Boston Acoustics GT-4100 User Manual

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Table Of Contents

Introduction

Thank you for choosing Boston Acoustics® and congratulations on your purchase of the Boston GT® Amplifier. If you own other Boston products, the outstanding audio performance andease-of-useof the GT Amplifier should come as no surprise. If you’re new to Boston, welcome – you’ve made a great choice.

Table of Contents

Parts list

3

Specifications

 

Connections

4

Top panel removal / installation

 

Controls

5

Status LEDs

 

Installation - General

6

Before you install

 

Battery and charging system

 

Wire routing

 

Mounting location

 

Passenger & trunk compartment mounting

 

Multi-PositionMounting Feet

 

Venting

 

Installation - Wiring

7

Amplifier fuses

 

Wire gauge

 

Power 12v and ground (GND) connection

 

Remote input connection

 

Speaker output connection

 

Mono subwoofer operation

 

Tuning The Amplifier - Front and Rear Speakers

8

Music

 

Front signal routing switch

 

Input sensitivity control

 

Highpass and lowpass crossover controls

 

Head unit

 

Volume

 

4-channelhighpass operation switch configuration diagram

 

Input sensitivity control

 

Crossover controls

 

Q-Tune control

 

4-channeloperation wiring configuration diagram

 

Tuning The Amplifier - Front Speakers and Subwoofers

10

Front signal routing switch

 

Head unit

 

Volume

 

Input sensitivity control

 

Highpass crossover control

 

Q-Tune control

 

Rear input switch

 

Lowpass crossover control

 

GT-RSL

 

Bridged operation wiring configuration diagram

 

Amplifier Troubleshooting Guide

12

Service Information

 

2

Parts List

Included Hardware:

GT-475

GT-4100

Installation Manual

1

1

Female Quick-ConnectTerminal

1

1

(for remote turn-oninput)

 

 

2mm Hex Wrench

1

1

3mm Hex Wrench

1

1

Mounting Screws

4

6

 

 

 

Specifications

Technical Specifications:

GT-475

GT-4100

Rated Power (CEA-2006-A):

 

 

@ 4-Ohm(Stereo):

75 Watts x 4

100 Watts x 4

@ 2-Ohm(Stereo)

120 Watts x 4

150 Watts x 4

@ 2-Ohm(Mono)

250 Watts x 2

450 Watts x 2

Mixed Operation (CEA-2006-A):

 

 

@ 4-Ohm(Stereo) &2-ohm(Mono):

75 W x 2, 250 W x 1

100 W x 2, 450 W x 1

Rated Power (12v):

 

 

@ 4-Ohm(Stereo):

65 Watts x 4

85 Watts x 4

@ 2-Ohm(Mono)

200 Watts x 2

330 Watts x 2

Frequency Response (-3dB):

10Hz–95kHz

10Hz–95kHz

Signal-to-NoiseRatio (A Weighted):

>100dB

>100dB

THD+N:

0.03

0.03

Highpass Crossover:

 

 

Frequency Range:

20Hz - 350Hz

20Hz - 350Hz

Slope (dB Per Octave):

12dB

12dB

Lowpass Crossover (Rear Channel Only):

 

 

Frequency Range:

50Hz - 350Hz

50Hz - 350Hz

Slope (dB Per Octave):

12dB

12dB

Signal Voltage Input Range:

200mv - 8v

200mv - 8v

Fuse Amp Rating:

40 Amp

80 Amp

Dimensions:

 

 

Width:

14 34(375mm)

22 14(566mm)

Height:

2 38(61mm)

2 38(61mm)

Depth:

9” (229mm)

9” (229mm)

 

 

 

Specifications And Parts

3

Connections

Connections

G -40

1

2

3

2

4

5

6

7

8

G 4 5

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

 

 

2

 

 

 

 

3

 

2

 

 

4

 

 

 

 

 

5

 

 

 

 

 

 

 

 

 

 

 

 

 

6

 

 

 

 

 

 

 

 

7

 

 

8

 

 

 

 

 

 

 

υ Front RCA Input

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ϖ

Remote Turn-On(female spade connector supplied)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ω

Rear RCA Input

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ξ

Remote Gain Port (refer to GT-RSLmanual for installation instruction)

ψ

Front Left/Right/Mono Speaker Outputs (12-gaugeaccepted)

 

 

 

 

 

 

 

 

 

 

ζ

Rear Left/Right/Mono Speaker Outputs (12-gaugeaccepted)

 

 

 

 

 

 

 

 

 

 

{

12v Power Input (4-gaugeaccepted)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

|

Ground Wire Input (4-gaugeaccepted)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Top Panel Removal / Installation

The cover panel is secured with two (2) 3mm screws. Once unscrewed, pull panel forward, once clear of the corners of the end panels, it will lift off. Reverse to reinstall.

