Radio Shack Trunk Mount User Manual

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Trunk Mount Amplifier

4-Channel 100-Watt

Cat. No. 12-1976

OWNER’S MANUAL

Please read before using this equipment.

4 × 25 Watt

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FEATURES

Your Optimus 4
Mount Amplifier is designed to pro­duce a total of 100 watts to give add­ed punch and power to your vehicle’s
existing stereo system.

The amplifier produces up to 25
watts per channel of clean, powerful
sound at all audio frequencies with
minimum distortion. And, you can
connect line-level as well as speaker
outputs to the amplifier.

Its features include:

14k Gold-Plated Noise-Isolated
Line-Level Input Jacks

connect low-level (pre-amplifier) sig­nal inputs to match your autosound
system’s output for the best high-fi­delity performance.

14k Gold-Plated Speaker Termi-

designed for low impedance,

nals

-

high conductivity, and m inimum cor­rosion to provide the highest signal
transfer and lowest sound distortion.

×

25 Watt Trunk

let you

-

Input Level Control

the level (high or low) of the audio
signals that enter the amplifier.

Automatic Power Switchin

matically turns on/off the amplifier
when you turn on/off your autosound
system.

Short Circuit Protection

sound if any output channel shorts to
protect the amplifier from damage.

Power Indi cator

is on.

If the connectors from your au-

Note:

tosound system are not compatible
with the amplifier’s connectors, your
local Radio Shack store sells adapter
harnesses for many vehicles.

lets you adjust

-

- auto -

distorts

-

lights when power

-

© 1995 Tandy Corporation.

Opti mus and Radio Shack are registered tr ademarks used by Tandy Corporation.

2

All Rights Reserved.

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CONTENTS

Preparation ..................................................................................................... 4

Choosing a Mounting Location .................................................................. 4

Before You Begin the Installation ............................................................... 4

Connecting Ground and Primary/Switched Pow er .................................... 5

Connecting Your Autosound System ......................................................... 7

Low Level Input Connections ............................ ....... ....... ..... ....... ....... . 7

High-level Input Connections ............................................................ 10

Connecting the Speakers ........................................................................ 13

Preparing the Speaker Wires ............................................................ 13

Connecting Four Speakers ................................................................ 14

Connecting Two Speakers ................................................................ 15

Testing the Connections .......................................................................... 16

Mounting the Amplifier ............................................................................. 16

Operation ...................................................................................................... 18

Turning On the Amplifier .......................................................................... 18

Setting the Level Control ......................................................................... 18

Maintenance .................................................................................................. 20

Replacing the Fuses ................................................................................ 21

Replacing the Tube-Type Fuse ......................................................... 21

Replacing the Blade-Type Fuse ........................................................ 21

Specifications ............................................................................................... 22

3

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PREPARATION

CHOOSING A MOUNTING LOCATION

The ideal location for mounting the amplifier is in your vehicle’s trunk. Wherever
you decide to mount it, choose a mounting location that:

• Does not interfere with the vehicle’s operation

• Lets you drill mounting holes without damaging other vehicle components

• Allows enough space around the cooling fins for proper airflow and cooling
The amplifier gets very hot while it is on. Do not touch the amplifier or

Warnin

place flammable objects near it while it is on.

BEFORE YOU BEGIN THE INSTAL LATION

Before you install your amplifier, carefully read all the instructions in this owner’s
manual. You should be able to answer all of these questions about your vehicle’s
electrical and sound systems.

:

• Does my vehicle have a 12-volt negative ground system? (If it does not, you

cannot use this amplifier.)

• Which of the amplifier’s wires is the power wire?

• How do I connect a wire to the fuse box?

• Which amplifier terminals are line-level inputs, which are speaker-level

inputs, and which are speaker outputs?

Important!

• Be aware that installation in your vehi cle may require cutting or modifying

your vehicle.

