5-Channel, High-Current/High-Power Amplier

Table of Contents

Parts List Features and Specications Control Functions
Control functions (cont.) Control functions (cont.)

Mechanical Functions

Control cover removal and reinstallation Multi-position mounting feet Mechanical functions (cont.) Vents Amplier linking Wire connection Fuses
General Installation Precautions
Before you install Battery and charging system Wire routing
InstallationAmplier Mounting
Choose the mounting location Installationamplier mounting (cont.) Passenger and trunk compartment mounting
InstallationFuses and Wiring
Amplier fuses Wire gauge Installationfuses and wiring (cont.) Power/B+ and power/ground connection Remote input connection Speaker output connection Installationfuses and wiring (cont.) Mono subwoofer operation
Setup TuningFull-Range Speakers
Music Front, rear, and subwoofer sensitivity controls Front, rear, and subwoofer crossover controls Setup tuningfull-range speakers (cont.) Head unit Volume Front and rear input sensitivity control Front and rear crossover controls Setup tuningfull-range speakers (cont.) Front and rear Q-factor adjustments Rear input sensitivity and crossover controls

Setup TuningSubwoofers

Subwoofer level control Subwoofer mode switch Setup tuningsubwoofers (cont.) Head unit Volume Subwoofer sensitivity control Subwoofer crossover control Phase
System Examples Amplier Troubleshooting Guide Contact and Warranty Information

Parts List

Included Hardware
(1) owners 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 Specications

GT-50 Features

5-Channel, High-Current Amplier 2 Mono Operation Advanced Cooling Allows Varied Mounting Positions Adjustable Feet for Varied Mounting Surfaces Security Cover Protects Control Settings Power Increase with Input Voltage Rise Continuously Variable Crossovers and Q-factor Settings Selectable Highpass Front and Rear Channels Discrete Subwoofer Channel Inputs Selectable 24dB or 12dB Subwoofer Lowpass Setting Optional Remote Subwoofer Level Control Enhanced Switching Assignments

GT-50 Specications

14.4VDC Power Multi-Channel Power @ 4 Multi-Channel Power @ 2 Mixed Op. Power @ 4, 2 12.6VDC power Multi-Channel Power @ 4 Multi-Channel Power @ 2 Mixed Op. Power @ 4, 2 Frequency Response (-3dB) Signal-to-Noise Ratio (A Weighted) Dimensions 4x55W, 1x250W 4x85W, 1x350W 4x55W, 1x400W
4x45W, 1x190W 4x65W, 1x250W 4x45W, 1x300 10Hz95kHz >100dB 21/4x215/8x8 7/8 (57 x 548 x 225mm)

Control Functions

OFF H I G H PA S S ON STEREO

MONO L+R REAR INPUT OFF

ON H I G H PAS S STEREO
FRO NT + REAR M O NO L OFF
ON S U B WO O F E R L E V E L
N O N P R I N TA B L E A R E A
L OW PA S S O F F d B 24dB FUSE 3 x 30A

350 200

20 0.2
IN P U T S E N S ITIV I T Y

20 1.2 0.95

Q/HP INPUT SENSITIVITY

50 1.2 0.95

Q/HP INP UT SENSITIVITY L R L R B+ B+ G ND G ND

0.2 2.6

R E M OT E
RE M OTE SUBWO O FER LEVEL
FRO NT S P E AKE R O UTPUT

REAR SPEAKER OUTPUT

S U B WO O F E R O U T P U T

P OW E R

STATUS
F RO N T SPEA K ER O U T PU T
R EA R SPEA K ER O U T PU T
SU B WO O F ER O U T PU T B+

ON SAFE

1 FRONT RCA Inputs
RCA cables marked FRONT from head unit or from other line level device should be connected here. Use both inputs (L & R) for stereo.
2 FRONT, REAR, and SUBWOOFER Remote Inputs
Use the supplied FEMALE quick connector to connect the REMOTE trigger lead from the head unit to the amplier. Amplier turns ON when head unit is turned ON. One FEMALE.210" connector is supplied with amplier. The remote inputs are all in parallel. Only one is to be used. Use any one of the three remote inputs to turn the amplier on. Do not connect external 12-volt accessories to these inputs.
3 FRONT, REAR, and SUBWOOFER Input Sensitivity Controls
Turn control clockwise to increase the amplier sensitivity to incoming signals. Turn control counterclockwise to decrease the amplier sensitivity.
4 FRONT and REAR Highpass Crossover Controls
To use 12dB/octave crossover, move 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 HIGHPASS ON

Control Functions (cont.)
5 FRONT and REAR Q Controls
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.