4

Controls

GT 1 0

1

2

3

4

5

6

7

8

9

1

11

12

GT 47

 

1

2

3

4

5

6

7

8

9

10 11

12

υ Signal Routing Switch (Sends Front RCA Signal to Rear Channels)

ϖ

Front Channel Input Sensitivity (250mv to 8.0v - continuously variable)

ω

Front Channel Highpass Frequency Adjustment (20Hz to 350Hz - variable)

ξ

Front Channel Highpass Crossover OFF/ON Switch

 

ψ

Front Channel Highpass Crossover Q-Tune Adj. (0.707 to 1.6 - variable)

ζ

Rear Channel Stereo / Mono Switch

 

 

 

 

{

Rear Channel Remote Gain OFF / ON Switch (ON when using GT-RSL)

|

Rear Channel Channel Highpass / Lowpass Crossover Selection Switch

}

Rear Channel Input Sensitivity (250mv to 8.0v - continuously variable)

 

Rear Channel HP / LP Frequency Adjustment (20Hz to 350Hz - variable)

Rear Channel Crossover OFF/ON Switch

Fuse (replace with same value mini ANL only, refer to specifications on page 3)

Status LEDs

Re

Or e

The Boston Logo will illuminate “Red” under normal operating conditions.

The Orange LED (not visible unless lit) will illuminate during start-upand under fault conditions. If this is illuminated afterstart-up,please refer to troubleshooting on page 12.

Controls

5

Installation - General

Installation - General

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 initiated.

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 lies behind that surface. Check for gas tank, brake lines, and any vehicle wiring harness.

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, double-sticktape, or by wedging into position. Amplifier should be mounted using the movable mounting feet and the provided mounting screws.

Multi-PositionMounting Feet

The mounting feet are designed to slide in both directions to clear installation obstructions on the mounting surface.

Venting (Side and Rear)

The cooling vents must be kept clear of obstructions once the amplifier is installed. If the vents are obstructed, this could lead to premature thermal shutdown or amplifier failure.

6

Installation - Wiring

Amplifier Fuses

Although the amplifier has an internal fuse, additional fuse protection should be installed as close as possible to 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 fuse of the amplifier if only the single 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.

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.

Power 12v and Ground (GND) Connection

Strip approximately 58" (16mm) of insulation. The positive (+) power wire is installed into the amplifier terminal marked “12v”. 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 12v 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 the insulation from fraying. 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.

Remote Input Connection

Use the supplied FEMALE quick-connectterminal to connect the REMOTE trigger lead from the head unit to the amplifier. Crimp connector to wire from head unit that controls remoteturn-on(refer to head unit owner’s manual). Once thequick-connectterminal is crimped into place, carefully push connector onto recessed MALE REMOTE terminal adjacent to the RCA input pair (refer to the diagram on page 4).

Speaker Output Connection

Prepare each wire by stripping approximately 58" (16mm) of insulation. The positive (+) speaker wires are installed into the amplifier terminals marked “SPEAKER OUTPUT” / “+” (refer to the diagram on page 4). 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 Subwoofer Operation

When the amplifier is configured for mono operation, use the speaker output terminals marked for mono use (refer to the diagram on page 4).

WARNING! Subwoofer impedance must not fall below 2 ohms when in MONO mode.

Wiring - Installation

7

Tuning - Front and Rear Speakers

Tuning The Amplifier - Front and Rear Speakers

1) Music

The material chosen for system tuning must be both clear in recording quality and dynamic in amplitude. Many audiophile “test” discs have musical tracks with both of these characteristics and should be used.

2) Front Signal Routing Switch

If using two sets of RCAs (independent front and rear RCAs), set the switch to DEDICATED FRONT AND REAR INPUTS . If you are using one set of RCAs for both front and rear channels, set the switch to SEND FRONT RCA SIGNAL TO REAR. (refer to the diagram on page 5).

2) Input Sensitivity Control

Turn both front and rear controls all the way counterclockwise (minimum position). In this position, the amplifier will be less sensitive to the input signal from the head unit (refer to the diagram on page 5).

3) Highpass & Lowpass Crossover Controls

Crossovers should be turned “OFF” during this phase of setup . Move the HIGHPASS and X-OVERswitches to the “OFF” position (refer to the diagram on page 5), with these settings,full-rangesignal is sent to the speaker outputs. Start with the front channels. Ifover-excursionis detected from speakers, move HIGHPASS switch to “ON” and slowly rotate clockwise untilover-excursionis eliminated. Repeat for the rear channels.

