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GTH400-20107 06/03/98 15:49 Side 26
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GTH400-20107 06/03/98 15:49 Side 1 GTH400 6/5/4/3 CHANNEL AUTOMOTIVE POWER AMPLIFIER OWNER’S MANUAL GTH400
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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.............
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GTH400-20107 06/03/98 15:49 Side 3 In addition to conventional preamp- 1. Introduction level inputs, the GTH400 features JBL’s Thanks for purchasing your new GT Universal Interface design, which series automotive multichannel ampli- facilitates simple connection to factory fier. Your GT series amplifier will easily radios with the low distortion that is connect to virtually any car audio usually only associated with preamp system, whether it is factory installed or level connection. In additio
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GTH400-20107 06/03/98 15:49 Side 4 1.1 Features 1.2 About Installation Theory of Operation – Although the GTH400 is designed to Virtual Center Image Enhancer make installation as easy as possible, it is an extremely sophisticated product JBL’s breakthrough “Virtual Center” that requires proper installation and circuitry is the result of the setup to realize its full performance understanding of how the human ear potential. If you feel you do not have responds to timing, frequency, and the nece
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GTH400-20107 06/03/98 15:49 Side 5 6. Connect the outputs from the head 2. Installation and use unit to the appropriate inputs of the Refer to the “Crossover Frequency amplifier according to the Wiring Adjustments” and “Speaker-Level Input Diagram (page 18) with either (or Impedance Adjustments” sections of both) high quality low-level signal this manual to see if you will need to cables with RCA plugs, or the make alterations to their factory supplied speaker-level input settings. connector.
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GTH400-20107 06/03/98 15:49 Side 6 When a group of the GTH400 is in 3. System Design Using bridged mode, the combined the GTH400 impedance of the speaker (or speakers) 3.1 Speaker Requirements connected to the bridged channels When used in the non-bridged mode a should be at least 4 ohms. As in the group-channel of the GTH400 can example above, sustained operation of easily drive two 2-ohm speaker loads. the GTH400 in bridged mode with less When only one speaker is connected to than 4 ohms wi
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GTH400-20107 06/03/98 15:49 Side 7 3.2 Typical Applications The GTH400 uses the terminology “Group 1,” “Group 2” and “Group 3” to The diagrams on pages 8 & 9 show indicate the three main signal paths the most common basic system within the amplifier. Each “group” may configurations of the GTH400. One consist of a mono bridged signal or a or more of these building blocks may stereo pair of L+R signals depending be combined to form elaborate system on the system configuration. designs. Applic
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GTH400-20107 06/03/98 15:49 Side 8 Application 3 4-Channel Full-Range or Bi-Amplified L R L R Preamp or Front Rear 4-Channel Full-Range Speaker-Level Input Group 1 Group 2 Group 3 L L L R Input Mode L L Stereo GR 1 GR 2 GR 3 Group 2 Input – GR 2 – Group 3 Input – – GR 3 Speaker Crossover Flat Flat Flat Preamp Output Crossover – – – GTH400 4-Channel Bi-Amplified with GR 1 GR 2 GR 3 L– R+ L– R+ L– L+ Fading Mono Subwoofers R– R+ Group 1 Group 2 Group 3 Input Mode L L L+R Group 2 Input – GR 2 –
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GTH400-20107 06/03/98 15:49 Side 9 10. Gain Controls – Use these controls 4. Installation and Use to adjust the gain of the amplifier 4.1 Controls and Connectors channel group. See the “Adjusting 1. Preamp-Level Input Connector – the Gain” section (on page 25) for Use these connectors for line (pre- tips on proper setup. amp) level inputs to the amplifier. 11. Preamp Crossover Switches – These 2. Preamp-Level Output Connector – switches control the built-in cross- Use these outputs to send ov
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GTH400-20107 06/03/98 15:49 Side 10 to use in conjunction with a high- non-fading subwoofer output on pass filtered input signal to create a Group 3. bandpass crossover (for a midrange 17. Remote Bypass/On Indicator – This or midbass driver). Set the switch to indicator is on when the Imaging H (high) to activate the high-pass Enhancer is engaged and off when filter for use with satellite speakers or the Imaging Enhancer is bypassed. tweeters on an amplifier group. 18. Driver/All Optimizer Ind
