Boston Acoustics GT-275 User manual

2-Channel Amplifier Owners Manual

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
and ease-of-use of the GT Amplifier should come as no surprise. If you're new to Boston,
welcome -we think you've made a great choice.
Table of Contents
Parts list
Specifications
Connections
Top panel removal/installation
Controls
Status LEDs
Installation -General
Before you install
Battery and charging system
Wire routing
Choose the mounting location
Passenger & trunk compartment mounting
Multi-Position Mounting Feet
Vents
Installation - Wiring
Amplifier fuses
Wire gauge
Power 12v and ground (GND) connection
Remote input connection
Speaker output connection
Mono subwoofer operation
Tuning The Amplifier - Front or Rear Speakers
Music
Input sensitivity control
Highpass and lowpass crossover controls
Head unit
Volume
2-channel highpass operation switch configuration diagram
Input sensitivity control
Crossover controls
"Q" control
2-channel operation wiring configuration diagram
Tuning The Amplifier - Subwoofers
Input switch
Head unit
Volume
Input 'sensitivity control
Bridged lowpass with Q-Tune™ swit.ch configuration diagram
Lowpass crossover control
Highpass crossover control
GT-RSL
Bridged operation wiring configuration diagram
Amplifier Troubleshooting Guide
Service Information
2
3
4
5
6
7
8
10
12

Parts List
Included Hardware: GT-275 GT-2125 GT-2200 GT-2300
Installation Manual
1 1 1 1
Female Quick-Connect Terminal 111 1
(for remote turn-on input)
2mm Hex Wrench 1 1 1 1
3mm Hex Wrench 1111
Mounting Screws 4 4 4 6
Specifications
Technical Specifications: GT-275 GT-2125 GT-2200 GT-2300
Rated Power (CEA-2006-A):
@ 4-0hm (Stereo): 75 Watts x 2
125 Watts x 2 200 Watts x 2 300 Watts x 2
@ 2-0hm (Stereo)
120 Watts x 2 200 Watts x 2 350 Watts x 2 500 Watts x 2
@ 4-0hm (Mono) 225 Watts x 1 400 Watts x 1 700 Watts
xl 1000 Watts x 1
@ 2-0hm (Mono) 300 Watts x1600 Watts x 1 900 Watts x 1 1400 Watts x 1
Rated Power (12v):
@ 4-0hm (Stereo): 55 Watts x 2 95 Watts x 2
160 Watts x2260 Watts x 2
@ 2-0hm (Mono) 230 Watts x1475 Watts x 1 750 Watts x11175 Watts x 1
Frequency Response (-3dB): 10Hz-95kHz 10Hz-95kHz 10Hz-95kHz 10Hz-95kHz
Signal-to-Noise Ratio (A Weighted): >100dB >100dB >100dB >100dB
THD+N: 0.03 0.03 0.03 0.03
HighPass Crossover:
Frequency Range: 20Hz -350Hz 20Hz -350Hz 20Hz -350Hz 20Hz -350Hz
Slope (dB Per Octave): 12dB 12dB 12dB 12dB
LowPass Crossover:
Frequency Range: 50Hz -350Hz 50Hz -350Hz 50Hz -350Hz 50Hz -350Hz
Slope (dB Per Octave): 12dB
or 24dB 12dB or 24db 12dB
or 24db 12dB or 24db
Signal Voltage Input Range:
200mv- 8v 200mv - 8v
200mv- 8v 200mv - 8v
Fuse Amp Rating: 30
Amp 40 Amp 70 Amp 100 Amp
Dimensions:
Width: 8 :JA" (223mm) 13 'A" (337mm)
18 %" (477mm)
22 ';.j" (566mm)
Height: 2%" (61mm) 2%" (61mm) 2%"
(61mm) 2%" (61mm)
Depth: 9" (229mm) 9" (229mm)
9" (229mm)
9" (229mm)
3

G G
GT-275
GT-2300
GT-2200
oStereo RCA Input
8Remote Turn-On (female spade connector supplied)
eRemote Gain Port (refer to GT-RSL manual for installation instruction)
o Left/Right/Mono Speaker Outputs (12-gauge accepted)
•12v Power Input (4-gauge accepted)
(i) Ground Wire Input (4-gauge accepted)
GT-2125
Connections
B!P 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

