.  
13. Mode Switches – These switches are  
used to set the input mode for both pre-  
amp and speaker-level inputs. Set the  
switch to ST(ereo) for normal operation  
on the group using individual left and  
right inputs. Set this switch to R to drive  
both the left and right outputs with only a  
single input on the right jack. Set the  
switch to L+R to sum the left and right  
inputs for a mono output on the group.  
These switches do not affect the preamp  
ouputs.  
14. Bass EQ Switch – These switches acti-  
vate a built-in Bass Boost circuit used to  
increase low-bass output on the selected  
group. These switches do not affect the  
preamp outputs.  
15. Group 2 Input Switch – This switch is  
used to select which inputs will drive  
Group 2 of the amplifier. Put the switch in  
position “GR 1” to allow Group 2 to be  
driven by the Group 1 inputs. Put the  
switch in the “GR 2” position to drive  
Group 2 with the Group 2 inputs.  
Power Indicator LED (on amp chassis  
top) – LED steadily illuminates for normal  
operation. LED blinks when protection  
circuitry or muting is engaged.  
3.1 Speaker Requirements  
When used in the non-bridged mode, a  
group-channel of the GTQ360 or GTQ240  
can easily drive two 2-ohm speaker loads.  
When only one speaker is connected to  
the left and right outputs of a group, virtu-  
ally any conventional speaker may be  
used. Although the amplifier will not be  
damaged, load impedances lower than 2  
ohms will eventually cause the amplifier  
to overheat, activating the protection cir-  
cuits and causing the unit to shut off until  
it cools down sufficiently.  
When a group is in bridged mode, the  
combined impedance of the speaker (or  
speakers) connected to the bridged chan-  
nels should be at least 4 ohms. Sustained  
operation of the unit in bridged mode  
with less than 4 ohms will likely cause  
overheating.  
The GTQ360 or GTQ240 must not be used  
with speakers that have either one of  
their input terminals wired to the frame  
of the speaker or to the chassis of the  
vehicle.  
4
 
4.3 Remote-In/Out Connection  
• The remote power control system turns  
the GTQ amplifier off when not in use to  
prevent discharging of the vehicle’s bat-  
tery. Because the JBL GTQ amplifiers  
include Common Sense 2-way turn-on,  
when using the speaker-level inputs with  
a head unit that includes a BTL power  
amp it is not necessary to connect the  
remote wire. The amplifier will automati-  
cally activate whenever you turn on the  
head unit. If you are using the line-level  
inputs, or the speaker-level inputs with a  
head unit that does not have a BTL power  
amp, use the following remote wire con-  
nections.  
Using the REM-IN feature – When +12  
volts is applied to the remote IN/OUT ter-  
minal the amplifier is turned on. A red  
LED on the top panel of the amplifier will  
illuminate to indicate the amplifier is on.  
If the head unit has a +12 volt automatic  
antenna or amplifier remote activation  
wire, connect it to the REM-IN/OUT con-  
nector on the GTQ amplifier. When the  
amplifier is turned on, there is a time  
delay of several seconds (longer in cold  
weather) before the amplifier will produce  
sound. This eliminates the chance of  
annoying noises produced by the radio or  
signal processors being amplified and  
passed to the speakers when the system  
is first activated.  
4. Wiring  
4.1 Wiring  
Proper wiring of the GTQ amplifiers and  
the associated components is extremely  
important for proper performance and  
long-term reliability. Using the proper  
type of wire is very important.  
3.2 Signal Sources  
The low-level preamp outputs of any  
radio/tape deck, CD player, or preamp/  
equalizer so equipped can drive the  
GTQ360 or GTQ240. The gain controls of  
the amplifier are used to match its input  
sensitivity to the output voltage of the  
source. This matching is important to  
keep noise low and is explained in the  
“Adjusting the Gain” section of this  
manual.  
Route the wiring through the car carefully.  
Do not allow wires to lay against sharp  
sheet metal edges or any other surfaces  
that might wear away or cut through the  
insulation of the wire. Use insulated strain  
reliefs, rubber grommets and plastic tub-  
ing to protect the wires whenever they are  
run through sheet metal panels or are  
placed where they might be pulled or  
damaged.  