+1.6dB 0dB -3dB

.707.95 1.2
t (tuned crossover frequency)

6 REAR RCA Inputs

RCA cables marked REAR from head unit or other line level device should be connected here. Use both inputs (L & R) for stereo.

7 REAR Input Switch

In the left (STEREO L-R) position, the L & R inputs go to the REAR L & R channels of the amplier. In the right (FRONT L-R) position, the inputs are derived from the FRONT channels and sent to the REAR L & R channels of the amplier.

STEREO REAR INPUT FRON T

8 SUBWOOFER RCA Inputs
RCA cables marked subwoofer from head unit or other line level device should be connected here. Use both inputs (L & R) for dual subwoofer output from head unit. Use left (L) input only when single subwoofer output is to be connected.
9 Lowpass Slope and Crossover Controls
Select appropriate crossover slope of 12 or 24dB/octave by moving LOWPASS SLOPE switch. Lowpass crossover frequencies are adjustable from 50Hz to 350Hz by rotary control.
O FF ON LOWPASS OFF 12dB 24dB SUBWOOFER LEVEL
10 SUBWOOFER Mode Switch Move switch to left position (MONO L-R) when used with L & R subwoofer RCA outputs. Move switch to middle position (L-MONO) when used with single subwoofer RCA outputs. Move switch to right position (NON-FADING MONO) when subwoofer signal is to be derived from front and rear channels.

MONO L M ONO

NON-FADI NG M ONO
11 Subwoofer Level Control and Port Switch should be set to OFF when control circuit is not installed, (see optional subwoofer level control owners manual).

cover panel

12 Status LED Indicators GREEN indicates the normal operating condition; the amplier is ON. GREEN and RED together are normal when the amplier is rst turned ON; RED will turn off after a few seconds. When both GREEN and RED remain on, the amplier is in thermal shutdown condition. RED only indicates a fault condition, SAFE.

Recessed RCA Inputs

The input jacks are recessed into the body of the amplier 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.

Mechanical Functions (cont.)

Vents (Side and Rear)

The cooling vents must be kept clear of obstructions once the amplier is installed. Failure to do this could lead to premature thermal shutdown or amplier failure.

upper side vent

lower side vent

Amplier Linking

The design of the side panels enables multiple ampliers to be used together without additional hardware.

Wire Connection

Amplier 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.
Amplier accepts standard AT-style automotive blade fuses.

FUSE 3 x 30A

WARNING! Before driving the amplier 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 amplier during installation.
Battery and Charging System
In order for the amplier to function correctly, the electrical system of the vehicle should be professionally checked for overall electrical capacity. When used, the amplier will increase the demand on the battery and alternator. Therefore both should be thoroughly evaluated before installing the amplier to ensure they are in normal operating condition and able to handle the increased demand the amplier will present to the vehicles 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 amplier when this occurs.) It is helpful to diagram the wire layout rst before any installation is attempted.
Choose the Mounting Location
Plan your installation so that the amplier is mounted where adequate ventilation is available. Never mount an amplier 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)
OFF HIGHPAS S ON STEREO REAR INPUT MONO L+R HIGHPASS OFF ON STEREO MONO L FRONT + REAR SUBWOOFER LEVEL OFF d B dB OFF ON LOW PAS S FUS E 3 x A

INP UT SENS ITIV ITY

Q/HP INPUT S E NS ITIV ITY L R L R B+ B+ G ND G ND

REMOTE

REMOTE SUBWOOFER LEVEL

FRONT SPEAKER OUTPUT

RE AR S P E AKE R O UTP UT

SUBWOOFER OUTPUT

SUBWOOFER OUTPUT B+

57mm (21/4)

548mm (215/8)
InstallationAmplier Mounting (cont.)
Passenger and Trunk Compartment Mounting
If the amplier 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 amplier. All Boston GT ampliers have top panel controls. If the amplier is mounted under a seat, position the amplier 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 amplier to solid surfaces only. Do not mount to plastic trim panels. Do not mount the amplier with Velcro, doublestick tape, or by wedging into position. Amplier should be mounted using the movable mounting feet and the provided mounting screws.

