GTH400-20107 06/03/98 15:49 Side 26
GTH400-20107 06/03/98 15:49 Side 1
GTH400
6/5/4/3 CHANNEL AUTOMOTIVE POWER AMPLIFIER
OWNER’S MANUAL
GTH400-20107 06/03/98 15:49 Side 2
Table of Contents
1. Introduction...................................................................................... 3
1.1 Features .................................................................................... 4
1.2 About Installation ...................................................................... 4
2. Installation and use .......................................................................... 5
3. System Design with the GTH400..................................................... 6
3.1 Speaker Requirements ............................................................. 6
3.2 Typical Applications.................................................................. 7
4. Installation and Use ......................................................................... 9
4.1 Controls and Connectors.......................................................... 9
4.2 Internal Adjustments ................................................................ 12
Speaker-Level Input Impedance Adjustments......................... 12
Crossover Frequency Adjustments.......................................... 12
Custom Chip construction ....................................................... 13
Remote Chassis Installation .................................................... 13
Unter-Dash Remote Installation............................................... 14
In-Dash remote Installation ...................................................... 14
Power Supply Connections ..................................................... 14
Simultaneous Speaker Stereo-Mono Connection Diagram..... 16
Speaker-Level Input Harness - Color Codes........................... 17
5. Adjusting the Gain .......................................................................... 17
6. Important Characteristics ............................................................... 19
7. In Case of Difficulty......................................................................... 21
8. Specifications ................................................................................. 23
Owner’s Warranty Information
Model Number
Serial Number
Dealer Name
City, State, Zip
Sales Receipt Number
Date of Purchase
GTH400-20107 06/03/98 15:49 Side 3
1. Introduction
Thanks for purchasing your new GT series automotive multichannel amplifier. Your GT series amplifier will easily connect to virtually any car audio system, whether it is factory installed or one purchased separately. The GTH400 includes an abundance of unique features which are described in this manual. The most obvious feature of the GTH400 is its 6-channel, staggered-power design. This design provides the simplicity of driving an entire system with a single amplifier without compromise. The flexible design of the GTH400’s built-in crossover circuitry also 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 preamplevel inputs, the GTH400 features 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. 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.
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GTH400-20107 06/03/98 15:49 Side 4
1.1 Features
Theory of Operation –
Virtual Center Image Enhancer
JBL’s breakthrough “Virtual Center” circuitry is the result of the understanding of how the human ear responds to timing, frequency, and amplitude cues to determine the apparent direction of a sound source.
Virtual Center circuitry manipulates the analog signal in real time to provide each of the driver’s ears with the signal they would receive if the driver was seated in the center of the vehicle. This provides a stable, centered image to the driver much like that obtained with a dedicated center-channel loudspeaker.
To restore the spaciousness that is generally lost in the small confines of a car interior, the rear channels utilize differential-mode ambience recovery to restore the ambience information present in all conventional stereo recordings. Unlike DSP, the JBL circuitry does not add synthetic reverb, but recovers real information that is masked in conventional systems. As a result, the overall effect from the Virtual
Center circuitry of the GTH400 is incredibly realistic, yet simple to adjust and use. Best of all, the “Virtual Center” and ambiance recovery circuits do not require specially encoded recordings and work with virtually all conventional stereo tapes, discs, and broadcasts.
1.2 About Installation
Although the GTH400 is designed to make installation as easy as possible, it is an extremely sophisticated product that requires proper installation and setup to realize its 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 GTH400 yourself, read all of the information in this manual before you start the installation. Pay particular attention to the safety precautions and notes.
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GTH400-20107 06/03/98 15:49 Side 5
2. Installation and use
Refer to the “Crossover Frequency
Adjustments” and “Speaker-Level Input
Impedance Adjustments” sections of this manual to see if you will need to make alterations to their factory settings.
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 minimum AWG #8 power cable complete with a 60 amp 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.
3. Note: All wiring connections should
be made either by soldering with heatshrink tubing insulation 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 connections. Do not use electrical tape; it will loosen with age and extreme temperatures.