Parallel Wiring  
(+)  
Thanks to Universal Interface Circuitry,  
the GTQ360 or GTQ240 can also be con-  
nected to power amplifiers, radios or  
equalizers that are equipped with only  
speaker outputs by connecting them  
through the speaker-level input connec-  
tor. Inside the GTQ360 and GTQ240, the  
speaker-level and preamp-level inputs are  
connected through a mixing circuit, which  
allows them to be used simultaneously.  
Therefore a low-level source, such as a  
CD player equipped with a volume con-  
trol, may be connected to the preamp-  
level inputs at the same time as a pow-  
ered radio/tape unit is connected to the  
speaker-level inputs. This provides a high-  
er performance alternative to an FM mod-  
ulator connection when you wish to add  
CD capability to a factory cassette stereo.  
Switching from one source to the other is  
as simple as turning the desired source  
on and turning the undesired one off —  
no additional switches or relay connec-  
tions are needed.  
2 ohms  
Nominal  
Impedance  
4 ohms  
4 ohms  
4.2 Ground Wire  
• Proper grounding is extremely impor-  
tant. Use a heat- and oil-resistant stranded  
copper automotive wire equivalent to the  
size used for the +12V connection. Crimp  
or solder and insulate any wire-to-wire  
connections. Keep the ground wire as  
short as possible. A ground wire must be  
solidly connected to a major sheet-metal  
structure of the vehicle such as a panel  
near the amp-mounting location. Scrape  
all paint and primer off the sheet metal at  
the grounding point to ensure a good  
electrical connection. Attach the wire to  
the grounding point with a nut, bolt and  
star washer. The high current demanded  
by high-powered amplifiers requires a  
more secure ground than the typical  
sheet-metal screw will provide. Coat the  
connection with silicon sealant for better  
long-term reliability.  
(–)  
Series Wiring  
(+)  
4 ohms  
• Some head units have no automatic  
antenna or power amp activation wire.  
Others have automatic antenna wires that  
are “on” only when the radio is used but  
not when a tape is played. In such cases,  
connect the remote-in turn-on terminal to  
an unused accessory terminal in the fuse  
block, or any other +12 volt source that is  
turned on and off with the vehicle’s igni-  
tion switch. The remote on/off system  
8 ohms  
Nominal  
Impedance  
4 ohms  
(–)  
5
 
Subwoofer (Low-Pass)  
A. Satellite/Subwoofer  
Cassette/CD Tuner  
Speaker-Level Output Connection  
(Use only when line-level output  
is not available)  
(–)  
(+)  
High-Pass Satellite  
Crossover Frequency: 100Hz  
CD Player  
or Changer  
Cassette/CD Tuner  
Tweeter/Midrange Satellites  
(High-Pass)  
Left  
Right  
C: 300µF capacitor  
100V, non-polarized  
(–)  
(+)  
C
(+)  
C
(–)  
L
Subwoofer Low-Pass  
Crossover Frequency: 100Hz  
Antenna Input  
L: 6.2mH air core inductor  
CD Input  
Amplifier  
Speaker  
Level  
Power  
Antenna  
Cassette/Receiver  
Power Supply  
Wires  
Inputs  
GTQ360  
Power  
Antenna  
Relay  
Amplifier  
Amplifier  
Power  
+
)
Cassette/CD Preamp Output  
SPEAKER LEVEL INPUTS  
SPEAKER OUTPUTS (BRIDGED:  
GR1  
R
TOL  
LINE LEVEL  
INPUT  
PREAMP  
OUTPUTS  
GR2  
Speaker  
Output  
POWER  
R
GR2  
L
L
R
L
GR2  
R
REM  
IN/OUT  
Connection  
+
+
+
+
+
+
FUSE  
30A  
FUSE  
30A  
MUTE  
GR1  
GR2  
GR1  
Connection  
L
+
+
R
GR1  
L
R
BATT(+)  
GND  
*You may change the subwoofer satellite crossover frequency by using the  
Inductor and Capacitor values calculated with the following formulas:  
+
Speakers  
Speakers  
30,000  
High-Pass (Satellite Crossover):  
= New Capacitor Value in µF  
Blue w/White Stripe - Remote On/Off  
Desired crossover Frequency in Hz  
Amplifier  
+
+
Speaker  
Output  
Connection  
Ignition Switch  
620  
Low-Pass (Subwoofer Crossover):  
= New Inductor Value in mH  
Desired crossover Frequency in Hz  
(Not Included)  
Center Channel  
Bridged Speaker Connection*  
Fuse  
+
B. Center Channel  
Main +12V  
+
Amplifier  
Speaker  
Output  
( – )  
Minimum  
( + )  
Vehicle Battery  
8
Connection  
8
L-Pad  
(Optional but Recommended)  
Power Ground  
GTQ360  
Chassis Ground  
+
)
SPEAKER LEVEL INPUTS  
SPEAKER OUTPUTS (BRIDGED:  
GR1  
R
TOL  
LINE LEVEL  
INPUT  
PREAMP  
OUTPUTS  
GR2  
POWER  
R
GR2  
L
L
R
L
GR2  
R
REM  
FUSE IN/OUT  
30A  
+
+
+
+
+
+
FUSE  
30A  
MUTE  
GR1  
GR2  
GR1  
L
+
+
R
GR1  
L
R
draws negligible current so a relatively  
small (18 or 20 gauge) wire may be used.  