Amplier Fuses

Although the amplier has internal fuses, additional fusing should be provided at the battery on the positive (+) power wire going to the amplier. 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 amplier if only the amplier 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 amplier 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.
InstallationFuses and Wiring (cont.)
Power/B+ and Power/GND Connection
Strip approximately 5/8" (16mm) of insulation. The positive (+) power wire is installed into the amplier 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 slide connector to connect the REMOTE trigger lead from the head unit to the amplier. Crimp connector to wire from head unit that controls remote turn-on (refer to head unit owners manual). Once the slide 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 wire is installed into the amplier terminal marked SPEAKER OUTPUT / +. The negative () speaker wire is installed into the amplier terminal marked SPEAKER OUTPUT / -. Tighten the Speaker Output, +, and - terminals with the supplied 2mm hex wrench to secure the wire 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.
F RO N T SPEA K ER O UT P UT

Mono Subwoofer Operation

Connect either a 2-ohm or 4-ohm subwoofer to a single (+) and (-) terminal (see System A, page 16). When using two (2) subwoofers, each subwoofer should be a minimum 4-ohm [or higher] impedance, (see System B, page 17). WARNING! Subwoofer impedance must not fall below 2 ohms when in MONO mode.

SU B WO O FER O U TPU T

1) Music
The material chosen for head unit/amplier 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) FRONT, REAR, and SUBWOOFER Sensitivity Controls
Turn controls all the way counterclockwise (minimum position). In this position, the amplier will be less sensitive to the input signal from the head unit.
3) FRONT, REAR, and SUBWOOFER Crossover Controls
Crossovers should be turned off during this phase of set-up. Move the HIGHPASS and FILTER switches to the OFF positionwith these settings, full-range signal is sent to the FRONT & REAR speaker outputs.
L OW PA SS O F F 12d B 24d B

SU B WO OF ER L EVEL

FRONT and REAR crossover controls

SUBWOOFER crossover control
Setup TuningFull-Range Speakers (cont.)

4) Head Unit

The head unit should have all controls such as bass, treble, balance, and fader set to the at 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 GREEN status LED is lit on the amplier.

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 amplier can cause loudspeaker failure at higher listening levels!
6) FRONT and REAR Input Sensitivity Controls
Slowly rotate control clockwise until maximum undistorted playing level is heard from the speakers. Listen closely for bottoming from the speakers. If detected, rotate FRONT Input Sensitivity counterclockwise until it is eliminated.
7) FRONT and REAR Crossover Controls
To achieve higher undistorted playing levels from the front speakers, the FRONT crossover must be engaged. Rotate crossover control fully clockwise. The highpass crossover point is now set at 350Hz. Rotate FRONT Q Control fully counterclockwise. Move crossover switch to the right (ON) position. Slowly rotate FRONT input sensitivity control clockwise until maximum undistorted playing level is heard from the speakers. Listen closely for bottoming from the speakers. If detected, rotate FRONT input sensitivity control counterclockwise until it is eliminated. Slowly rotate FRONT 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 FRONT input sensitivity control counterclockwise until it is eliminated and/or rotate the FRONT highpass crossover control clockwise to raise the crossover point.

OFF H I G H PA S S ON

8) FRONT and REAR Q Controls
Once the FRONT highpass crossover point has been determined, use the FRONT Q control to increase the bass information centered around the crossover point. Setting the front Q control is done in conjunction with setting the levels on the input sensitivity and highpass crossover frequency controls. You may nd while setting the Q that bottoming may be detected in the front speakers; lowering the Q input sensitivity or raising the highpass crossover point will eliminate this. Minor adjustments to each setting are required to ne-tune the system. Setting the Q is a subtle process. It is recommended that the Q 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 setting are all that are required to ne-tune the system.