• Do not cut any of the amplifier’s wires. If you cut any wir e, you cannot obtain

a refund or exchange on this product. Rad io Shack wil l provide warranty
service if you cut a wire and find the product is defective.

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Cautions:

• To prevent damage to your amplifier or autosound system, you m ust first
connect the ground, primary, and switched power wires (as described in
“Connecting Ground and Primary/Switched Power” bef ore you connect the
speakers to the amplifier. Make the connections only in the order shown.
Damage to the amplifier is possible if you connect any wire incorrectly.

• Turn on the power to test the connections before you permanen tly mount
the amplifier (see “Testing the Power Connections”).

• Be sure y our speakers can handle 25 wa tts per channel i f you connect the
autosound system to two pairs of speakers (or 50 watts per channel if you
connect the autosound system to only one pair of speakers). Each speaker
must have an impedance of at least 4 ohms. Your local Radio Shack store
carries a full line of speakers to choose from.

CONNECTING GROUND AND PRIMARY/SWITCHED
POWER

1. To prevent damage to your amplifier or autosound system while m aking the
connections, disconnect the negative (

) cable from your vehicle’s battery.

-

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Note: After you complete th e connections and reconnect the battery wire,
you will need to reset all clock/tim er/memory devices in your vehicle.

2. Connect the supplied dark blue/white wire’s end to the amplifier’s
(remote power) terminal.

3. Securely connect the supplied dark blue/white wire’s male quick disconnect
plug to your autosound system’s switched power lead.

This connection turns your amplifier on or off when you turn your autosound
system on or off.

Note: If your autosound system does not have a remote power output lead,
connect this wire to a point in your vehicle’s ignition switch that provides 12­volt battery power when the ignition is set to ON or ACC. This connection
turns on the amplifier when you turn your i gnition switch to on (or to ACC)
and turns off the amplifier when you turn off the ignition.

4. Connect the black wire’s spade connector to the amplifier’s

5. Securely connect the black wire’s eyelet-terminal to a nearby metal ground,
such as a bolt attached to a part of the vehicle’s chassis.

Note: Be sure the bolt is n ot insulated from the chas sis by a p lastic part or
other insulating material.

6. Connect the red wire’s spade connector to the amplifier’s

7. Remove the nut from t he battery’s positive (
red wire’s 10A fused eyelet terminal over the end of the bolt.

Caution: Due to the amplifier’s high current requirement, you MUST con­nect the red wire’s fused end directly to the vehicle’s positive (
cable terminal or damage to your vehicle’s wiring could result.

) terminal bolt, the n pl ace t he

+

GND

+12V

terminal.

REM

termi n al.

) battery

+

Note: Do not reconnect your vehicle battery’s negative (

6

) cable yet.

-

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CONNECTING YOUR AUTOSOUND SYSTEM

Low Level Input Connections

You can connect your autosou nd system’s low-level phono output jacks to the
amplifier’s

Note:

and the amplifier, the amplifier’s
For the best results, use shielded audio cables, such as Cat. No. 42-2368 (not

supplied). If your autosound system has only two phono out puts, you will also
need two shielded Y-adapter cables, such as Cat. No. 42-2435 (not supplied).

1. Temporarily place the am plifier as close as possible to the s elected mount-

2.

LOW INPUT

phono jacks.

For a cleaner, less n oisy signa l t ransfe r between your autosound s ystem

LOW INPUT

phono jacks are gold-plated.

ing location.

