Radio Shack 85 User Manual

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Cat. No. 12-1977

OWNER’S MANUAL

Please read before using this equipment.

85 × 4 High Power 4-Channel

Trunk Mount Amplifier

ging

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FEATURES

Your Optimus 85 × 4 High P ower 4Channel Trunk Mount Amplifier is designed to produce a total of 340 watts to give added punch and power to your vehicle’s existing stereo system.

The amplifier produces up to 85 watts per channel of clean, powerful sound at all audio frequencies with minimum distortion. You can adjust the crossover frequency for both channels 3 and 4 when using only two speakers and a subwoofer, so you can emphasize the bass sou nds but not lose the other sounds or power. You can connect your autosound system’s line-level or speaker level 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.

let you

Input Level Controls

the level 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.

Brid

bine the amplifier’s four 85-watt channels so you can use the system with only two channels that produce a total of 170 watts from e ach channel.

Crossover Frequenc

you adjust the crossover frequency from 45 three and four when you use only two speakers.

Crossover Frequenc Switch

drive a connected subwoofer.

Automatic Thermal Protection S

ers the amplifier’s output power when the am plifier’s internal te mperature reaches 202×F the n i n cre a ses the output po wer when the amplifier cools down.

Capabilit

400 Hz for both channels

lets you set the amplifier to

stem (ATPS)

let you adjust

- auto -

- lets you com-

Circuit

ON/OFF

automatically low-

lets

Optimus and Radio Shack are registered trademarks used by Tandy Corporation.

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Mute Turn On Circuit - eliminates the irritating thump n oise that some amplifiers produce when you turn them on.

Power Indi cator is on.

Full MOSFET Power Supply duces enough power to supply the main amplifier and has a considerable amount of reserve power for peak “high demand” situations.

Short Circuit Protection sound if any output channel shorts so you can know to turn off the amplifier.

lights when power

pro-

distorts

Important: Be sure your speakers can handle 340 watts of power (1 70 watts per channel if you connect the autosound system to one pair of speakers, or 85 watts per channel if you connect the autosound system to two pairs of speakers). Each speaker must have a n im peda nc e of at least 4 ohms. Your local Radio Shack store carries a full line of speakers.

Note: If the connectors on your vehicle stereo system are not compatible with the amplifier’s connectors, your local Radio Shack store sells adapter harnesses for many vehicles.

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CONTENTS

Preparation ...... ...................... ........... ............ ..................... ............ ............ ..... 5

Choosing a Mounting Location .................................................................. 5

Before You Begin the Installation .............................................................. 5

Connecting Ground and Primary/Switched Power .................................... 6

Connecting to Your Autosound System ..................................................... 8

Low Level Input Connections .............................................................. 8

High-level Input Connections ............................................................. 11

Connecting the Speakers ........................................................................ 14

Preparing the Speaker Wires ............................................................ 14

Connecting Four Speakers ............................................................... 15

Connecting Two Speakers (Unbridged Connection) ......................... 16

Connecting Two Speakers (Bridged Connection) ............................. 17

Connecting Two Unbridged Speakers

and One Unbridged Subwoofer .................................................. 18

Connecting Two Unbridged Speakers

and One Bridged Subwoofer ...................................................... 19

Testing the Connections .......................................................................... 20

Mounting the Amplifier ............................................................................. 21

Operation ...................................................................................................... 23

Turning On the Amplifier .......................................................................... 23

Setting the Level Control ......................................................................... 23

Using the Frequency Crossover .............................................................. 24

X-Over Freq On/off Switch ................................................................ 24

X-Over Freq Control .......................................................................... 24

Maintenance ................................................................................................. 25

Replacing the Fuses ................................................................................ 26

Replacing the Tube-Type Fuse . ........................................................ 26

Replacing a Blade-Type Fuse ........................................................... 26

Specifications ............................................................................................... 27

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PREPARATION

CHOOSING A MOUNTING LOCATION

The ideal location for mounting the amplifier is in your vehicle’s trunk. Wherev er 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 componen ts.

• 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 INSTALLATION

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 inst allation in your vehicle may require cutting or modifying

your vehicle.

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

a refund or exchange on this product. Radio Shack will 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 must first connect the ground, primary, and switched power wires (as described in “Connecting Ground and Primary/Swi tched Po wer”) before you connect the speakers to the am plifier. 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 connect ions before you permanently mount the amplifier (see “T esting the Power Connections”).

• Be sure your speakers can handle 85 watts per channel , if you connect the autosound system to two pairs of speakers (or 170 watts per channel if you connect the autosound sy stem t o onl y one pair of speakers). Each speaker must have an i mpedance of at lea st 4 oh ms. 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 mak ing the connections, disconnect the negative (–) cable from your vehicle’s battery.

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.

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2. Securely connect the supplied dark blue/white wire’s spade connector end to the amplifier’s terminal.

3. Connect the dark blue/white wire’s

REM

(remote power)

(illus - pl ease add a dwg that illustrates step 3)

other end to your autosound system’s switched power lead using a twist-on terminal connector (such as Cat. No. 64-3057, not supplied).

If your autosound system does not have a remote power output lead,

Note:

connect this wire t o a poi nt in your vehicle’s fuse b ox that provi des 12 -volt battery power when the ignition is set t o ON or ACC. This connect ion turns on the amplifier when you turn your ignition switch to on (or to ACC) and turns off the amplifier when you turn off the ignition.

4. Connect the black wire’s eyelet/spade terminal end to the amp lifier’s tw o

GND

terminals.

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.

Be sure the bolt is not insulated from the chassis by a plastic part or

Note:

other insulating material.

6. Connect the red wire’s eyelet/spade terminal end to the amplifier’s two

+12V

terminals.

7. Remove the nut from the positive (

) cable’s terminal bolt, mount the red wire’s 50A fused eyelet terminal on the bolt, then replace and tighten the bolt.

Caution:

Due to the amplifier’s high

(illus - please add a dwg that illustrates step 7)

current requirement, you MUST connect the red wire’s fused end directly to the vehicle’s positive (

) battery

cable terminal b olt or damage t o your vehicle’s wiring could result.

Do not reconnect your vehicle battery’s negative (–) cable yet.

Note:

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CONNECTING TO YOUR AUTOSOUND SYSTEM

Low Level Input Connections

You can connect yo ur autosound system ’s low-level phono ou tput jacks to the amplifier’s low-level phono input jacks. For the best results, use shi elded audio cables, such as Cat. No. 42-2368 (not supplied).

Note:

For a cleaner, less noisy signal transfer be twee n your auto sound system

and the amplifier, the amplifier’s

1. Temporarily place the amplifier as close as possible to the selecte d mounting location.

If your autosound system has four phono ou tputs and you are using four

speakers

, connect the autosound system to the amplifier using audio cables

as follows: front-left to

CH4.

low input phono jacks are gold-plated.

CH1

, front-right to

CH2

, rear-left to

CH3

, and rear-right

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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 autosound system’s correspond-

ing output jacks to the amplifier using audio cables as follows:

• front-left to

• rear-left to

CH1

and front-right to

CH3

and rear-right to

CH2

CH4

, or

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