GT-28 GT-24 2-Channel, High-Current/High-Power Amplifiers Table of Contents Parts List Features and Specifications Control Functions Control functions (cont.) 3 3 4 5 Mechanical Functions Recessed RCA inputs Control cover removal and reinstallation Multi-position mounting feet Vents (side and rear) Mechanical functions (cont.) Amplifier linking Wire connection Fuses 6 6 6 6 6 7 7 7 7 General Installation Precautions Before you install Battery and charging system Wire routing 8 8 8 8 Installation--Amplifier Mounting Choose the mounting location Height, width, and depth diagrams Installation--amplifier mounting (cont.) Passenger & trunk compartment mounting 9 9 9 10 10 Installation--Fuses and Wiring Amplifier fuses Wire gauge Installation--fuses and wiring (cont.) Power/B+ and power/ground (GND) connection Remote input connection Speaker output connection Installation--fuses and wiring (cont.) Mono subwoofer operation 10 10 10 11 11 11 11 12 12 Setup Tuning--Full-Range Speakers Music Sensitivity controls Highpass and lowpass crossover controls Setup tuning--full-range speakers (cont.) Head unit Volume Input sensitivity control Crossover controls Setup tuning--full-range speakers (cont.) "Q" control 12 12 12 12 13 13 13 13 13 14 14 Setup Tuning--Rear Fill Speakers Setup Tuning--Subwoofers Input switch Setup tuning--subwoofers (cont.) Head unit Volume Input sensitivity control Lowpass crossover control Phase 14 14 14 15 15 15 15 15 15 System Examples Amplifier Troubleshooting Guide Contact and Warranty Information 2 16,17 18 19 Parts List Included Hardware: GT-28 & GT-24 (1) owner's manual (1) female quick-connect terminal for remote input (1) 2mm hex wrench (for speaker input) (1) 3mm hex wrench (for power input) (6) mounting screws Features and Specifications GT-28 and GT-24 Features 2-Channel, High-Current Amplifier 2 Mono Operation Power Increase with Input Voltage Rise Advanced Cooling Allows Varied Mounting Positions Adjustable Feet for Varied Mounting Surfaces 24dB or 12dB Octave Lowpass Setting Continuously Variable Crossover and Q-factor Settings Selectable Highpass, Lowpass, and Bandpass Settings Bandpass Configurable for Midbass or Subwoofer Terminals Accept Bare, Heavy-Gauge Wire Screw-Down Security Cover Protects Tuning Controls Optional Remote Subwoofer Level Control Technical Specifications GT-28 14.4VDC Power @ 4 Ohms @ 2 Ohms @ 4 Ohms (mono) @ 2 Ohms (mono) 12.6VDC Power @ 4 Ohms @ 2 Ohms @ 4 Ohms (mono) @ 2 Ohms (mono) Frequency Response (-3dB) Signal-to-Noise Ratio (A Weighted) Dimensions (HxWxD) 2x250W 2x450W 1x900W 1x1350W GT-24 2x175W 2x275W 1x550W 1x900W 2x200W 2x350W 1x700W 1x1100W 10Hz­95kHz >100dB 21/4x215/8x8 7/8" (57x548x225mm) 2x120W 2x200W 1x440W 1x750W 10Hz­95kHz >100dB 21/4x18x8 7/8" (57x458x225mm) 3 Control Functions 3 STEREO INPUT MONO L OFF 9 ON SUBWOOFER LEVEL 7 OFF L OW PA S S S L O P E 1 2 d B 12dB 2 4 d B MONO ST 6 ON L OW PA S S OFF 5 ON HI GHPAS S FUSE 4 x 25A 350 200 Hz 350 185 Hz 50 0 .2 I NP UT S E NS I T I V I T Y I N PUT REMOTE SUBWOOFER LEVEL 20 MONO 1 .2 0 .9 5 Q/HP L R B+ B+ GND GND 2 .6 5 0.7 SPEAKER OUTPUT 12.6­14.4VDC GROUND 4 8 GT-28 Top Panel Shown 1 STATUS M O NO 12.6­14.4VDC GROUND 9 2 B+ B+ GND GND L R ON SAF E 10 GT-28 Front Panel Shown 1 RCA Inputs RCA cables from head unit or from other line level device should be connected here. Use both inputs (L and R) for stereo; use "L" input for mono. 1 2 2 Remote Input Use the supplied FEMALE quick-connector to connect the REMOTE trigger lead from the head unit to the amplifier. Amplifier turns "ON" when head unit is turned "ON." One FEMALE .210" connector is supplied with amplifier. 3 Input Switch In the left position, the L and R inputs go to the L and R channels of the amplifier. In the right position, the input is for mono operation. ST ER EO I N PU T M O NO L 4 Input Sensitivity Control Turn control clockwise to increase the amplifier sensitivity to incoming signals. Turn control counterclockwise to decrease the amplifier sensitivity. 0.2 INPUT SENSITIVITY 2. 