If your autosound system has four phono output s and you are using four
speakers

as follows: front-left to
and rear-right to

, connect the autosound system to the amplifier using audio cables

FRONT L

REAR R

, front-right to

:

FRONT R

, rear-left to

REAR L

,

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If your autosound system has four phono outputs but you are using only two
speakers (front or rear)

, connect only the corresponding autosound sys-

tem’s output jacks to the amplifier using audio cables as follows:

• front-l e ft to

• rear-left to

FRONT L

REAR L

and front-right to

and rear-right to

FRONT R

REAR R

, or

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If your autosound system has only two phono output jacks (left and right)
and you are using f our speak ers,

a Y-adapter shielded audio cable to each autosound system output jack.
Then:

• Connect the oth er two ends o f the left Y-ada pter to the amplifier ’s corre­sponding

FRONT L

and

• Connect the other two ends of the right Y-adapter to the amplifier’s corre­sponding

FRONT R

and

REAR L

REAR R

first connect the singl e pho no pl ug end of

phono jacks

phono jacks

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If your autosound system has only two phono output jacks (left and right)
and you are using only two speakers,

corresponding

FRONT L

and

FRONT R

simply connect them to the amplifier’s
, or

REAR L

and

REAR R

phono jacks.

High-Level Input Connection s

If your st ereo system h as onl y speaker outp uts, yo u can connect th em to th e am­plifier’s re ar

HIGH INPUT

and front

connection or the common ground connection method.

10

HIGH INPUT

sockets using the floating ground

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If your autosound system has four speaker outputs and you are going to use four
speakers:

Floating
Ground
Connection

Common
Ground
Connection

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If your autosound system has only two speaker outputs and you are going to use
four speakers:

Floating
Ground
Connection

Common
Ground
Connection

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CONNECTING THE SPEAKERS

With the speakers plac ed in their approximate locations, run one speaker w ire
from each speaker to the amplifier. We recommend you use 16- or 18-gau ge
marked or color-coded wires to he lp you correct ly connec t th e speak ers t o your
amplifier. For the maximum bass respons e and the best overall performance,
keep your speakers properly phased (connect + to + and

to -).

-

Caution:

ground.

Note:

ning down one of the conductors or different colored insulation for each conduc­tor. Your local Radio Shack store has a wide selection of speaker wire to choose
from.

Do not connect the speakers’ negative (

Speaker wires have two conductors. Color-coded wires have a stripe run-

) terminal wires to chassis

-

Preparing the Speaker Wires

1. Separate each speak er wire’s two conductors at both ends for a length of
about 4 inches.

2. Strip the insulation from the e nds of each conductor to expose
wire.

1

/4 inch of

Note:

Be sure to twist the ends to secure loose strands.

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Connecting Four Speakers

1. Connect one end of a speaker wire’s marked conductor to the amplifier ’s

FL

(front-left positive) terminal.

+

2. Connect one end of the speaker wire’s unmarked conductor to the ampli-

FL

fier ’s

3. Repeat Steps 1 and 2 to connect a speaker wire to the amplifier’s
right) terminals.

(front-left negative) terminal.

-

FR

(front-

4. Repeat Steps 1

RR

and

5. Connect the other ends of the four speaker wires so
front-left speaker,
and

(rear-right) terminals.

RR

to the rear-right speaker.

3 to connect speaker wires to the amplifier’s RL (rear-left)

-

FR

to the front-right speaker, RL to the rear-left speaker,

FL

connects to the

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Connecting Two Speakers

If you are connecting only two speakers, you can connect them to the amplifier’s

FL

front (

1. Connect one end of a speaker wire’s marked conductor to the amplifier’s

2. Connect the end of the speaker wire’s unmarked conduc tor to the ampli-

3. Repeat Steps 1 and 2 to c onn ec t a sp eaker wire to t he am plifier’s

4. Connect the other ends of the speaker wires so

and FR) or rear (RL and RR) speaker terminals.

FL

(front-left positive) or RL + (rear-left positive) terminal.

+

FL

−

fier’s

FR

speaker and
speaker and

(front-left negative) or RL − (rear-left negative) terminal.

−

(front-right) or RR + or RR − (rear-right) terminals.

FL

FR

to the front-right speaker, or RL connects to the rear-left

RR

connects to the rear-right speaker.

connects to the front-left

FR

+

and

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TESTING THE CONNECTIONS

Before you permanently mount the amplifier, temporarily reconnect your vehicle
battery’s negative (
the connections.