Using the REM-OUT feature – The REM-  
IN/OUT terminal of the GTQ amplifier  
may be used to turn on other amplifiers  
when the GTQ amplifier is being turned  
on by the Common Sense circuitry in the  
speaker-level input. Simply connect the  
head unit speaker-level outputs to the  
GTQ amplifier speaker-level inputs and  
connect the REM-IN/OUT terminal to the  
remote-in terminal of other amplifiers or  
signal processors. The GTQ amplifier will  
turn on the other amps or processors  
whenever the Common Sense circuitry  
turns on the GTQ amplifier.  
BATT(+)  
GND  
* Center Channel Speaker Minimum 8 Ohms, Main  
Speakers Minimum 4 Ohms When Used Simultaneously.  
( + )  
4Minimum  
( – )  
( – )  
( + )  
Stereo, Non-Bridged  
Speaker Connection*  
4Minimum  
Simultaneous Stereo-Mono Connection Diagrams  
6
 
5. Internal Adjustments  
5.1 Speaker-Level Input  
Impedance Adjustments  
The speaker level inputs of the GTQ  
amplifiers come factory-set with  
5.2 Crossover Frequency  
Adjustments  
5.3 Custom Chip Construction  
Regardless of whether you build or buy it,  
the necessary resistor network has the  
following configuration:  
The GTQ amplifiers include built-in  
frequency selectable crossovers. One  
crossover is connected in series with the  
amplifier circuitry and the other cross-  
over is connected to the preamp level out-  
put jacks. These crossovers can be set in  
either the “F” (full bandwidth operation),  
“L” (subwoofer operation), or “H” (satel-  
lite operation).  
100k ohm input impedance. This will pro-  
vide the lowest distortion operation from  
the speaker outputs of most modern head  
units by reducing the power the amplifier  
in the head unit must deliver to practi-  
cally, nothing. On some older or lower-  
priced head units this load will not facili-  
tate proper fader operation. To allow for  
this, we have provided the ability to  
change the input impedance of the speak-  
er-level inputs to 15 ohms. This is accom-  
plished by moving the jumpers shown on  
the diagram below. This input is also  
capable of directly accepting signals,  
when in the 100k ohm setting, from many  
Balanced Line Drivers such as those  
sometimes used in competition vehicles.  
If the head unit has 4 channels of built-in  
amplification and/or an electronic fader  
control, you should leave the jumpers in  
the factory-set position.  
The crossover frequencies are set by  
chips inside the amplifier. These chips are  
simply a set of resistors, connected  
across the pins and molded into a single  
package. The crossover frequencies may  
be changed to any value desired by  
changing the resistor network. JBL has  
chips available in the popular values list-  
ed in the table which follows. If none of  
these suit your system, you may purchase  
compatible resistor networks from a local  
electronics store, or you may build your  
own custom values from discrete resis-  
tors mounted on a 14-pin DIP Header  
using the instructions which follow.  
4.4 Mute Connection  
The GTQ amplifier includes a mute input  
terminal. This amplifier will mute when a  
5V to 12V DC signal is applied to the  
“mute” input and will be in normal oper-  
ation mode with either a ground or noth-  
ing connected to the “mute” input. This  
“mute” input is compatible with any  
aftermarket noise gate that puts out a  
control voltage of +5V to +12V DC.  
• Each resistor in the package has the  
same value.  