4. Mount amplifier in the desired location using the included screws.
5. Connect power wiring as shown in the Wiring Diagram on page 18.
6. Connect the outputs from the head unit to the appropriate inputs of the amplifier according to the Wiring
Diagram (page 18) with either (or both) high quality low-level signal cables with RCA plugs, or the supplied speaker-level input connector.
7. Install the remote control in the desired location. Connect and run the cable from the remote to the amplifier.
8. Connect the speakers to the amplifier according to the Wiring Diagram on page 18.
9. Turn the gain controls to the
1/4-position for all groups.
10. Set the bass boost of each group to the desired position.
11. Set the crossover switches for each group as desired.
12. Set the Group 2 Input and Group 3
Input as desired.
13. Set the mode switches to Stereo,
Left + Right, or Left Input Only operation for each group.
14. Double-check your switch settings.
Reconnect the negative battery cable. Note: Incorrect switch settings can damage your speakers!
15. Turn on the signal source at a low volume level, and check for the correct output from each speaker.
16. Adjust the amplifier gain controls using the procedure described in the “Adjusting the Gain” section
(page 25).
17. Read the rest of the manual to get maximum use and enjoyment from your amplifier.
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GTH400-20107 06/03/98 15:49 Side 6
6
3. System Design Using the GTH400
3.1 Speaker Requirements
When used in the non-bridged mode a group-channel of the GTH400 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. When two speakers are connected in parallel to a single output
(left or right) of a given group, each speaker must have a minimum impedance of at least 4 ohms. This ensures that the combined load will not drop below 2 ohms. 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.
Parallel Wiring
(+)
2 ohms
Nominal
Impedance
(–)
4 ohms 4 ohms
When a group of the GTH400 is in bridged mode, the combined impedance of the speaker (or speakers) connected to the bridged channels should be at least 4 ohms. As in the example above, sustained operation of the GTH400 in bridged mode with less than 4 ohms will likely cause overheating.
The GTH400 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.
(+)
8 ohms
Nominal
Impedance
(–)
Series Wiring
4 ohms
4 ohms
GTH400-20107 06/03/98 15:49 Side 7
3.2 Typical Applications
The diagrams on pages 8 & 9 show the most common basic system configurations of the GTH400. One or more of these building blocks may be combined to form elaborate system designs.
The GTH400 uses the terminology
“Group 1,” “Group 2” and “Group 3” to indicate the three main signal paths within the amplifier. Each “group” may consist of a mono bridged signal or a stereo pair of L+R signals depending on the system configuration.
Application 1
6-Channel Bi-Amplified System with
Non-Fading Subwoofers
Mode
Group 2 Input
Group 3 Input
Speaker Crossover
Preamp Crossover
L
Front
L
GR 1
R
Preamp or
L
Speaker-Level
R
Input
L
Group 1
Stereo
Group 2
Stereo
Group 3
Stereo
– GR 2 –
– – GR 1+2
High Pass High Pass Low Pass
– – –
GTH400
GR 1
L– L+
R– R+
L–
R
Rear
R
GR 2
GR 2
L+
R– R+
L– L+
R–
GR 3
R+
– + –
L R
Front Speakers
+ – + –
L R
Rear Speakers
+ – + –
L R
Subwoofers
+
Application 2
5-Channel Bi-Amplified System with
Non-Fading Mono Subwoofer
Mode
Group 2 Input
Group 3 Input
Speaker Crossover
Preamp Crossover
L
Front
L
GR 1
R
Preamp or
L
Speaker-Level
R
Input
L
Group 1
Stereo
Group 2
Stereo
Group 3
L+R
– GR 2 –
– – GR 1+2
High Pass High Pass Low Pass
– – –
GTH400
GR 1
L– L+
R– R+
L–
GR 2
L+
R– R+
R
Rear
R
GR 2
L–
GR 3
R+
– + – + – + –
L R
Front Speakers
L R
Rear Speakers
Satellite Speakers
+ – +
Subwoofer
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GTH400-20107 06/03/98 15:49 Side 8
Application 3
4-Channel Full-Range or Bi-Amplified
4-Channel Full-Range
Group 1
Input Mode
Group 2 Input
Group 3 Input
Speaker Crossover
Preamp Output Crossover
L
–
–
Flat
–
Group 2
L
GR 2
–
Flat
–
Group 3
Stereo
–
GR 3
Flat
–
4-Channel Bi-Amplified with
Fading Mono Subwoofers
Group 1 Group 2
Input Mode
Group 2 Input
Group 3 Input
Speaker Crossover
Preamp Crossover
L
–
L
GR 2
Group 3
L+R
–
– – GR 3
High Pass High Pass Low Pass
– – –
*Stereo subwoofers may also be used by selecting “ST” on the group 3 input mode switch.
