Boston Acoustics GT-28, GT-24 User Manual

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GT-28GT-24

2-Channel,High-Current/High-PowerAmplifiers

Table of Contents

Parts List

3

Features and Specifications

3

Control Functions

4

Control functions (cont.)

5

Mechanical Functions

6

Recessed RCA inputs

6

Control cover removal and reinstallation

6

Multi-positionmounting feet

6

Vents (side and rear)

6

Mechanical functions (cont.)

7

Amplifier linking

7

Wire connection

7

Fuses

7

General Installation Precautions

8

Before you install

8

Battery and charging system

8

Wire routing

8

Installation—AmplifierMounting

9

Choose the mounting location

9

Height, width, and depth diagrams

9

Installation—amplifiermounting (cont.)

10

Passenger & trunk compartment mounting

10

Installation—Fusesand Wiring

10

Amplifier fuses

10

Wire gauge

10

Installation—fusesand wiring (cont.)

11

Power/B+ and power/ground (GND) connection

11

Remote input connection

11

Speaker output connection

11

Installation—fusesand wiring (cont.)

12

Mono subwoofer operation

12

Setup Tuning—Full-RangeSpeakers

12

Music

12

Sensitivity controls

12

Highpass and lowpass crossover controls

12

Setup tuning—full-rangespeakers (cont.)

13

Head unit

13

Volume

13

Input sensitivity control

13

Crossover controls

13

Setup tuning—full-rangespeakers (cont.)

14

“Q” control

14

Setup Tuning—RearFill Speakers

14

Setup Tuning—Subwoofers

14

Input switch

14

Setup tuning—subwoofers(cont.)

15

Head unit

15

Volume

15

Input sensitivity control

15

Lowpass crossover control

15

Phase

15

System Examples

16,17

Amplifier Troubleshooting Guide

18

Contact and Warranty Information

19

2

Parts List

Included Hardware: GT-28&GT-24

(1) owner’s manual

(1) female quick-connectterminal for remote input

(1) 2mm hex wrench (for speaker input)

(1) 3mm hex wrench (for power input)

(6) mounting screws

Features and Specifications

GT-28andGT-24Features

2-Channel,High-CurrentAmplifier

2Ω 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-factorSettings

Selectable Highpass, Lowpass, and Bandpass Settings

Bandpass Configurable for Midbass or Subwoofer

Terminals Accept Bare, Heavy-GaugeWire

Screw-DownSecurity Cover Protects Tuning Controls

Optional Remote Subwoofer Level Control

Technical Specifications

 

 

 

GT-28

GT-24

14.4VDC Power

 

 

@ 4 Ohms

2x250W

2x175W

@ 2 Ohms

2x450W

2x275W

@ 4 Ohms (mono)

1x900W

1x550W

@ 2 Ohms (mono)

1x1350W

1x900W

 

 

 

12.6VDC Power

 

 

@ 4 Ohms

2x200W

2x120W

@ 2 Ohms

2x350W

2x200W

@ 4 Ohms (mono)

1x700W

1x440W

@ 2 Ohms (mono)

1x1100W

1x750W

 

 

 

Frequency Response (-3dB)

10Hz–95kHz

10Hz–95kHz

Signal-to-NoiseRatio (A Weighted)

>100dB

>100dB

Dimensions (HxWxD)

21/4x215/8x87/8” (57x548x225mm)

21/4x18x87/8” (57x458x225mm)

3

Control Functions

3

 

 

9

 

7

 

6

 

5

 

 

 

 

 

 

STEREO

MONO

OFF

ON

 

 

OFF

ON

OFF

ON

 

 

 

 

FUSE 4 x 25A

INPUT

L

SUBWOOFER LEVEL

LOWPASS SLOPE

 

LOWPASS

 

HIGHPASS

 

 

 

 

 

 

 

 

 

 

12dB

12dB 24dB

 

350

 

350

 

 

 

 

 

 

 

 

 

 

ST

MONO

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

200

Hz

185

Hz

 

 

 

 

 

 

 

 

 

 

 

 

 

50

 

20

 

MONO

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0.2

 

1.2

L

R

B+

B+

GND

GND

 

 

 

 

INPUT SENSITIVITY

2.6

 

0.95

Q/HP

 

 

 

 

 

 

I NPUT

REMOTE

SUBWOOFER LEVEL

 

 

 

5

 

0.7

SPEAKER OUTPUT

 

 

 

 

 

 

 

 

 

 

12.6–14.4VDC

GROUND

 

 

 

 

 

4

 

 

8

 

 

 

 

 

 

 

 

 

 

 

 

 

GT-28Top Panel Shown

1

 

 

 

 

 

 

 

STATUS

MONO

12.6–14.4VDC

GROUND

 

 

9

 

 

B+

B+

GND

GND

 

L

R

 

 

 

ON

10

 

 

 

 

 

SAFE

 

 

 

 

2

 

 

 

 

 

 

GT-28Front Panel Shown

1 RCA Inputs

1

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.

2

2 Remote Input

Use the supplied FEMALE quick-connectorto 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

STEREO MONO

INPUT L

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.

4 Input Sensitivity Control

Turn control clockwise to increase the amplifier sensitivity to incoming signals. Turn control counterclockwise to decrease the amplifier sensitivity.

5 Highpass Crossover Controls

To use 12dB/octave crossover, move HIGHPASS switch to right-handposition. Highpass crossover frequency is adjustable from 20Hz to 350Hz by rotary control. (Moving switch toleft-handposition will bypass crossover functions.)

0.2

INPUT SENSITIVITY 2.6

5

OFF ON

HIGHPASS

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-handposition will bypass crossover functions.)

7 Lowpass Slope

Select appropriate crossover slope of 12 or 24dB/octave by moving LOWPASS SLOPE switch.

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 0.7–1.2.

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 ampli-

fier is in thermal shutdown condition. RED only indicates a fault condition, “SAFE.”

OFF ON

LOWPASS

350

200

Hz

50

LOWPASS SLOPE

12dB 12dB 24dB ST MONO

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 inch1 inch

Control Cover Removal and Reinstallation

The cover panel is secured with two (2) captive coin-slottedscrews.Coin-slot-ted screws allow a coin edge to be used as a screwdriver to remove the panel.

Multi-PositionMounting 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 accept4-gauge.Tighten with supplied hex wrenches.

Fuses

Amplifier accepts standard AT-styleautomotive 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-levelsignals 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—AmplifierMounting

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.

GT-28

GT-24

13mm (1/2")

225mm (87/8")

GT-28 (GT-24depth dimensions are the same)

57mm (21/2")

57mm (21/2")

458mm (18")

548mm (215/8")

9

Installation—AmplifierMounting (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—Fusesand 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-gaugestripped wire at the DC power and ground input terminals, and4-gaugeis recommended. Wire runs should be kept to the minimum practical length.

10