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GTH400-20107 06/03/98 15:49 Side 11 ‚ ‚ ‚ • • • ‚ ¶ ¶ ¶ • ¶ 11 GTH400 Block Diagram IMAGE GR 1 MODE SWITCH ENH. Preamp-level inputs 1 1 1 2 LP 2 1 + L X-OVER 3 3 2 2 AMP GR 1 Left Speaker Out Buffer ∑ Buffer 3 HP GR 1 L 3 PREOUT GR 1 1 1 1 1 2 + 3 2 LP AMP GR 1 Right Speaker Out Buffer ∑ 2 3 R X-OVER 2 GR 1 R Buffer 1 3 PREOUT HP 3 2 + L Buffer ∑ 1 1 1 1 2 2 LP AMP GR 2 Left Speaker Out 1 2 2 Buffer 2 X-OVER 3 GR 2 3 3 3 GR 2 L HP PREOUT + GROUP 2 INPUT Buffer ∑ 1 R 1 – GR 1 2 – GR 2 2 1 1 B
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LINE INPUT PREAMP OUT GTH400-20107 06/03/98 15:49 Side 12 4.2 Internal Adjustments rotary-type control, not one controlled by electronic pushbuttons. Speaker-Level Input Impedance Adjustments If you are not certain of the type of fader control your unit has, measure the The speaker level inputs of the GTH400 resistance across one set of speaker come factory set with 100k ohm input outputs with an ohmmeter (with the impedance. This will provide the lowest head-unit off). Adjust the fader contro
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GTH400-20107 06/03/98 15:49 Side 13 Custom Chip Construction 1. Remove the screws from the bottom panel as shown below. Regardless of whether you build or buy it, the necessary resistor network has the following configuration: 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 •Each resistor in the p
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GTH400-20107 06/03/98 15:49 Side 14 Under-Dash Remote Installation remote control wire (included) to the connector on the back of the 1. Set the GTH400 remote in the remote control box. installation location and mark two 7. Run the wire back to the GTH400 mounting screw hole locations. main chassis and plug the remote 2. Set the GTH400 remote aside and control wire into the “Remote In” drill two pilot holes using a 1⁄16"- connector on the main chassis. (1mm) bit. Be careful not to drill into
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GTH400-20107 06/03/98 15:49 Side 15 FACE PLATE DASH PANEL FACE PLATE SPACER PLATE (INCLUDED) Cassette/CD Tuner Speaker Level Output Connection (Use only when line level ouput is not available) CD Player Cassette/CD Tuner or Changer Antenna Input CD Input Amplifier Power Speaker Cassette/Receiver Antenna Power Supply Level Inputs Wires Power Amplifier Amplifier Power Antenna Cassette/CD Preamp Output Speaker Connection Relay Output Connection + – Speakers Blue w/White Stripe - Remote On/Off Am
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30A 30A 30A 30A GTH400-20107 06/03/98 15:49 Side 16 is heat- and oil-resistant whenever insulated crimp-on connector or running wires through the engine secure set-screw-type terminal compartment. All wire-to-wire blocks. Never leave bare wire connections should be soldered and exposed. Terminate wires with crimp- insulated with heat shrink tubing, or or solder-on lug terminals whenever connected through a high-quality appropriate. Simultaneous Stereo-Mono Connection Diagrams Subwoofer (Low-P
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GTH400-20107 06/03/98 15:49 Side 17 •The GTH400 will draw as much as 60 Speaker-Level Input Harness amps from the vehicle’s electrical Color Codes system, enough to overload Group 1 Left (+): White conventional vehicle wiring. Therefore Group 1 Left (–): White with the +12 volt power supply must be Black Stripe taken directly from the positive side of the battery. Group 1 Right (+): Gray Do not connect to the vehicle’s fuse Group 1 Right (–): Gray with block or to a wire feeding other Black
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GTH400-20107 06/03/98 15:49 Side 18 background noise levels in the system the head unit’s volume control to a low. comfortable level, and adjust the remaining channels for the desired •To adjust a system using a single system balance. You will find this GTH400, start with all three of the easiest to do by adjusting the amplifier gain controls fully channels in the following order: 1) counterclockwise and the Imaging front speaker Group, 2) rear speaker Enhancer Remote set to “Bypass” Group, 3)
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GTH400-20107 06/03/98 15:50 Side 19 position for driver-optimized sound systems with rear speakers). You stage. should begin to hear an increase in reverberation and get a feeling of 5. Proceed to push and pull the Rear- being in a very large auditorium. Ambience knob to hear the effects Note: The GTH400 converts the of “Driver” and “All” modes. You rear channels into true rear-fill should hear imaging coming from surround channels which cancel the middle of the dashboard when all center inf