Note: Image Enhancement cannot be used in these applications.
Front
L
GR 1
L R L
Preamp or
Speaker-Level
L
Input
L
GR 2
R
Rear
R
GR 3
GTH400
GR 1
L– R+
GR 2
L– R+ L– L+
R–
GR 3
R+
– + – +
L
Front Speakers
R
– + – +
L R
Rear Speakers or Subwoofer
Application 4
3-Channel Bi-Amplified
4-Channel Input (Fading Subwoofer)
Input Mode
Group 2 Input
Group 3 Input
Speaker Crossover
Preamp Output Crossover
Group 1
L
–
Group 2
L
GR 2
Group 3
L+R
–
– – GR 3
High Pass High Pass Low Pass
– – –
L
Front
R
L
GR 1
2-Channel Input (Mono Subwoofer)
Input Mode
Group 2 Input
Group 3 Input
Speaker Crossover
Preamp Crossover
Group 1
L
–
–
Group 2
L
GR 2
–
Group 3
L+R
–
GR 1+2
High Pass High Pass Low Pass
– – –
Note: Image Enhancement cannot be used in these applications.
GTH400
GR 1
L– R+
GR 2
L– R+
L
Main Speakers
R
L
GR 2
L R
Rear
L
GR 3
R
Use these when
4-channel output is available.
L–
GR 3
R+
Subwoofer
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GTH400-20107 06/03/98 15:49 Side 9
4. Installation and Use
4.1 Controls and Connectors
1. Preamp-Level Input Connector –
Use these connectors for line (preamp) level 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. See “Audio Input
Connections” section (page 23) for wiring instructions. 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. See wiring directions for information on proper connections.
9. Fuses – Two 30 Amp ATC type fuses.
10. Gain Controls – Use these controls to adjust the gain of the amplifier channel group. See the “Adjusting the Gain” section (on page 25) 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 lowpass 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 bandpass 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
9
GTH400-20107 06/03/98 15:49 Side 10 to use in conjunction with a highpass filtered input signal to create a bandpass 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 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 L to drive both the left and right outputs with only a single input on the left 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 outputs.
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 effect 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.
16. Group 3 Input Switch – This switch is used to select which inputs will drive
Group 3 of the amplifier. Put the switch in position “GR 3” to allow
Group 3 to be driven by the Group 3 inputs. Put the switch in the “GR 2” position to drive Group 3 with the
Group 2 inputs. Put this switch in the
“GR 1+ 2” position to drive Group 3 with the sum of Group 1 and 2 for a
10 non-fading subwoofer output on
Group 3.
17. Remote Bypass/On Indicator – This indicator is on when the Imaging
Enhancer is engaged and off when the Imaging Enhancer is bypassed.
18. Driver/All Optimizer Indicator – This indicator is on when the Virtual Center
Channel circuitry is in “Driver” optimization mode and off when it is in the “All” passenger mode. Note: The enhancer on indicator must be on before driver’s mode can enabled.
19. Front Ambience Control and
On/Bypass Switch – Rotating this control adjusts the amount of ambience and front staging width produced by the Imaging Enhancer.
Pulling the knob places the Imaging
Enhancer in “Bypass” mode.
Pushing in the knob places the
Imaging Enhancer in “On” mode.
20. Rear Ambience and Driver/All
Optimizer Control – Rotating this knob controls the amount of rear-fill ambience and the “room size” of the acoustic environment when used in a system with rear speakers. Pulling the knob out places the Imaging
Enhancer in “All” passengers optimization mode. Pushing the knob in places the unit in “Driver” optimization mode. Best results at the driver’s position will be achieved with the control in the “Driver” setting.
