Boston Acoustics GTA 502 User Manual

GTA

High Performance Two and

Four Channel Ampliers

Connections and Controls

GTA-502

GTA-802

GTA-504

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Speaker Level Input

RCA Input (Left and Right)

Gain (250mv to 5.0v - continuously variable)

Crossover Frequency Adjustment (50Hz to 200Hz - continuously variable)

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Q-Tune Equalization Boost (+6dB @ 45Hz)

Crosssover Filter Switch (HP / Off / LP)

GTA-RSL Port (Remote Gain)

Speaker Output Block (Left / Right) or (LF / RF / LR / RR on GTA-504)

Status LED (Blue = Normal / Red = Fault Mode)

Fuse (Replace with same value only, refer to specifications on page 2)

Power Block (12v / Remote / Ground)

Status LED

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

The LED will illuminate “Red” during start-up and under fault conditions. If the

LED is still red after start-up, please refer to troubleshooting on page 12.

Speaker Level Input Cable

GTA amplifiers offer a dedicated speaker level input for ease installation into

factory systems when an RCA (low level) signal is not available. Wiring code for

the cable is industry standard;

White Solid = Left Positive

Gray Solid = Right Positive

White w/ Black Stripe = Left Negative

Gray w/ Black Stripe = Right Negative

Warning: Do not connect both Speaker Level and RCAs into the amplifier at the

same time as damage to the amplifier may occur.

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!

Passenger and Trunk Compartment Mounting

If the amplifier is mounted under a seat, be sure that there is adequate space

around the amplifier once installed, 1” (25mm) recommended minimum. Do not

allow seat padding or other obstructive material to press down on the amplifier.

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 screw

mounts in the endpanels and with the provided mounting screws.

Cooling

Position the amplifier so that there is adequate space around the amplifier once

installed, 1” (25mm) recommended minimum.

Installation - Wiring

Amplifier Fuses

Although the amplifier has an internal fuse (s), 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 8-gauge stripped wire at the DC power and ground

input terminals, and 8-gauge is recommended as a minimum. Wire runs should

be kept to the minimum practical length.

Power 12v and Ground (GND) Connection

Strip approximately 5/8” (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

Connect the REMOTE trigger lead from the head unit to the amplifier using the

3mm hex wrench to tighten the connector on the power block of the amplifier.

(refer to the diagram on page 3).

Speaker Output Connection

Prepare each wire by stripping approximately ⁄8” (16mm) of insulation. The pos-

itive (+) speaker wires are installed into the amplifier terminals marked “SPEAK-

ER OUTPUT” / “+” (refer to the diagram on page 3). The negative (–) speaker

wires are installed into the amplifier terminals marked “SPEAKER OUTPUT” / “-

”. Tighten the “SPEAKER OUTPUT”, “+”, and “-” terminals with the supplied

3mm hex wrench (2mm on GTA-504) 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.

Note: Speaker outputs are marked “Front Output” and “Rear Output” on the

GTA-504.

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 3).

WARNING! Subwoofer impedance must not fall below 4 ohms when in

MONO mode.

Tuning The Amplifier - Front or Rear Speakers

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 (Gain)

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 3).

3) Crossover Control

Crossovers should be turned “OFF” during this phase of setup . Move the X-OVER

switch to the “OFF” position (refer to the diagram on page 3), with these settings,

full-range signal is sent to the speaker outputs. If over-excursion is detected from

speakers, move the switch to “HP” 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.

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 BLUE

status LED 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.)

Configuration and Co

GTA 2-Channel Amplifier Powering a Pair

Tuning The Amplifier - Front or Rear Speakers

WARNING! A distorted signal from the head unit sent to the amplifier can cause

loudspeaker failure at higher listening levels.

6) Input Sensitivity Control (Gain)

Slowly rotate the control clockwise (refer to the diagram on page 3) 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 3). The highpass crossover point is now set at 200Hz. Q-Tune

should be set to off.

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.

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8) Q-Tune Control

Q-Tune allows for +6dB boost of bass information centered at 45Hz and is not

typically needed for full range speaker applications.

fuse

onnection Diagram:

r of Full Range Speakers (80Hz Highpass)

Tuning The Amplifier - Subwoofer(s)

1) 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 Blue status LED (logo) is illuminated on the amplifier.

2) 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.

3) Input Sensitivity Control (Gain)

Turn control (refer to the diagram on page 3) 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.

Configuration and C

GTA 2-Channel Amplifier Poweri

Tuning The Amplifier - Subwoofer(s)

4) Crossover Control

Move the selector switch to “LP” (refer to the diagram on page 3). 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.

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5) Q-Tune Control

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Once the crossover point has been determined, you may choose to use Q-Tune to

increase the bass information. Q-Tune will offer a +6dB bass boost centered at 45Hz

which can be beneficial if more low bass output is desired. To engage Q-Tune move

the selector switch to the “ON” position (refer to the diagram on page 3).

6) GTA-RSL Control

The remote level control (GTA-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 GTA-RSL is available separately,

please consult your authorized Boston Acoustics dealer.