• If you know the crossover frequency you  
want, you can calculate the resistor value  
necessary by solving the following equa-  
tion:  
Resistor  
Value  
in ohms  
2,500,000  
Frequency in Hz  
=
If the head unit has 2 channels of amplifi-  
cation, with a speaker-level fader, the  
jumpers should be set to the 15-ohm  
position. This will always be a rotary-type  
control, not one controlled by electronic  
pushbuttons.  
4.5 Speaker-Level Input  
Harness  
• Use the following equation if you have a  
resistor pack of a known value, and want  
to find its crossover frequency:  
Frequency Resistor JBL Part  
Color Codes  
Value  
Number  
Group 1 Left (+):  
Group 1 Left (–):  
White  
50Hz  
80Hz  
47k  
33k Ω  
22k Ω  
12k Ω  
10k Ω  
6.8k Ω  
4.7k Ω  
3.9k Ω  
1k Ω  
1-23-750  
1-23-817  
1-23-820  
1-23-821  
1-23-810  
1-23-822  
1-23-815  
1-23-823  
1-23-824  
1-23-816  
White with  
Black Stripe  
Gray  
Gray with  
Black Stripe  
Green  
Green with  
Black Stripe  
Purple  
Purple with  
Black Stripe  
2,500,000  
Resistor Value in ohms  
Frequency  
in Hz  
JUMPER SELECTOR  
SELECT 100K OR 15 OHMS  
=
Group 1 Right (+):  
Group 1 Right (–):  
120Hz  
200Hz  
250Hz  
375Hz  
500Hz  
650Hz  
2.5kHz  
5kHz  
• To build chips from discrete resistors,  
solder the resistors to a standard 14-pin  
“DIP Header” according to the diagram. If  
a DIP Header is not available, you may  
bend the leads of 1⁄4-watt resistors 90  
degrees, trim them to 3mm-length, and  
insert them directly into the chip sockets.  
Group 2 Left (+):  
Group 2 Left (–):  
100K  
15  
LINE INPUT  
3
BAT  
Group 2 Right (+):  
Group 2 Right (–):  
3
GND  
REM  
OUT  
470 Ω  
7
 
BEST-Vertical Mounting  
To change the crossover frequency  
change the resistor network as follows:  
1. Remove the screws from the bottom  
panel as shown below.  
AIR FLOW  
6. Adjusting the Gain  
Before operating the GTQ amplifiers,  
recheck all wiring connections to make  
sure they are correct and secure. Be sure  
that a fuse (not included) is installed in the  
7. Typical Applications  
The following diagrams show the most  
common basic system configurations of  
the GTQ amps. One or more of these  
building blocks may be combined to form  
elaborate system designs.  
The GTQ amps use the terminology  
“Group 1” and “Group 2” to indicate the  
two main signal paths within the amplifi-  
er. Each “group” may consist of a mono  
bridged signal or a stereo pair of L+R  
signals depending on the system  
configuration.  
+
12V line near the battery. Reconnect the  
negative ground (–) terminal of the bat-  
tery. Make sure that the mode switches,  
crossover switches, Group 2 Input switch-  
es, and crossover frequency modules are  
properly set.  
• The setting of the gain controls on the  
GTQ amplifiers is important to ensure  
proper performance, low noise levels, and  
maximum reliability in the system.  
Using a high signal level from the source  
and a low gain setting on the amplifier  
will help keep background noise levels in  
the system low.  
• To adjust a system using a single GTQ  
amplifier, start with both of the amplifier  
gain controls fully counterclockwise. Set  
all bass/treble or equalizer controls to  
their centered or bypassed positions.  
While listening carefully to the system  
output, adjust the volume control of the  
radio/tape deck to the point where you  
first begin to hear audible distortion.  
Use caution: excessive distortion can  
damage loudspeakers. Reduce the level  
just to the point where the distortion goes  
away. If this setting does not provide ade-  
quate volume levels, gradually increase  
(turn clockwise) the gain control for the  
main (usually front) speaker groups on  
the GTQ amplifier until the system plays  
as loud as necessary or when the first  
signs of distortion are heard.  
2. Select which resistor module, high  
pass or low pass, that you wish to  
change.  
3. A chip puller, which can be obtained  
from any electronics store, is recom-  
mended to remove the resistor chip. Pull  
the resistor chip from the socket as  
shown in the figure below.  
GOOD-Horizontal Mounting  
AIR FLOW  
NEVER-Mount Upside Down  
System 1  
Active 3-way using outboard tweeter amplifier  
Speaker Preamp Group  
Front  
JBL C.  
