Boston Acoustics Car Amplifier GT 4100 User Manual

4-Channel Amplier Owners Manual  
GT-475  
GT-4100  
 
Parts List  
Included Hardware:  
GT-475  
GT-4100  
Installation Manual  
Female Quick-Connect Terminal  
(for remote turn-on input)  
2mm Hex Wrench  
1
1
1
1
1
1
4
1
1
6
3mm Hex Wrench  
Mounting Screws  
Specifications  
Technical Specifications:  
GT-475  
GT-4100  
Rated Power (CEA-2006-A):  
@ 4-Ohm (Stereo):  
@ 2-Ohm (Stereo)  
75 Watts x 4  
120 Watts x 4  
250 Watts x 2  
100 Watts x 4  
150 Watts x 4  
450 Watts x 2  
@ 2-Ohm (Mono)  
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):  
@ 2-Ohm (Mono)  
65 Watts x 4  
200 Watts x 2  
85 Watts x 4  
330 Watts x 2  
Frequency Response (-3dB):  
Signal-to-Noise Ratio (A Weighted):  
THD+N:  
10Hz–95kHz  
>100dB  
0.03  
10Hz–95kHz  
>100dB  
0.03  
Highpass Crossover:  
Frequency Range:  
Slope (dB Per Octave):  
20Hz - 350Hz  
12dB  
20Hz - 350Hz  
12dB  
Lowpass Crossover (Rear Channel Only):  
Frequency Range:  
Slope (dB Per Octave):  
50Hz - 350Hz  
12dB  
50Hz - 350Hz  
12dB  
Signal Voltage Input Range:  
Fuse Amp Rating:  
200mv - 8v  
40 Amp  
200mv - 8v  
80 Amp  
Dimensions:  
Width:  
Height:  
3
1
14 ⁄4(375mm)  
22 ⁄4(566mm)  
3
3
2 ⁄8(61mm)  
2 ⁄8(61mm)  
Depth:  
9” (229mm)  
9” (229mm)  
3
 
Connections  
GT-4100  
1
2
3
2
4
5
6
7
8
GT-475  
1
2
3
2
4
5
6
7 8  
u Front RCA Input  
v Remote Turn-On (female spade connector supplied)  
w Rear RCA Input  
x Remote Gain Port (refer to GT-RSL manual for installation instruction)  
y Front Left/Right/Mono Speaker Outputs (12-gauge accepted)  
z Rear Left/Right/Mono Speaker Outputs (12-gauge accepted)  
{ 12v Power Input (4-gauge accepted)  
| Ground Wire Input (4-gauge accepted)  
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-4100  
10  
12  
11  
1
2
3
4
5
6
7
8
9
GT-475  
10  
12  
11  
1
2
3
4
5
6
7
8
9
u Signal Routing Switch (Sends Front RCA Signal to Rear Channels)  
v Front Channel Input Sensitivity (250mv to 8.0v - continuously variable)  
w Front Channel Highpass Frequency Adjustment (20Hz to 350Hz - variable)  
x Front Channel Highpass Crossover OFF/ON Switch  
y Front Channel Highpass Crossover Q-Tune Adj. (0.707 to 1.6 - variable)  
z 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  
Red  
Orange  
The Boston Logo will illuminate “Red” under normal operating conditions.  
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.  
5
 
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 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-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.  
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 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  
recommended. Wire runs should be kept to the minimum practical length.  
Power 12v and Ground (GND) Connection  
5
Strip approximately 8" (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  
5
Prepare each wire by stripping approximately 8" (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 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-OVER switches to the  
“OFF” position (refer to the diagram on page 5), with these settings, full-range signal is sent to the speaker  
outputs. Start with the front channels. If over-excursion is detected from speakers, move HIGHPASS switch to “ON”  
and slowly rotate clockwise until over-excursion is 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-Channel Highpass 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 maxi-  
mum undistorted playing level is heard from the speakers. Listen closely for bottoming from the speakers. If detect-  
ed, 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-Tune ” Control 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 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. 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 the Q-Tune that over-excursion may be detected in the  
front speakers; 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.  
Setting the Q-Tune is a subtle 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.  
fuse  
4-Channel Operation Wiring Configuration Diagram  
9
 
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  
 
Tuning The Amplifier - Front Speakers and Subwoofer (s)  
Highpass Crossover Control (Front Channel Only) Cont.  
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.  
6) Q-Tune™ Control (Front Channel 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 high-  
pass 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™ 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 a subtle 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.  
7) Rear Input Switch  
For dual RCA Input, set switch to STEREO. If one RCA is used, move switch to the right-hand (MONO) position  
(refer to the diagram on page 5)  
8) Lowpass Crossover Control (Rear Channels Only)  
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.  
9) RSL Control (Rear Channels Only)  
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.  
fuse  
3 Channel Operation Wiring Configuration Diagram  
11  
 
Amplifier Troubleshooting Guide  
Status LEDs 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 LEDs 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  
RCA cables are of good quality with no breakage to internal shields  
RCA cables from source to amplifier are not run alongside power  
Verify  
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 LEDs 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 a Shorted Speaker  
Verify  
Speaker crossover is not defective  
High-level cables from speaker to amplifier are not shorted  
Amplifier not Turning And Both LED (s) 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—Speakers, 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]  
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. 142-003179-1  
 

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