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GTQ360
User Manual
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Service Manual
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JBL GTQ360, GTQ240 User Manual

GRAND TOURING SERIES
4/3/2 Channel
Automotive Power Amplifier
GTQ360, GTQ240 Owner’s Manual
GENUINE JBL
2
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2 About Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Installation and Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.2 Controls and Connectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. System Design Using the GTQ360 and GTQ240 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1 Speaker Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.2 Signal Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.3 Remote-In/Out Connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.4 Mute Connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4.5 Speaker-Level Input Harness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
5. Internal Adjustments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
5.1 Speaker-Level Input Impedance Adjustments . . . . . . . . . . . . . . . . . . . . . . . . . . 7
5.2 Crossover Frequency Adjustments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
5.3 Custom Chip Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
6. Adjusting the Gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
7. Typical Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
8. In Case of Difficulty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Warranty Terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Owner’s Warranty Information
Model Number
Serial Number
Dealer Name
City, State, Zip
Sales Receipt Number
Date of Purchase
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 man­ual. The flexible design of their built-in crossover circuitry allows elaborate sys­tems to be built more simply than with conventional components. For optimum performance, the power amplifier circuit­ry 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 usu­ally 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 com­bined with a CD player or changer that has volume-control capability. By provid­ing 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. In addition, when using a high-powered (BTL) radio through the speaker-level inputs, Common Sense turn-on circuitry senses the common-mode voltage pres­ent on the radio’s speaker wires, turning the amplifier on without an additional remote wire.
Also, the built-in active cross-over pro­vides either full-range, high-pass or low­pass operation. This lets your GT series amplifier power either subwoofer or com­ponent 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 elec­tronic crossover.
1.2 About Installation
Although the GTQ360 and GTQ240 are designed to make installation as easy as possible, these are extremely sophisticat­ed products that require proper installa­tion and setup to realize their full perfor­mance potential. If you feel you do not have the necessary knowledge and skills,
we strongly recommend that the installa­tion be done by your authorized JBL deal­er.
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 pre­cautions and notes.
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 fea­tures a code-type security system, make certain you know the code before discon­necting the battery!
2. Run a power cable complete with a fuse (not included) directly from the posi­tive +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 professional­type, 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 con­nections. Do not use electrical tape; it will loosen with age and extreme temperatures.
3. Mount amplifier in the desired location using the included screws.
4. Connect power wiring as shown in the Wiring Diagram.
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 sig­nal 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 dam­age your speakers!
13. Turn on the signal source at a low vol­ume level, and check for the correct out­put 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.
3
2.2 Controls and Connectors
30A
30A
3
2
1
4
9
87
65
GR1
R GR1 L
LINE LEVEL
INPUT
SPEAKER LEVEL INPUTS SPEAKER OUTPUTS (BRIDGED: R+TOL–)
POWER
GR2 GR1 GR2
BATT(+)
GND
MUTE
FUSE
30A
FUSE 30A
REM
IN/OUT
L
+– –+
+– –+ + +
––––
R
PREAMP OUTPUTS
R GR2 L
L GR1 R
++
L GR2 R
15
14
13
13
12
12
11
11
10 10
14
BASS EQ OFF ON
BASS EQ OFF ON
CROSSOVER SPEAKER PREAMP
MODE INPUT MODE
R ST L+R
R ST L+RL
MIN MAX
GAIN
MIN MAX
GAIN
L
FFHH
L
GR2GR1
L
FFHH
GROUP 1
GROUP 2
CROSSOVER DESIGNATIONS F = FLAT (BYPASS) L = LOW PASS H = HIGH PASS
CROSSOVER SPEAKER PREAMP
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 sig­nals. A wire harness is supplied for use with this connector. This input also includes JBL’s Common Sense input cir­cuitry which turns the amplifier on as soon as the high-powered head unit con­nected 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 infor­mation 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” sec­tion for tips on proper setup.
4
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 high­pass 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 con­junction 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 high­pass 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 pre­amp 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 inputs for a mono output on the group. These switches do not affect the preamp ouputs.
14. Bass EQ Switch – These switches acti­vate 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.
+R to sum the left and right
3. System Design Using the GTQ360 and GTQ240
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, virtu­ally 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 cir­cuits 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 chan­nels 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.
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