The amplifier is properly connected to the autosound system and speakers if you
can verify that the amplifier an d t he a uto sound system turn on properly and the
speakers’ sound is clear and unmuffled.

) cable, turn your vehicle’s ignition to ON or ACC, then test

-

If you cannot quickly verify that all components operat e properly,

turn off your vehicle’s ignition

tive (

) cable and recheck your connections.

-

If you verify that all components operate properly, mark the connections to insure
easy identification of each wire, then follow the instructions under “Mounting the
Amplifier.”

. Then disconnect your veh icle battery ’s nega-

immediately

MOUNTING THE AMPLIFIER

Before you begin mounting the amplifier, make sure you have the following sup­plied hardware necessary for mounting.

• 4 sheet-metal screws

• 4 spring washers

• 4 flat washers

Then confirm that the amplifier fits your vehicle’s mounting area.

Caution:

1. Temporarily disconnect your vehicle battery’s negative (

Be careful to not drill into anything behind the mounting surface

) cable again.

-

2. To make mounting mo re convenient, temporarily disconnec t the amplifier’s
wiring (ground, primary power, remote power, your autosound system’s
input, and speakers).

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3. Using the mounting holes on the amplifier as a guide, mark the locations for
the mounting holes.

4. Drill

9

/64-inch holes in the marked locations, being careful not to damage

anything behind the mounting surface.

5. Attach the amplifier to the mounting surface using the supplied sheet-metal
screws and washers.

6. Reconnect the wiring.

7. Reconnect your vehicle battery’s negative (

) cable.

-

17

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OPERATION

TURNING ON THE AMPLIFIER

The amplifier automatically turns on whenever you turn on your autosound s ys­tem. POWER lights when the amplifier is operating.

SETTING THE LEVEL CONTROL

For the best performance, you can adjust the level of the audio signals that enter
the amplifier by following these steps.

Cautions:

• The sound distorts if any output channel short s. Turn off the amplifier and
try to locate the short.

• To prevent draining the vehicle’s battery, do not play the amplifier for too
long using the ignition switch’s ACC position after turning off the veh icle’s
ignition.

1. Using a flat blade screwdriver, turn both
terclockwise to

The right level control is for the front speakers; the left level control is

Note:

for the rear speakers.

18

MIN

.

LEVEL MIN/MAX

controls fully coun-

12-197 6.fm Page 19 Tuesday, July 13, 1999 10 :01 AM

2. Temporarily turn up the autosound system’s volume control to about one­third of its full range.

Caution: Never turn the level controls up any farther than you need to get
clear sound at two thirds volume maximum.

LEVEL

3. Turn either the left or right

control clockwise until you can hear the

sound at a comfortable level.

4. Turn up the volume on your autosound system until the sound begins to dis­tort. Then immediately turn down the volume to the point just below where
distortion began.

5. Adjust the level controls unt il the volume is at the maximum level you want
the autosound system to produce.

6. Adjust the autosound system’s volume control to a comfortable listening
level.

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MAINTENANCE

Your Optimus 4
design and craftsmanship. The following sugge stions will help you care for
your amplifier so you can enjoy it for years.

×

25 Watt Trunk Mount Amplifier is an exam ple of superior

Keep the amplifier dry. If it gets wet, wipe it dry immediately.
Liquids can contain minerals that corrode electronic circuits.

Use and store the amplifier only in normal temperat ure envi ­ronments. Temperature extremes can shorten the life of elec­tronic devices and distort or melt plastic parts.

Handle the amplifier gently and carefully. Dropping it can
damage circuit boa rds and cases a nd cause the am plifier to
work improperly.

Keep the amplifier away from dust and dirt, which can cause
premature wear of parts.

CLEANER

Modifying or tampering with the a mplifier’s internal components can ca use a
malfunction and invalidate your amplifier’s warranty. If your amplifier is not per­forming as it should, take it to your loc al Radio Shack store for assistance.