6 5 5 Highpass Crossover Controls To use 12dB/octave crossover, move HIGHPASS switch to right-hand position. Highpass crossover frequency is adjustable from 20Hz to 350Hz by rotary control. (Moving switch to left-hand position will bypass crossover functions.) OFF HI G HPAS S ON 350 185 Hz 20 4 Control Functions (cont.) 6 Lowpass Crossover Controls To use lowpass crossover move LOWPASS switch to righthand position. Lowpass crossover frequency is adjustable from 50Hz to 350Hz by rotary control. (Moving switch to left-hand position will bypass crossover functions.) OFF L OWPASS ON 350 200 Hz 50 7 Lowpass Slope Select appropriate crossover slope of 12 or 24dB/octave by moving LOWPASS SLOPE switch. L OW PA SS SL O PE 12d B 12d B 24d B MONO ST 8 "Q" Control The "Q" Control is active when the highpass crossover is engaged and is centered on the selected crossover point. The range of operation is 0.7­1.2. dB Q +1.6dB 0dB -3dB .707 .95 1.2 t (tuned crossover frequency) 9 Subwoofer Level Control Port SUBWOOFER LEVEL switch should be set to "OFF" when control circuit is not installed, (see optional Subwoofer Level Control owners manual). 10 Status LED Indicators GREEN indicates the normal operating condition; the amplifier is "ON." GREEN and RED together are normal when the amplifier is first turned "ON"; RED will turn off after a few seconds. When both GREEN and RED remain on, the amplifier is in thermal shutdown condition. RED only indicates a fault condition, "SAFE." 5 Mechanical Functions Recessed RCA Inputs The input jacks are recessed into the body of the amplifier to provide clearance in tight mounting locations. 1 inch 1 inch Control Cover Removal and Reinstallation The cover panel is secured with two (2) captive coin-slotted screws. Coin-slotted screws allow a coin edge to be used as a screwdriver to remove the panel. Multi-Position Mounting Feet The mounting feet are designed to slide in both directions to clear installation obstructions on the mounting surface. WARNING! Before driving the mounting screws through any surface, be sure of what is behind that surface. Check for the gas tank, brake lines, and any vehicle wiring harness. Vents (Side and Rear) The cooling vents must be kept clear of obstructions once the amplifier is installed. Failure to do this could lead to premature thermal shutdown or amplifier failure. upper side vent lower side vent 6 Mechanical Functions (cont.) Amplifier Linking The design of the side panels enables multiple amplifiers to be used together without additional hardware. Wire Connection Amplifier accepts stripped wire directly into the terminal blocks. Speaker outputs accept 8-gauge, and the DC power and ground accept 4-gauge. Tighten with supplied hex wrenches. Fuses Amplifier accepts standard AT-style automotive blade fuses. FUSE 4 x 25A FUSE 3 x 20A GT-28 GT-24 7 General Installation Precautions WARNING! Before driving the amplifier mounting screws through any surface, be sure of what is behind that surface. Check for the gas tank, brake lines, and any vehicle wiring harness. Never run wires outside or under the vehicle or where they could become broken or interfere with the safe operation of the vehicle. Before You Install Before you install the unit, disconnect the negative (­) battery cable in the engine compartment of the vehicle. Doing so will prevent damage to both the electrical system of the vehicle and the amplifier during installation. Battery and Charging System In order for the amplifier to function correctly, the electrical system of the vehicle should be professionally checked for overall electrical capacity. When used, the amplifier will increase the demand on the battery and alternator. Therefore, both should be thoroughly evaluated before installing the amplifier to ensure they are in normal operating condition and able to handle the increased demand the amplifier will present to the vehicle's electrical system. Wire Routing Do not run the power wire near any low-level signals or audio cables such as the RCAs from the head unit. (Noise can be introduced into the amplifier when this occurs.) It is helpful to diagram the wire layout first before any installation is attempted. 8 Installation--Amplifier Mounting Choose the Mounting Location Plan your installation so that the amplifier is mounted where adequate ventilation is available. Never mount an amplifier in the engine compartment of a vehicle! WARNING! Before driving the mounting screws through any surface, be sure of what is behind that surface. Check for gas tank, brake lines, and any vehicle wiring harness. 