17
19
IMAGING ENHANCER
ENHANCER ON
DRIVER MODE
FRONT AMBIENCE REAR AMBIENCE
ENHANCER
ON DRIVER
18
20
ALL BYPASS
MIN MAX MIN MAX
Power Indicator LED (on amp chassis
top) – LED steadily illuminates for normal operation. LED blinks when protection circuitry or muting is engaged.
GTH400-20107 06/03/98 15:49 Side 11
BASS BOOST BASS BOOST BASS BOOST
CH. 2 L OUT
CH. 1 R OUT
CH. 2 R OUT
CH. 2 R IN
CH. 2 L IN
CH. 1 R IN
CH. 1 L IN
CH. 1 L OUT
1 2
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GTH400-20107 06/03/98 15:49 Side 12
4.2 Internal Adjustments
Speaker-Level Input
Impedance Adjustments
The speaker level inputs of the GTH400 come factory set with 100k ohm input impedance. This will provide 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 practically nothing. On some older, or lower-priced head units, this load will not facilitate proper fader operation. To allow for this, we have provided the ability to change the input impedance of the speaker-level inputs to 15 ohms. This is accomplished by moving the jumpers
JUMPER SELECTOR
SELECT 100K OR 15 OHMS
150HMS
100K
150HMS
100K
INPUT
SELECTOR
150HMS
100K
150HMS
100K
PREAMP OUT
LINE INPUT shown on the diagram above. 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. For best results, a
Balanced Line Driver capable of at least
4V nominal output should be used.
If the head unit has 4 channels of builtin amplification and/or an electronic fader control, you should leave the jumpers in the factory set position.
If the head unit has 2 channels of amplification, with a speaker-level fader, the jumpers should be set to the
15-ohm position. This will always be a
12 rotary-type control, not one controlled by electronic pushbuttons.
If you are not certain of the type of fader control your unit has, measure the resistance across one set of speaker outputs with an ohmmeter (with the head-unit off). Adjust the fader control through its entire adjustment range. If there is a change in the resistance as the control is adjusted, set the jumpers to the 15-ohm position. (See step 1, page 16 to remove bottom cover.)
Crossover Frequency Adjustments
The GTH400 amplifiers include built-in frequency selectable crossovers. One crossover is connected in series with the amplifier circuitry and the other crossover is connected to the preamp level output jacks. These crossovers can be set in either the F (full bandwidth operation), L (subwoofer operation), or
H (satellite operation).
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.
Frequency Resistor JBL Part
Value Number
50Hz
80Hz
120Hz
200Hz
250Hz
375Hz
500Hz
650Hz
2.5kHz
5kHz
47k
Ω
33k
Ω
22k
Ω
12k
Ω
10k
Ω
6.8k
Ω
4.7k
Ω
3.9k
Ω
1k
Ω
470
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
GTH400-20107 06/03/98 15:49 Side 13
Custom Chip Construction
Regardless of whether you build or buy it, the necessary resistor network has the following configuration:
1. Remove the screws from the bottom panel as shown below.
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 recommended to remove the resistor chip. Pull the resistor chip from the socket as shown in the figure below.
•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 equation:
Resistor
Value in ohms
=
2,500,000
Frequency in Hz
•Use the following equation if you have a resistor pack of a known value, and want to find its crossover frequency:
Frequency in Hz
=
2,500,000
Resistor Value in ohms
•To build chips from discrete resistors, solder the resistors to a standard 14pin “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 1 ⁄
8
"-length, and insert them directly into the chip sockets.
To change the crossover frequency change the resistor network as follows:
JBL INC.
PC00108800
CROSSOVER
C13
HIGH PASS
FREQUENCY
C10
FILTER
SELECTION
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.
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.
Remote Chassis Installation
The wired remote of the GTH400 can be installed either in dash or under dash.
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GTH400-20107 06/03/98 15:49 Side 14
Under-Dash Remote Installation
1. Set the GTH400 remote in the installation location and mark two mounting screw hole locations.
2. Set the GTH400 remote aside and drill two pilot holes using a 1⁄16"-
(1mm) bit. Be careful not to drill into any of the car’s components.