Output  
Output  
2
JBL GTS600REV  
A
PC00108800  
NORRIDGE, CA  
Mode CrossoverCrossover Input X-over Frequency  
FILTER  
LOW PASS  
CROSSOVER  
FREQUEELENC  
S T  
MCOYIODUNLE  
GR 1  
GR 2  
Stereo  
Stereo  
Low  
Low  
High  
High  
GR 2  
5k**  
80Hz**  
C10  
C13  
FILTER  
HIGH PASS  
FREQUEELENC  
S T  
MCOYIODUNLE  
* A single (mono) subwoofer may be used by setting GR 2  
mode to "L+R."  
** The crossover frequencies listed are suggestions. Actual  
crossover points should be determined from  
loudspeaker requirements.  
4. Place the new module in the socket  
making sure all pins are lined up with the  
socket holes. Press the module firmly into  
the socket.  
GR 1  
Input  
GR 1  
GR 2 GR 2  
Input  
Pre Out Input Pre Out  
LOW-POWER  
STEREO AMP  
GTQ AMP  
5. Replace the bottom lid.  
For further information on how to use the  
speaker output and preamp output  
crossovers for system building see the  
“Typical Applications” and “Add-On and  
Upgrade Steps” sections.  
GR 1  
GR 2  
+
+
+
+
+
L
+
L
R
L
R
R
Tweeters  
Midbass  
Subwoofers*  
8
 
L
R
L
R
L
R
L
R
Preamp or  
Preamp or  
Front  
Rear  
Speaker-Level  
Input  
Application 3  
4-Channel Bi-Amplified System with  
Non-Fading Subwoofers  
Application 1  
4-Channel Full-Range  
Front  
Rear  
Speaker-Level  
Input  
L
R
L
R
L
R
L
R
GR 1  
GR 2  
GR 1  
GR 2  
Group 1  
ST  
Flat  
Group 2  
ST  
GR 2  
Flat  
Input Mode  
Group 2 Input  
Speaker Crossover  
Preamp Output Crossover  
Group 1  
Stereo  
High Pass Low Pass  
Group 2  
Stereo  
GR 1+2  
Mode  
GTQ  
AMP  
GTQ  
AMP  
Group 2 Input  
Speaker Crossover  
Preamp Crossover  
GR 1  
GR 2  
GR 1  
GR 2  
+
L
L
+
L
L
+
L
+
L
L
L
R
+
R
R
+
R
R
+
R
R
+
R
+
+
+
+
+
+
+
+
L
R
L
R
L
R
L
R
Subwoofers  
Front Speakers  
Rear Speakers  
Front Speakers  
Application 4  
Application 2  
2-Channel Bridged  
3-Channel Bi-Amplified System with  
Non-Fading Mono Subwoofer  
L
R
L
R
L
R
Preamp or  
Output  
Front  
Rear  
Speaker-Level  
Input  
2-Channel Input  
L
R
L
R
GR 1  
GR 2  
Group 1  
Group 2  
R
GR 2  
*
Group 1  
Stereo  
Group 2  
L+R  
GR 1+2  
R
R
GR 2  
GR 1  
Input Mode  
Group 2 Input  
Speaker Crossover  
Preamp Output Crossover  
R
*
Mode  
Group 2 Input  
Speaker Crossover  
Preamp Crossover  
High Pass Low Pass  
GTQ  
AMP  
*Set to Low Pass for subwoofers, High Pass for satellites  
or Flat for full range.  
GTQ  
AMP  
GR 1  
GR 2  
+
L
L
+
L
R
GR 2  
GR 1  
R
+
R
+
R
+
R
L
L
+
+
+
+
+
L
R
L
R
Front Speakers  
Satellite Speakers  
Subwoofer  
9
 
8. In Case of Difficulty  
Power-on light does not come on  
• Head unit not on; turn the head unit on.  
• Ground wire is disconnected or defec-  
tive; check for continuity with an ohm-  
meter between the amplifier’s ground ter-  
minal and a known chassis ground point.  
• Battery wire is disconnected or defec-  
+
tive; check for approximately 12 volts  
Power light is on, but no sound is heard  
from some or all of the speakers  
• Defective head unit or signal processor;  
check each component for proper wiring  
and operation.  