13mm (1/2") 225mm (87/8") GT-28 (GT-24 depth dimensions are the same) GT-28 57mm (21/2") GT-24 57mm (21/2") 458mm (18") 548mm (215/8") 9 Installation--Amplifier Mounting (cont.) Passenger and Trunk Compartment Mounting If the amplifier is mounted under a seat, be sure that the vents do not become blocked. Do not allow seat padding or other obstructive material to press down on the amplifier. All Boston GT amplifiers have top panel controls. If the amplifier is mounted under a seat, position the amplifier so the cover panel can be removed with the seat forward or back to allow adjustment of the audio settings. When mounting in a trunk, choose a location that will be protected from sliding cargo or other materials. Mount the amplifier to solid surfaces only. Do not mount to plastic trim panels. Do not mount the amplifier with Velcro, doublestick tape, or by wedging into position. Amplifier should be mounted using the movable mounting feet and the provided mounting screws. Installation--Fuses and Wiring Amplifier Fuses Although the amplifier has internal fuses, additional fusing should be provided at the battery on the positive (+) power wire going to the amplifier. An inline fuse should be installed at no more than 18" (46cm) on the positive (+) power wire. The rating of the inline fuse should equal the value of the internal fuses of the amplifier if only the amplifier is connected to this wire. If other devices are connected to this wire, the fuse value should be of sufficient capacity to handle the demand. FUSE 4 x 25A GT-28 FUSE 3 x 20A GT-24 Wire Gauge The amplifier accepts up to 4-gauge stripped wire at the DC power and ground input terminals, and 4-gauge is recommended. Wire runs should be kept to the minimum practical length. 10 Installation--Fuses and Wiring (cont.) Power/B+ and Power/GND Connection Strip approximately 5/8" (16mm) of insulation. The positive (+) power wire is installed into the amplifier terminal marked "B+". The negative (­) wire is installed into the terminal marked "GND". The ground wire should be as short as possible and connected directly to the chassis of the vehicle. Make sure that the chassis connection point is free of rust, grease, dirt, paint, and other materials that may insulate the ground wire from making proper connection. Tighten the B+ and GND terminals with the supplied 3mm hex wrench to secure the wire into the terminals. If the power wire must be routed through a drilled or existing hole, use a nylon panel grommet to prevent fraying the wire insulation. Failure to do so could lead to an electrical short if the wire insulation is worn through and the power wire is shorted to ground. 1/ " 4 Strip 5/8" (16mm) Remote Input Connection Use the supplied FEMALE quick-connector to connect the REMOTE trigger lead from the head unit to the amplifier. Crimp connector to wire from head unit that controls remote turn-on (refer to head unit owner's manual). Once the quick-connector is crimped into place, carefully push connector onto recessed MALE REMOTE terminal adjacent to the RCA input pair. Only one (1) remote turn-on terminal should be connected. Speaker Output Connection Prepare each wire by stripping approximately 5/8" (16mm) of insulation. The positive (+) speaker wires are installed into the amplifier terminals marked "SPEAKER OUTPUT" / "+". The negative (­) speaker wires are installed into the amplifier terminals marked "SPEAKER OUTPUT" / "-". Tighten the "SPEAKER OUTPUT", "+", and "-" terminals with the supplied 2mm hex wrench to secure the wires into the terminals. If the speaker wires must be routed through a drilled or existing hole, use a nylon panel grommet to prevent fraying the wire insulation. Failure to do so could lead to an electrical short if the wire insulation is worn through and the speaker wires are shorted to ground. MONO L R SPEA K ER O U TPU T 11 Installation--Fuses and Wiring (cont.) Mono Subwoofer Operation When the amplifier is configured for mono operation, use the speaker output terminals marked for mono use. WARNING! Subwoofer impedance must not fall below 2 ohms when in MONO mode. 2-ohm minimum MONO L R SPEAKER OUTPUT Setup Tuning--Full-range Speakers 1) Music The material chosen for head ...