3. Secure the spacer and faceplate
(with the control labeling) to the front of the remote control panel using the four smaller screws included.
4. Push the two adjustment knobs onto the metal shafts.
5. Set the GTH400 remote back in place and secure it using two sheet metal screws. Continue to Step 6 in the “In-Dash Installation” section.
In-Dash Remote Installation
1. Choose a location for the in-dash installation and use the template at the back of this manual to mark hole locations as shown on the template.
2. Drill the holes indicated on the template.
3. Using the diagram on page 15 as reference, install the remote behind the panel with the holes just drilled.
Position the remote so the two knobs feed through panel and the
LEDs are in alignment with the holes drilled.
4. Place the trim panel with the control labeling over the two shafts and secure it in place with the 4 screws provided.
5. Push the two adjustment knobs onto the metal shafts.
6. Connect one end of the GTH400
14 remote control wire (included) to the connector on the back of the remote control box.
7. Run the wire back to the GTH400 main chassis and plug the remote control wire into the “Remote In” connector on the main chassis.
Note: a standard 6-pin telephone extension cord may be used if more wire is needed for remote control connection. These extension cords can be purchased at many electronics or hardware stores.
In countries with Right Hand Drive vehicles, the built-in Image Enhancer will not operate properly with standard wiring. To use the GTH400 with right hand drive vehicles, reverse both the input and output wiring as shown below.
GTH400 Audio Signal Connection for Right Hand Drive Cars
GTH400
Rear
L
Front
R
Group 1
L R
Group 2
The right and left inputs and outputs of the GTH400 must be reversed for proper functioning of the virtual center image enhancer when used in a right hand drive automobile.
Power Supply Connections
The power input and remote turn-on wires are connected to the GTH400 via the power connector on the end of the amplifier.
+12V Battery Wire
•Connect a wire directly from the +12 volt terminal of the battery to the +
Battery terminal on the amplifier. Use a minimum of AWG #8. Use wire that
GTH400-20107 06/03/98 15:49 Side 15
FACE PLATE
FACE PLATE
DASH PANEL
SPACER
PLATE (INCLUDED)
Cassette/CD Tuner
Cassette/CD Tuner
Speaker Level Output Connection
(Use only when line level ouput is not available)
CD Player or Changer
Power
Antenna
Antenna Input
Cassette/Receiver
Power Supply
Wires
Power
Antenna
Relay
CD Input
Amplifier
Speaker
Level
Inputs
Cassette/CD Preamp Output
Amplifier
Power
Connection
Amplifier
Speaker
Output
Connection
Chassis Ground
Ignition Switch
–
Vehicle Battery
+
Blue w/White Stripe - Remote On/Off
IMAGING ENHANCER
60 Amp
(Not Included)
Fuse
Main +12V
Power Ground
+
–
Speakers
Amplifier
Speaker
Output
Connection
+
+
–
Speakers
Amplifier
Speaker
Output
Connection
+
+
–
Speakers
+
15
GTH400-20107 06/03/98 15:49 Side 16 is heat- and oil-resistant whenever running wires through the engine compartment. All wire-to-wire connections should be soldered and insulated with heat shrink tubing, or connected through a high-quality
Simultaneous Stereo-Mono
Connection Diagrams
A. Satellite/Subwoofer
Subwoofer (Low-Pass) insulated crimp-on connector or secure set-screw-type terminal blocks. Never leave bare wire exposed. Terminate wires with crimpor solder-on lug terminals whenever appropriate.