9) REAR Input Sensitivity and Crossover Controls
Setting levels for the rear channels proceeds the same as for the front except for the elimination of the Q control settings. Crossover selector switch must be set to HP and lter switch must be set to ON. If the loudspeaker being used is capable of full-range operation, lter should be set to OFF.
OFF ON L OWPASS O F F 12d B 24d B SU B WO OF ER L EVEL
1) SUBWOOFER LEVEL Control
Refer to subwoofer level control in owners manual. If the control is not used, SUBWOOFER LEVEL switch must be set to OFF.

2) SUBWOOFER Mode Switch

Move switch to left position (STEREO L-R) when used with L&R subwoofer RCA outputs. Move switch to middle position (MONO L) when used with single subwoofer RCA outputs. Move switch to right position when subwoofer signal is to be derived from front and rear channels.
Setup TuningSubwoofers (cont.)

3) Head Unit

The head unit should have all controls such as bass, treble, balance, and fader set to the at 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 GREEN status LED is lit on the amplier.

4) 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 amplier can cause loudspeaker failure at higher listening levels!
5) SUBWOOFER Sensitivity Control
Turn controls all the way counterclockwise (minimum position). In this position, the amplier 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 subwoofers. Listen closely for faults such as bottoming from the subwoofer. If fault is detected, rotate REAR input sensitivity control counterclockwise until fault is eliminated. At this point, the maximum undistorted subwoofer playing level has been dened.
6) SUBWOOFER Crossover Control
Move the selector switch to LP and the FILTER switch to ON. In this setting, lowpass signal is sent to the REAR speaker outputs. Select 12 or 24dB/octave.

7) PHASE

Subwoofer phase is relative to the front loudspeakers. Correct electrical phase does not always mean correct acoustic phase. Swap positive (+) and negative (-) connections at the speaker outputs where the subwoofer is connected to the amplier. It is benecial to listen to the subwoofer connected in both phase conditions. The subwoofer should be left in the condition in which the strongest bass response is noted.

12.5LF

ON S AF E SAFE
SYSTEM AFront, Rear, and Single 2 Subwoofer (2 load)

to ground

to ground fuse fuse to
+ battery terminal + battery terminal

System Examples

SYSTEM BFront, Rear, and Dual 4 Subwoofers (2 load) with Discrete Subwoofer Input

(from processor)

12.5LF 12.5LF
Amplier Troubleshooting Guide
Status LEDs on Amplier not LitHead Unit (Source) Turned ON
Verify Remote turn-on wire from source to amplier has proper voltage Power (B+) connections at amplier, terminal blocks, and battery are secure Ground (GND) connections at amplier and vehicle chassis are secure Battery B+ fuse is OK Amplier fuse is OK B+ at battery and B+ at amplier have proper voltage
Status LEDs Lit, no Output from SpeakersSpeakers in Normal Operating Condition
Verify High-level cables from speaker(s) to amplier are securely connected RCA cables from amplier to source are securely connected Sensitivity adjustment on amplier is correctly adjusted
Engine Noise from Speaker(s)
Turn source OFF Disconnect RCA cables at amplier If noise stops, check equipment & cables leading to amplier Verify RCA cables are of good quality with no breakage to internal shields RCA cables from source to amplier are not run alongside power
Amplier Output DistortedMusic not Recorded with Intentional Distortion
Verify Source output to amplier is not distorted Amplier input sensitivity is correctly adjusted
Amplier Shuts Down, Red and Green LEDs are LitAmplier is in Thermal Protection Mode
Verify Amplier is mounted with adequate air circulation around vents Amplier does not have obstructions blocking back or side panel vents Amplier is not mounted under carpet Speakers meet correct impedance for application (mono or stereo hookup)
Amplier Does Not Turn ON, and Red LED is LitAmplier not Connected to a Shorted Speaker
Verify Speaker crossover is not defective High-level cables from speaker to amplier are not shorted
Amplier Does Not Turn ON, and Red LED LitSpeakers, Crossovers, and Cable are OK