4) Head Unit

The head unit should have all controls such as bass, treble, balance, and fader set to the flat or centered position. The volume control should be at the minimum setting. If the head unit has any equalization or bass management features such as boost, they should be defeated at this time. Turn head unit on, and verify that the RED status LED (logo) is illuminated on the amplifier.

5) Volume

With the chosen musical track playing, turn the head unit volume control up until the maximum level of undistorted signal is heard from the speakers. (For most head units, this will be near the end of the volume control range.)

WARNING! A distorted signal from the head unit sent to the amplifier can cause loudspeaker failure at higher listening levels.

4-ChannelHighpass Operation Switch Configuration Diagram

8

Tuning The Amplifier - Front and Rear Speakers

6) Input Sensitivity Control

Starting with the front channels, slowly rotate the control clockwise (refer to the diagram on page 5) until maximum undistorted playing level is heard from the speakers. Listen closely for bottoming from the speakers. If detected, rotate the input sensitivity control counterclockwise until it is eliminated. Repeat for the rear channels.

7) Crossover Controls

To achieve higher undistorted playing levels from the both the front and rear speakers, the highpass crossover must be engaged. Starting with the front channels, rotate the crossover control fully clockwise (refer to the diagram on page 5). The highpass crossover point is now set at 350Hz. Rotate “Q-TuneControl fully counterclockwise (front channels only). Move crossover switch to the right (ON) position.

Slowly rotate the input sensitivity control clockwise until maximum undistorted playing level is heard from the speakers. Listen closely for bottoming from the speakers. If detected, rotate the input sensitivity control counterclockwise until it is eliminated. Slowly rotate the highpass crossover control counterclockwise while listening for bottoming. You are lowering the crossover point, which means that more bass signal is being sent to the speakers. If bottoming is detected, rotate the input sensitivity control counterclockwise until it is eliminated and/or rotate the Highpass crossover control clockwise to raise the crossover point. Repeat for the rear channels.

8) Q-Tune Control (Front Channels Only)

Once the highpass crossover point has been determined, use the Q-Tune control (refer to the diagram on page 5) to increase the bass information centered around the crossover point.

Setting the Q-Tune control is done in conjunction with setting the levels on the input sensitivity and highpass crossover frequency controls. You may find while setting theQ-Tune thatover-excursionmay be detected in the front speakers; lowering theQ-Tune input sensitivity or raising the highpass crossover point will eliminate this. Minor adjustments to each setting are required tofine-tunethe system.

Setting the Q-Tune is a subtle process. It is recommended that theQ-Tune setting be left in the 0.7 position and adjusted only after the input sensitivity and highpass crossover ranges are known. Small adjustments to theQ-Tune setting are all that are required tofine-tunethe system.

f

s

4-ChannelOperation Wiring Configuration Diagram

Speakers Rear and Front - Tuning

9

Tuning - Subwoofers

Tuning The Amplifier - Front Speakers and Subwoofer (s)

1) Front Signal Routing Switch

If using two sets of RCAs (independent front and rear RCAs), set the switch to DEDICATED FRONT AND REAR INPUTS . If you are using one set of RCAs for both front and rear channels, set the switch to SEND FRONT RCA SIGNAL TO REAR. (refer to the diagram on page 5).

2) Head Unit

The head unit should have all controls such as bass, treble, balance, and fader set to the flat or centered position. The volume control should be at the minimum setting. If the head unit has any equalization or bass management features such as boost, they should be deactivated at this time. Turn head unit on, and verify that the RED status LED (logo) is illuminated on the amplifier.

3) Volume

With the chosen musical track playing, turn the head unit volume control up until the maximum level of undistorted signal is heard from the speakers. For most head units, this will be at the end of the volume control range.

WARNING! A distorted signal from the head unit sent to the amplifier can cause speaker failure at higher listening levels.

4) Input Sensitivity Control (Front and Rear Channels)

Turn control (refer to the diagram on page 5) all the way counterclockwise (minimum position). In this position, the amplifier will be less sensitive to the input signal from the head unit. Slowly rotate this control clockwise until maximum undistorted playing level is heard from the subwoofer(s). Listen closely for faults such as bottoming from the subwoofer(s). If fault is detected, rotate input sensitivity control counterclockwise until fault is eliminated. At this point, the maximum undistorted subwoofer playing level has been defined.

5) Highpass Crossover Control (Front Channel Only)

To achieve higher undistorted playing levels from the front speakers, the highpass crossover must be engaged. Rotate the crossover control fully clockwise (refer to the diagram on page 5). The highpass crossover point is now set at 350Hz. Rotate “Q-Tune™”Control fully counterclockwise. Move crossover switch to the right (ON) position.

Bridged Lowpass with Q-Tune Switch Configuration Diagram

10