User manual JBL GTQ200

[. . . ] The GTQ200 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 GTQ200 and GTQ240 feature JBL's Universal InterfaceTM design, which facilitates simple connection to factory radios with the low distortion that is usually only associated with preamp level connection. [. . . ] 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 GTQ200 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 4. Wiring 4. 1 Wiring 3. 2 Signal Sources The low-level preamp outputs of any radio/tape deck, CD player, or preamp/ equalizer so equipped can drive the GTQ200 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. Thanks to Universal Interface Circuitry, the GTQ200 or GTQ240 can also be connected to power amplifiers, radios or equalizers that are equipped with only speaker outputs by connecting them through the speaker-level input connector. Inside the GTQ200 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 control, may be connected to the preamplevel inputs at the same time as a powered radio/tape unit is connected to the speaker-level inputs. This provides a higher performance alternative to an FM modulator connection when you wish to add CD capability to a factory cassette stereo. This will always be a rotary-type control, not one controlled by electronic pushbuttons. JUMPER SELECTOR SELECT 100K OR 15 OHMS 5. 2 Crossover Frequency Adjustments The GTQ 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). 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 listed 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 resistors mounted on a 14-pin DIP Header using the instructions which follow. 5. 3 Custom Chip Construction Regardless of whether you build or buy it, the necessary resistor network has the following configuration: 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 operation mode with either a ground or nothing 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 equation: 4. 5 Speaker-Level Input Harness Color Codes Group 1 Left (+): Group 1 Left (­): Group 1 Right (+): Group 1 Right (­): Group 2 Left (+): Group 2 Left (­): Group 2 Right (+): Group 2 Right (­): White White with Black Stripe Gray Gray with Black Stripe Green Green with Black Stripe Purple Purple with Black Stripe Resistor Value = in ohms 2, 500, 000 Frequency in Hz Frequency 50Hz 80Hz 120Hz 200Hz 250Hz 375Hz 500Hz 650Hz 2. 5kHz 5kHz Resistor Value 47k 33k 22k 12k 10k 6. 8k 4. 7k 3. 9k 1k 470 JBL Part Number 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 · Use the following equation if you have a resistor pack of a known value, and want to find its crossover frequency: 2, 500, 000 Frequency = Resistor Value in ohms in Hz · 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. 100K 15 LI NE IN PU T T BA 30 30 D GN M RE T OU 7 BEST-Vertical Mounting To change the crossover frequency change the resistor network as follows: 1. [. . . ] · Remote-on wire between the head unit and the amplifiers is disconnected or defective; check for +12 volts between amplifier's remote-on input terminal and the ground wire with the head unit on. 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 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. [. . . ]