Amplier requires service

Contact and Warranty Information

Limited Warranty (US)

For one (1) year from the date of purchase, Boston Acoustics will repair for the original owner any defect in materials or workmanship that occurs in normal use, without charge for parts and laborwhen purchased from an authorized Boston Acoustics retailer. If an authorized Boston Acoustics retailer installs your amplier, the warranty will be extended one (1) additional year. Installation of the amplier must be noted on the original purchase receipt. The receipt must be presented at the time a warranty claim is made. Your responsibilities are to use the system according to the instructions supplied, to provide safe and secure transportation to an authorized Boston Acoustics service representative, and to present proof of purchase in the form of your sales slip when requesting service. Excluded from this warranty is damage that results from abuse, misuse, accidents, shipping, or repairs or modications by anyone other than an authorized Boston Acoustics service representative. This warranty is void if the serial number has been removed or defaced. This warranty gives you specic legal rights, and you may also have other rights that vary from state to state.

If Service Seems Necessary
First, contact the dealer from whom you purchased the amplier. If that is not possible, write to: Boston Acoustics, Inc. 300 Jubilee Drive Peabody, MA 01960 U.S.A., or your authorized Boston Acoustics distributor We will promptly advise you of what action to take. If it is necessary to return your unit to the factory, please ship it prepaid. After it has been repaired, we will return it freight prepaid in the U.S.A. and Canada.
Boston, Boston Acoustics, and the Boston logo are registered trademarks of Boston Acoustics, Inc. 2003 Boston Acoustics, Inc. All rights reserved. Specications subject to change without notice.

www.bostonacoustics.com

300 Jubilee Drive Peabody, MA 01960 U.S.A. (978) 538-5000

P/N 042-001655-1

142-003708-0

GT-RSL

Remote Subwoofer Level Controller for GT Amplifiers
Boston Acoustics, Inc. 300 Jubilee Drive, Peabody, MA 01960 USA T: 978.538.5000 F: 978.538.5100 W: bostonacoustics.com
Boston, Boston Acoustics, Boston GT, and the Boston Acoustics logo are registered trademarks of Boston Acoustics, Inc. Specifications are subject to change without notice. 2009 Boston Acoustics, Inc. All rights reserved. Covered by patents issued and/or pending.

PACKAGE CONTENTS

The GT-RSL is supplied with the following items: RSL Controller Unit (knob, 13ft cable, mounting bracket) Mounting Screws for Controller unit RSL Controller VCA Board RSL Port Cover and Pre Attached Mounting Screws
4. Install the GT-RSL cover plate over the socket and tighten screws.

YOU WILL NEED

#1 Phillips Head Screwdriver 3mm Allen Wrench (for removing the GT amplifier top cover)

OPERATION

Clockwise rotation will increase the subwoofer level. Counterclockwise rotation will decrease the subwoofer level. It may be necessary to reset the input sensitivity on the subwoofer amplifier according to user preference and or musical material. No other adjustments are required after the initial installation and setup. Note: The GT-RSL is compatible with the GT-5750, GT-4100, GT-2300, GT-2200, GT-475, GT-2125, GT-50, GT-42, GT-40, GT-28, and GT-24
5. Determine a location for the RSL control in the front of the vehicle. Screws are supplied for the GT-RSL bracket mounting.
6. The GT-RSL can be removed from bracket mount for flush installation by sliding knob off and removing attachment nut. Cut out diameter is 516" (7mm)
INSTALLATION INSTRUCTIONS
1. Completely power down the audio system in the vehicle and remove the negative cable from the vehicle's battery.
7. Route cable through the vehicle to the amplifiers location. Slide the connector into the GT-RSL receptacle on the GT amplifier.
2. Remove (2) screws securing amplifier GT-RSL cover plate marked GT-RSL.
8. On the amplifier, move the GT-RSL switch to the on position.
3. Align the GT-RSL Control PC Board into the port slots on the amplifier and gently press into the place until seated. The GT-RSL PC Board should fit into amplifier without force.
9. Reconnect power to the vehicle. It may be desirable to readjust the gain on the amplifier to allow for greater range of adjustment from the GT-RSL.