• Defective GTQ amplifier; if there is audio  
signal present at the inputs of the amplifi-  
er and there is no output, the GTQ amplifi-  
er may be defective.  
between the amplifier’s battery and  
ground terminals.  
• Blown fuse; check amplifier’s fuses  
located on the end panel near the power  
connector. If they are blown, replace them  
with identical ones. If the new fuses blow  
immediately, check all the wiring connec-  
tions. If the source of the problem cannot  
be determined, consult your JBL dealer.  
• Remote-on wire between the head unit  
and the amplifiers is disconnected or  
Alternator whine through the audio sys-  
tem with the engine running  
+
defective; check for 12 volts between  
amplifier's remote-on input terminal and  
the ground wire with the head unit on.  
• Ground loops; follow the wiring sugges-  
tions in the section called “Solving Noise  
Problems.” Also, verify that the chassis  
grounding point you have chosen is true  
ground by checking for continuity  
between the chassis ground point and  
battery ground.  
Power light is on, but no sound is heard  
from some or all of the speakers  
• Incorrect switch settings; make sure that  
all switches (mode, input and crossover)  
are in their correct positions for your sys-  
tem configuration.  
• Incorrectly connected or shorted speaker  
wires; check for shorts in wiring.  
• Defective or disconnected audio cables;  
check for continuity and replace if  
necessary.  
Bass output from speakers too low  
• Speaker wired out of phase; check for  
+
proper polarity on all speaker wiring (  
+
amp terminal to speaker terminal and –  
amp terminal to – speaker terminal).  
Power light is blinking and no sound is  
heard  
• Incorrect gain adjustment; verify that the  
amplifier gain controls are not turned  
completely down. If they are, sound out-  
put level may be very low and may give  
the impression that the system (or part of  
the system) is dead.  
• Incorrectly connected or shorted speaker  
wires; check for shorts in wiring.  
• Defective GTQ amplifier; if there is no  
short on the speaker outputs, the GTQ  
amplifier may be broken. Consult your  
JBL dealer.  
10  
 
Specifications  
GTQ360  
GTQ240  
Power Output  
(20Hz – 20kHz,  
14.4V Battery Voltage)  
60 Watts x 4 (4 Ohms, 0.05% THD)  
90 Watts x 4 (2 Ohms, 0.08% THD)  
180 Watts x 2 (Bridged 4 Ohms, 0.08% THD)  
45 Watts x 4 (4 Ohms, 0.05% THD)  
60 Watts x 4 (2 Ohms, 0.08% THD)  
120 Watts x 2 (Bridged 4 Ohms, 0.08% THD)  
Signal-to-Noise Ratio  
Frequency Response  
100dBA  
100dBA  
10Hz – 50kHz (+0, –1dB)  
10Hz – 50kHz (+0, –1dB)  
20Hz – 20kHz (+0, – 0.1dB)  
20Hz – 20kHz (+0, – 0.1dB)  
Damping Factor  
Slew Factor  
> 200  
> 200  
> 5  
> 5  
Line-Level Input Sensitivity  
(For Rated Power)  
100mV – 4V RMS  
100mV – 4V RMS  
Line-Level Input Impedance  
10k Ohms  
10k Ohms  
Speaker-Level Input Impedance  
15 Ohm or 100k Ohm  
15 Ohm or 100k Ohm  
(Selectable by Internal Jumpers)  
(Selectable by Internal Jumpers)  
Speaker-Level Input Sensitivity  
200mV – 8V RMS  
200mV – 8V RMS  
Preamp Output Level  
Preamp Input:  
V out = V in  
V out = V in  
Speaker Input:  
V out = 1/2 V in  
V out = 1/2 V in  
Minimum Speaker Impedance  
Single-Ended (Non-Bridged):  
Bridged:  
2 Ohms  
4 Ohms  
2 Ohms  
4 Ohms  
Built-in Electronic  
Crossover Frequency and Slope  
18dB per Octave Low-Pass Filter,  
Frequency Chips Available from 50Hz – 5kHz  
Factory Setting: 80Hz  
18dB per Octave Low-Pass Filter,  
Frequency Chips Available from 50Hz – 5kHz  
Factory Setting: 80Hz  
18dB per Octave High-Pass Filter,  
Frequency Chips Available from 50Hz – 5kHz  
Factory Setting: 80Hz  
18dB per Octave High-Pass Filter,  
Frequency Chips Available from 50Hz – 5kHz  
Factory Setting: 80Hz  
Bass Boost Frequency and Magnitude  
Mute Trigger Voltage  
Power Requirement  
Fuse Size  
+4dB at 40Hz  
+4dB at 40Hz  
5V to 12V  
5V to 12V  
11 to 16V DC Negative Ground  
30 Amp ATC Type Fuse (2 per Amplifier)  
11 to 16V DC Negative Ground  
40 Amp ATC Type Fuse  
Size (HxWxL)  
2 x 11-1/4 x 14"  
2 x 11-1/4 x 12"  
(51 x 286 x 356mm)  
(51 x 286 x 305mm)  
Weight  
13.5 lbs (6.12 kg)  
Molex Mini-Fit Jr  
11.1 lbs (5.03 kg)  
Molex Mini-Fit Jr  
Speaker-Level Input  
Mating Connector  
#39-01-2080  
#39-01-2080  
Metal Pins: 39-00-0038  
Metal Pins: 39-00-0038  
11  
 
Declaration of Conformity  
WarrantyTerms:  
1 Year Transferable Limited Warranty / 2 Year Extended Transferable Limited Warranty (USA Only)  
We, JBL Europe A/S  
Kongevejen 194B  
DK-3460 Birkerød  
DENMARK  
This is an important document.  