5
GT-275
~
~
~
,", . ..,...;-.-;
.---0
0000
Orange
Red
GT-2300
oStereo/Mono Switch
8Remote Gain OFF/ON Switch (ON when using GT-RSL)
C) Lowpass Slope Switch (12dB Stereo, 12dB Mono, or 24dB Mono)
oLowpass Crossover OFF/ON Switch (OFF/12dB/24dB on GT-275)
fit Lowpass Frequency Adjustment (50Hz to 350Hz -continuously variable)
oInput Sensitivity (250mv to 8.0v -continuously variable)
8Highpass Crossover OFF/ON Switch
(3 Highpass Crossover Q-Tune™ Adjustment (0.707 to 1.6 - continuously variable)
CD Highpass Frequency Adjustment (20Hz to 350Hz -continuously variable)
«i> Fuse (replace with same value mini ANL only, refer to specifications on page 3)
GT-2200
GT-2125
Controls
Status
LEOs
The Orange LED (not visible unless lit) will illuminate during start-up and under fault conditions. If this
is
illuminated after start-up, please refer to troubleshooting on page 12.
The Boston Logo will illuminate "Red" under normal operating conditions.

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-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 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 aseat, 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 GTI8> amplifiers have top panel controls. If the amplifier is mounted under aseat, 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 atrunk, 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-stick tape, or by wedging into position. Amplifier should be mounted using the movable mounting feet
and
the provided mounting screws.
Multi-Position Mounting Feet
The mounting feet are designed to slide in both directions to clear installation obstructions on the mounting
surface.
Vents (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 fai·lure.
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 con-
nected
to this wire, the fuse value should be of sufficient capacity to handle the demand.
Wire Gauge
The amplifier accepts up to 4-gauge stripped wire at the DC power and ground input terminals, and 4-gauge is
rp.commended.
Wire runs should be kept to the minimum practical length.
Power 12v and Ground (GND) Connection
Strip approximately %" (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-connect terminal 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-connect terminal 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 %" (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.
7

Tuning The Amplifier -Front Qr Rear Sp_ea_k_e_r_s _
1) Music
The material chosen for head unit/amplifier system setup 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) Input Sensitivity Control
Turn control 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 LOWPASS switches to the
"OFF" position (refer
to the diagram on page 5), with these settings, full-range signal is sent to the speaker
outputs. Ifover-excursion is detected
from speakers, move HIGHPASS switch to "ON" and slowly rotate clockwise
until over-excursion
is eliminated.
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. Ifthe 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! Adistorted signal from the head unit sent to the amplifier can cause loudspeaker failure at higher
listening levels.
©
o
2-Channel Highpass Operation Switch Configuration Diagram
8

9
-
-
-
-
+
--
--
2-Channel Operation Wiring Configuration Diagram
()
( J::
.. __ .. ::
Tuning The Amplifier - Front or Rear Sp_e_ak_e_'_s _
6) Input Sensitivity Control
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.
7) Crossover Controls
To achieve higher undistorted playing levels from the main 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.
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 counterclock-
wise 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.
8) Q-Tune'M Control
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 the Q-Tune'· that over-excursion may be detected in the
front speakers; lowering the
Q-Tune'M input sensitivity or raising the highpass crossover point will eliminate this.
Minor adjustments to each setting are required to fine-tune the system.
Setting the Q-Tune'· is asubtle process. It is recommended that the Q-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 the Q-Tune""
setting are all that are required to fine-tune the system.

Tuning The Amplifier -Subwoofer (5)
1) Input Switch
Move switch to the right-hand (MONO) position (refer to the diagram on page 5); the inputs are summed to
mono. Connect the
subwoofer to the speaker output terminals marked for mono operation. NOTE: Subwoofer
impedance is 2ohms minimum.
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! Adistorted signal from the head unit sent to the amplifier can cause speaker failure at higher
listening levels.
4) Input Sensitivity Control
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.
Bridged Lowpass with Q- Tune™ Switch Configuration Diagram
10