(–) (+)
High Pass Satellite
Crossover Frequency: 100Hz
C: 300
µ
F capacitor
100V, non-polorized
Subwoofer Lowpass
Crossover Frequency: 100Hz
L: 6.2mH air core inductor
(–)
Tweeter/Midrange Satellites
Left
(High Pass)
(+)
C
L
(+)
C
Right
(–)
GTH400
R
L
B. Center Channel
1
LINE LEVEL INPUTS
2 3 1
PREAMP OUTPUTS
2 3
SPEAKER LEVEL
INPUTS
R 2 L
+ – – +
+
L 1 R
+ +
SPEAKER OUTPUTS
L 2 R
+ +
L 3 R
+
FUSE
30A
FUSE
30A
REM IN
POWER
REM OUT
+
–
+ – – +
R 1 L
_ _ _ _ BATT(+)
*You may change the subwoofer satellite crossover frequency by using the
Inductor and Capacitor values calculated with the following formulas:
GND
30,000
Desired crossover Frequency in Hz
µ
F
620
Desired crossover Frequency in Hz
Center Channel
Bridged Speaker Connection*
(–)
8
Ω
Minimum
(+)
8
Ω
L-Pad
(Optional but Recommended)
GTH400
L
R
1
LINE LEVEL INPUTS
2 3 1
PREAMP OUTPUTS
2 3
SPEAKER LEVEL
INPUTS
R 2 L
+ – – +
+
L 1 R
+ +
SPEAKER OUTPUTS
L 2 R
+ +
L 3 R
+
FUSE
30A
FUSE
30A
REM IN
POWER
REM OUT
+ – – +
R 1 L
+
–
_ _ _ _
BATT(+) GND
* Center Channel Speaker Minimum 8 Ohms, Main
Speakers Minimum 4 Ohms When Used Simultaneously.
Stereo, Non-Bridged
Speaker Connection*
(+)
4
Ω
Minimum
(–) (–)
4
Ω
Minimum
(+)
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GTH400-20107 06/03/98 15:49 Side 17
•The GTH400 will draw as much as 60 amps from the vehicle’s electrical system, enough to overload conventional vehicle wiring. Therefore the +12 volt power supply must be taken directly from the positive side of the battery.
Do not connect to the vehicle’s fuse block or to a wire feeding other accessories.
•To prevent electrical system damage or fire, a fuse holder and fuse (not included – maximum 60 Amp) must be installed in the power supply wire as close to the battery as possible, and before the wire travels through the firewall or other metal panel.
Ground Wire
•Proper grounding is extremely important. Use a heat- and oilresistant 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.
The color code for the speaker-level input harness is as follows:
Speaker-Level Input Harness
Color Codes
Group 1 Left (+):
Group 1 Left (–):
White
White with
Black Stripe
Group 1 Right (+): Gray
Group 1 Right (–): Gray with
Black Stripe
Group 2 Left (+):
Group 2 Left (–):
Green
Green with
Black Stripe
Group 2 Right (+): Purple
Group 2 Right (–): Purple with
Black Stripe
5. Adjusting the Gain
Before operating the GTH400, recheck all wiring connections to make sure they are correct and secure. Be sure that a fuse (60 amps, not included) is installed in the +12V line near the battery.
Reconnect the negative ground (–) terminal of the battery. Make sure that the mode switches, crossover switches,
Group 2 & 3 Input switches, and crossover frequency modules, are properly set.
•The setting of the gain controls on the
GTH400 is important to ensure proper performance, low noise levels, and maximum reliability in the system. As a general rule, controls on components at the front-end of the system (source, equalizers, electronic crossovers, etc.) should be set as high as possible, with the amplifier gain control set as low as possible while still providing adequate volume levels. Using a high signal level from the source and a low gain setting on the amplifier will help keep
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GTH400-20107 06/03/98 15:49 Side 18 background noise levels in the system low.
•To adjust a system using a single
GTH400, start with all three of the amplifier gain controls fully counterclockwise and the Imaging
Enhancer Remote set to “Bypass” mode. Some head units have additional output level controls or switches. Set those to their maximum position.
•Set the level controls on any associated equipment such as equalizers and electronic crossovers as recommended by their manufacturers. 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. This is the maximum undistorted output level of your head unit and signal processors, and should not be exceeded during use. If audible distortion does not occur, continue to increase the level until the head unit is turned all the way up. If this setting does not provide adequate volume levels, gradually increase (turn clockwise) the gain control for the main (usually front) speaker groups on the GTH400 until the system plays as loud as necessary or when the first signs of distortion are heard.
•After adjusting the main speaker’s gain control, you may then turn down
18 the head unit’s volume control to a comfortable level, and adjust the remaining channels for the desired system balance. You will find this easiest to do by adjusting the channels in the following order: 1) front speaker Group, 2) rear speaker
Group, 3) subwoofer speaker Group.