20

Wipe the amplifier with a damp cloth occasionally to keep it
looking new. Do not use harsh chemi cals, cleaning sol ve nts,
or strong detergents to clean the amplifier.

12-197 6.fm Page 21 Tuesday, July 13, 1999 10 :01 AM

REPLACING THE FUSES

If the amplifier shuts down, you might need to replace the power wire’s 10-amp
tube-type fuse (such as Cat. No. 270-1072, not supplied), the 10-amp blade-type
fuse (such as Cat. No. 270-1081, not supplied) on the back panel, or both fuses.

Cautions:

• Do not use fuses with ratings other than those specified here. Doing so
might damage your amplifier.

• After replacing a fuse, let the amplifier cool down before you turn it on
again.

Turn off your autosound system, then disconnect your vehicle battery’s negative
(

) terminal.

-

Replacing the Tube-Type Fuse

1. Grasp the two ends of the power
wire’s fuse holder and twist them
counterclockwise, then pull the
ends apart.

2. Insert a new 10-amp, tube-type fuse into the longer of the two fuse-holder ’s
ends, then grasp the fuse-holder ’s two ends, push them in and twist them
clockwise to secure them.

Replacing the Blade-Type Fuse

1. Grasp the fuse’s plastic end and
pull it out.

2. Grasp the new fuse’s plastic end and simply push it in.

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SPECIFICATIONS

Output Power @ 14.4 VDC 1 kHz 10% THD

Front.................................................................................................25W

Rear ..................................................................................................25W

Frequency Response........................................................20– 20, 000 Hz (±3 dB)

Input Impedance

Low Input....................................................................................... 10 kOhms

High Input......................................................................................100 Ohms

Input Sensit iv it y (for 10% THD Output Power)

Low Input. . .........................................................................................150 mV

High Input..............................................................................................2.5 V

Power Supply Voltage ............................ DC 14.4 V Negative Groun d (10.5–16V)

Maximum Current Draw.................................................................................10A

Matching Speaker Impedance ............................................... 4 Ohms or Greater

Fuse Requirement ........................................................................................10 A

1

Dimensions .......................................................... 2

.....................................................................................(53

/4 ¥ 71/4 ¥ 81/4 Inches (HWD)

200 ¥ 210 mm)

¥

2

¥

2

¥

Net Weight......... ........................ ............ ............ ........... ................3.7 lbs (1.7 kg)

Specifications are typ ical; in dividua l u nits m ight v ary. Spec ificat ions are s ub ject
to change and improvement without notice.

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NOTES

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RADIO SHACK LIMITED WARRANTY

This product is warranted against defects for 1 year from date of purchase from Radio
Shack co mpany-o wned stores an d authorize d Radio Shack franchisee s and dealers .
With in this per i od, we wil l repair it without charge for parts and labor. Simply bring your
Radio Shack sales sl ip as proof of purchase date to any Radio Shack store. War ranty
does not cover transportation costs. Nor does it cover a product subjected to misuse,
accidental damage, alterati on or improper installation.
EXCEPT AS PROVIDED HEREIN, RADIO SHACK MAKES NO EXPRESS WARRAN­TIES AND ANY IMPLIED WARRANTIES ARE LIMITED IN DURATION TO THE DURA­TION OF THE WRITTEN LIMITED WARRANTIES CONTAINED HEREIN. Some states
do not pe r m it li mitatio n or ex cl us ion of im p lie d war ran ti e s; therefo r e, the af oresaid limi­tation(s) or exclu s ion(s) may not apply to the purchaser.

This warranty gives you specifi c legal rights and you may also have othe r rights which vary fr om
state to state.

We Service What We Sell

9/94

RADIO SHACK

A Division of Tandy Corporation

Fort Worth, Texas 76102

7A5 Printed in T ai wan