11
-
-
-
-
+
Bridged Operation Wiring Configuration Diagram
e ( ) ::)
••
.. __ ....
7) Q-Tune™ Control
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 highpass crossover point.
Tuning The Amplifier - Subwoofer (5)
5) Lowpass Crossover Control
Move the selector switch to "ON" (refer to the diagram on page 5). In this setting, lowpass signal is sent to the
speaker outputs.
Experiment with the crossover point settings while the subwoofer is active. A higher setting
will increase the perceived output, and a lower setting will make the bass response more omnidirectional. 12
or 24dB crossover slopes are available. Depending on your installation and listening preferences, one will
work more effectively.
6) Highpass Crossover Control
With some subwoofer applications, it may be necessary to use the highpass crossover to protect the subwoofer from
over-excursion.
Move the selector switch to "ON" (refer to the diagram on page 5) The highpass should be set
to the tuning frequency (vented) or the FS of the subwoofer (sealed or freeair) Ifyou are using aBoston
Acoustics® subwoofer, the correct highpass frequency and Q-Tune'· settings for that enclosure are outlined in the
subwoofer's owners manual.
Setting the Q-Tune'·
is asubtle process. It is recommended that the Q-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 the Q-Tune'·
setting are all that are required
to fine-tune the system.
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 the Q-Tune'· that over-excursion may be detected in the
subwoofer
(s); lowering the Q-Tune'· input sensitivity or raising the highpass crossover point will eliminate this.
Minor adjustments to each setting are required to fine-tune the system.
8) RSL Control
The remote level control (GT-RSL) gives you independent level adjustment of the subwoofer's output level beyond
the standard system volume control.
Please refer to the RSL's manual for installation instruction. The GT-RSL is
available separately, please consult your authorized Boston Acoustics dealer.

Amplifier Troubleshooting Guide
Status LEOs on Amplifier not Lit-Head Unit (Source) Turned "ON"
Verify Remote turn-on wire from source to amplifier has proper voltage
Power (B+) connections at amplifier, terminal blocks, and battery are secure
Ground (GND) connections at amplifier and vehicle chassis are secure
Battery
B+ fuse and amplifier fuse are OK
B+ at battery and B+ at amplifier have proper voltage
Status
LEOs Lit, no Output from Speakers-Speakers in Normal Operating Condition
Verify High-level cables from speaker(s) to amplifier are securely connected
RCA cables from amplifier to source are securely connected
Sensitivity adjustment on amplifier is correctly adjusted
Engine Noise
from Speaker(s)
Turn source "OFF" and disconnect
RCA cables at amplifier
If noise stops, check equipment and cables leading to amplifier
Verify
RCA cables are of good quality with no breakage to internal shields
RCA cables from source to amplifier are not run alongside power
Amplifier
Output Distorted-Music not Recorded with Intentional Distortion
Verify Source output to amplifier is not distorted
Amplifier input sensitivity is correctly adjusted
Amplifier Shutting Down, Red Blinking and Orange LEOs Lit-Amplifier in Thermal Protection Mode
Verify Amplifier is mounted with adequate air circulation around vents
Amplifier does not have obstructions blocking back or side panel vents
Amplifier is not mounted under carpet
Speakers meet correct impedance
for application (mono or stereo hookup)
Amplifier
not Turning "ON", Orange LED Lit-Amplifier not Connected to aShorted Speaker
Verify Speaker crossover is not defective
High-level cables from speaker to amplifier are not shorted
Amplifier
not Turning And Both LED (sl Blinking-Speakers, Crossovers, and Cable OK
Internal fuse needs to be replaced
Verify Replace fuse
with fuse of same value
Amplifier not Turning "ON", Orange LED Lit-5peakers, Crossovers, and Cable OK
Amplifier requires service
If Service Seems Necessary
First, contact the dealer from whom you purchased the product, or contact us via e-mail at:
USA and Canada: [email protected]
Europe: [email protected]
Japan: [email protected]
Asia/Pacific countries: [email protected]
We will promptly advise you of what action to take.
Boston Acoustics, Inc. 300 Jubilee Drive, Peabody,
MA 01960 USA
T: 978.538.5000 F: 978.538.5100 W: bostonacoustics.com
Boston, Boston GT, Boston Acoustics, and the Boston Acoustics logo are registered trademarks and DualMode and Q-Tune are trademarks of Boston Acoustics, Inc.
Specifications are subject to change without notice. ©2008 Boston Acoustics, Inc. All rights reserved. Covered by patents issued and/or pending. 142-003178-0