Elaborate systems incorporating tri- or quad-amplification can be complex to adjust. Your local authorized JBL installation specialist is the best person to help with such adjustment.
Imaging Enhancer Setup
After the installation and set up is finished and all wiring is checked, proceed with the next few steps to set up the Imaging Enhancer on the
GTH400.
Note: Since the Imaging Enhancer in the GTH400 is primarily designed to optimize the sound stage for the driver, all tests should be performed while sitting in the driver’s seat.
1.
The Power Indicator LED on the
GTH400 main chassis should light up when the head unit is turned on.
2.
Make sure the “Front-Ambience/
Bypass/On” knob and “Rear-
Ambience/Driver/All” knobs are pushed in and rotated completely counterclockwise.
3.
Play a selection which has vocals and good “center” information.
4.
Gently turn up the volume to a comfortable listening level. You should hear a very distinctive center image coming from the middle of your dashboard. If not, make sure the “Rear-Ambience/Driver/All” knob is pushed in to the “Driver”
GTH400-20107 06/03/98 15:50 Side 19 position for driver-optimized sound stage.
5.
Proceed to push and pull the Rear-
Ambience knob to hear the effects of “Driver” and “All” modes. You should hear imaging coming from the middle of the dashboard when the knob is pushed in (“Driver” mode). You should hear stereo with ambience recovery when the knob is pulled out (“All” mode). If you find that the center imaging in the
“Driver” position is slightly offset to the left or right side of the dashboard, switch the car-size switch located inside of the
GTH400 under the bottom cover as shown below. This switch optimizes the Imaging Enhancer for standard or large cars.
IMAGING ENHANCER
REMOTE PLUG
FRONT
PLATE
Imaging Enhancer
Car Size Switch
IMAGE
ENHANCER
MODULE
Standard Large
6.
Slowly turn the “Front-Ambience” knob in the clockwise direction to increase ambience. You should begin to hear slight reverberation in the music and a sense of a widening front sound stage in both the “Driver” and “All” modes.
7.
Slowly turn the “Rear-Ambience” knob in the clockwise direction to increase rear ambience (only in systems with rear speakers). You should begin to hear an increase in reverberation and get a feeling of being in a very large auditorium.
Note: The GTH400 converts the rear channels into true rear-fill surround channels which cancel all center information (vocals, lead instruments, etc.) and lets only true ambience information come out.
This same process is used in more expensive “Surround Sound” systems used in theaters.
8.
Adjust the front and rear ambience as desired. For optimum center imaging, it is recommended that ambience be used sparingly on the front channels.
9.
To bypass the effects of the
Imaging Enhancer in the GTH400, simply pull on the “Front-
Ambience” knob until it clicks to the
“Bypass” position. The “Enhancer
On” LED on the remote control panel will turn off and your sound system should revert back to normal stereo sound without ambience enhancement. The
Imaging Enhancer is also bypassed when the remote control is unplugged from the amplifier.
6. Important Characteristics
Overload Protection – The GTH400 incorporates elaborate protection circuitry to prevent damage to the amplifier circuitry and ensure reliable operation. This circuitry will turn the amplifier off in the event of overheating, a short circuit on the speaker output wiring, or improper power supply connections. If the amplifier cycles on
19
GTH400-20107 06/03/98 15:50 Side 20 and off, or does not work at all, a problem in installation or an abnormal electrical condition is indicated. Check speaker wiring for short circuits or impedance loads significantly below 2 ohms (4 ohms in bridged mode). Check the power supply voltage at the input of the amplifier to be sure that it is normal; between 11 and 16 volts. Check that the power wires are not reversed.
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GTH400-20107 06/03/98 15:50 Side 21
7. 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 defective; check for continuity with an ohmmeter between the amplifier’s ground terminal and a known chassis ground point.
• Battery wire is disconnected or defective; check for approximately +12 volts 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 an identical one. If the new fuses blow immediately, then check all the wiring connections. If no fault is found, consult your JBL dealer.