Attach your bill of sale to  
this page and keep it in a safe  
place. Your bill of sale is your  
warranty.  
The JBL warranty remains in effect for one  
year from the date of the first consumer  
purchase unless installed by an authorized  
JBL dealer. Installation by an authorized JBL  
dealer will extend the warranty to a period  
of two years.  
declare in own responsibility, that the products described  
in this owner’s manual are in compliance with technical  
standards:  
EN 55 020 /6.1988  
EN 50 082-1/3.1995  
the instruction manual; damage resulting  
from the performance of repairs by some-  
one not authorized by JBL; damage caused  
by installation of parts that do not conform  
to JBL specifications; units used for com-  
mercial or business use; any claims based  
on misrepresentations by the seller; prod-  
ucts sold on an “as-is” or final sale basis; or  
the cost of installing, removing, or rein-  
stalling the unit. JBL’s liability is limited to  
the repair or replacement, at our option, of  
any defective product and shall not include  
incidental or consequential damages. JBL  
reserves the right to replace a discontinued  
model with a comparable model. Any  
replacement units or parts may be new  
or rebuilt.  
Do Not Return Products to  
the JBL Factory without  
Authorization. They will be  
Steen Michaelsen  
JBL Europe A/S  
Birkerød. DENMARK. 5/97  
Returned Unopened.  
Who is Protected by  
this Warranty  
You are responsible for transporting your  
product for repair or replacement. JBL will  
pay reasonable return charges for delivery  
to any location in the United States if the  
repair or replacement is covered under  
the warranty.  
The JBL warranty protects the original  
owner and all subsequent owners providing  
that the JBL product was purchased from an  
authorized dealer in the United States or  
purchased by military personnel from an  
authorized military outlet. A copy of the  
original dated bill of sale must be presented  
whenever warranty service is required.  
Correspondence with JBL should be  
addressed to: JBL Customer Service, 80  
Crossways Park West, Woodbury, NY 11797  
or fax us at 516-496-0812. Outside the  
United States, please contact your local  
distributor.  
This warranty gives you specific legal rights.  
You may also have other rights which vary  
from state to state. Some states do not  
allow the exclusion or limitation of  
incidental or consequential damages or lim-  
itations on how long an implied warranty  
lasts, so the above may not apply to you.  
JBL Consumer Products  
80 Crossways Park West  
Woodbury, NY 11797  
What is Covered by  
this Warranty  
To Obtain Warranty Service  
If you require warranty service, please  
return the product to your dealer. If this is  
not possible and you live in the United  
States, please call 1-800-336-4JBL for  
information on how to obtain service or  
replacement. If purchased outside the  
United States, contact your local dealer for  
repair or replacement.  
8500 Balboa Blvd.  
Northridge, CA 91329  
Except as specified below, the JBL warranty  
covers all defects in material and workman-  
ship. The following are not covered:  
Damage caused by accident, misuse, abuse,  
product modification or neglect; damage  
occurring during shipment; damage from  
failure to follow instructions contained in  
800-336-4JBL (4525)  
A Harman International Company  
Part No. GTQ360/240OM  
Made in USA  
 

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