• Remote-on wire between the head unit and the amplifiers is disconnected or defective; check for +12 volts between amplifiers remote-on input terminal and the ground wire with the head unit on.
Power light is on, but no sound is heard • Incorrect switch settings; make sure from some or all of the speakers that all switches (mode, input and crossover) are in their correct positions for your system configuration.
• Incorrectly connected or shorted speaker wires; check for shorts in wiring.
• Defective or disconnected audio cables; check for continuity and replace if necessary.
• Incorrect gain adjustment; verify that the amplifier gain controls are not turned completely down. If they are, sound output level may be very low and may give the impression that the system (or part of the system) is dead.
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GTH400-20107 06/03/98 15:50 Side 22
Power light is on, but no sound is heard from some or all of the speakers
Power light is blinking and no sound is heard
• Defective head unit or signal processor; check each component for proper wiring and operation.
• Defective GTH400; If there is audio signal present at the inputs of the amplifier and there is no output, the
GTH400 may be defective.
Alternator whine through the audio system • Ground loops; follow the wiring with the engine running suggestions 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.
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).
Amplifier Power Light is on and sound is heard from the front and rear channels but the Imaging is not improved with the image enhancer on
• Verify that the remote control is not set in “BYPASS” mode by checking to see that the “ON” LED is lit.
• Using the system configuration diagram, confirm that the audio connections are correct for signal path and polarity. Note that right hand drive car installations must have the Left and Right input and output connections reversed as shown in the wiring section on page 19.
• Perform the adjustments as directed in the Imaging Enhancer Setup section.
• Incorrectly connected or shorted speaker wires; check for shorts in wiring.
• Defective GTH400; if there is no short on the speaker outputs, the GTH400 may be broken. Consult your JBL dealer.
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GTH400-20107 06/03/98 15:50 Side 23
8. Specifications
Signal to Noise Ratio
Frequency Response
GTH400
35 Watts x 4 + 70 Watts x 2 (4 ohms, 0.05% THD)
50 Watts x 4 + 100 Watts x 2 (2 ohms, 0.08% THD)
100 Watts x 2 (Bridged 4 ohms, 0.08% THD) +
70 Watts x 2 (4 ohms, 0.05% THD)
100 Watts x 2 (Bridged 4 ohms, 0.08% THD) +
200 Watts x 1 (Bridged 4 ohms, at 0.08% THD)
100dBA
10Hz – 50kHz (+0, –1dB)
20Hz – 20kHz (+0, –0.1dB)
Damping Factor
Slew Factor
Line Level Input Sensitivity
(For Rated Power)
Line Level Input Impedance
Speaker Level Input Impedance
>200
>5
100mV – 4V RMS
10k ohms
15 ohm or 100k ohm
(Selectable by Internal Jumpers)
200mV – 8V RMS Speaker Level Input Sensitivity
Preamp Output Sensitivity
Preamp Input:
Speaker Input:
Minimum Speaker Impedance
Single Ended (Non-Bridged)
4V in for 4V out
4V in for 2V out
2 ohms
Bridged 4 ohms
Built-in Electronic 18dB per Octave Low-Pass Filter,
Crossover Frequency and Slope Frequency Chips Available from 50–5kHz
Factory Setting 80Hz
Bass Boost Frequency and Magnitude
18dB per Octave High-Pass Filter,
Frequency Chips Available from 50–5kHz
+4dB at 40Hz
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GTH400-20107 06/03/98 15:50 Side 24
Power Requirement
Fuse Size
Size (L x W x H)
Weight
Speaker Level Input
Mating Connector
11 to 16V DC Negative Ground
30 Amp ATC Type Fuse (2 per Amplifier)
15-1/4" x 11-1/4" x 2" (387mm x 286mm x 51mm)
13 lbs 4 oz (6 kg)
Molex Mini-Fit Jr
#39-01-2080
Metal Pins: 39-00-0038
24
UP
Remote Control Drilling Template
9/64" (3.5mm) in 4 places
9/64" (3.5mm) in 2 places
UP
25/64" (10mm) drill in 2 places
GTH400-20107 06/03/98 15:50 Side 25
Staple or clip your original bill of sale here. ▼
25
