Radio Shack Stereo Amplifier Trunk Mount User Guide

12-1976.fm Page 1 Tuesday, July 13, 1999 10:01 AM  
Cat. No. 12-1976  
OWNER’S MANUAL  
Please read before using this equipment.  
×
4 25 Watt  
Trunk Mount Amplifier  
4-Channel 100-Watt  
 
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CONTENTS  
Preparation ..................................................................................................... 4  
Choosing a Mounting Location .................................................................. 4  
Before You Begin the Installation ............................................................... 4  
Connecting Ground and Primary/Switched Power .................................... 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  
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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  
Warning: The amplifier gets very hot while it is on. Do not touch the amplifier or  
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 installation 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/Switched Power” before 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 permanently mount  
the amplifier (see “Testing the Power Connections”).  
• Be sure your speakers can handle 25 watts per channel if 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 making the  
connections, disconnect the negative ( ) cable from your vehicle’s battery.  
-
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Note: After you complete the connections and reconnect the battery wire,  
you will need to reset all clock/timer/memory devices in your vehicle.  
REM  
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 12-  
volt battery power when the ignition is set to ON or ACC. This connection  
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.  
GND  
4. Connect the black wire’s spade connector to the amplifier’s  
terminal.  
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 not insulated from the chassis by a plastic part or  
other insulating material.  
+12V  
6. Connect the red wire’s spade connector to the amplifier’s  
terminal.  
7. Remove the nut from the battery’s positive ( ) terminal bolt, then place the  
+
red wire’s 10A fused eyelet terminal over the end of the bolt.  
Caution: Due to the amplifier’s high current requirement, you MUST con-  
nect the red wire’s fused end directly to the vehicle’s positive ( ) battery  
+
cable terminal or damage to your vehicle’s wiring could result.  
Note: Do not reconnect your vehicle battery’s negative ( ) cable yet.  
-
6
 
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CONNECTING YOUR AUTOSOUND SYSTEM  
Low Level Input Connections  
You can connect your autosound system’s low-level phono output jacks to the  
LOW INPUT  
amplifier’s  
phono jacks.  
Note: For a cleaner, less noisy signal transfer between your autosound system  
LOW INPUT  
and the amplifier, the amplifier’s  
phono jacks are gold-plated.  
For the best results, use shielded audio cables, such as Cat. No. 42-2368 (not  
supplied). If your autosound system has only two phono outputs, you will also  
need two shielded Y-adapter cables, such as Cat. No. 42-2435 (not supplied).  
1. Temporarily place the amplifier as close as possible to the selected mount-  
ing location.  
2. If your autosound system has four phono outputs and you are using four  
speakers, connect the autosound system to the amplifier using audio cables  
FRONT L  
FRONT R  
REAR L  
, rear-left to ,  
as follows: front-left to  
and rear-right to  
, front-right to  
REAR R  
:
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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-left to FRONT L and front-right to FRONT R, or  
• rear-left to REAR L and rear-right to REAR R  
8
 
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If your autosound system has only two phono output jacks (left and right)  
and you are using four speakers, first connect the single phono plug end of  
a Y-adapter shielded audio cable to each autosound system output jack.  
Then:  
• Connect the other two ends of the left Y-adapter to the amplifier’s corre-  
sponding FRONT L and REAR L phono jacks  
• Connect the other two ends of the right Y-adapter to the amplifier’s corre-  
sponding FRONT R and REAR R 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, simply connect them to the amplifier’s  
corresponding FRONT L and FRONT R, or REAR L and REAR R phono jacks.  
High-Level Input Connections  
If your stereo system has only speaker outputs, you can connect them to the am-  
plifier’s rear HIGH INPUT and front HIGH INPUT sockets using the floating ground  
connection or the common ground connection method.  
10  
 
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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 placed in their approximate locations, run one speaker wire  
from each speaker to the amplifier. We recommend you use 16- or 18-gauge  
marked or color-coded wires to help you correctly connect the speakers to your  
amplifier. For the maximum bass response and the best overall performance,  
keep your speakers properly phased (connect + to + and to ).  
- -  
Caution: Do not connect the speakers’ negative ( ) terminal wires to chassis  
-
ground.  
Note: Speaker wires have two conductors. Color-coded wires have a stripe run-  
ning down one of the conductors or different colored insulation for each conduc-  
tor. Your local Radio Shack store has a wide selection of speaker wire to choose  
from.  
Preparing the Speaker Wires  
1. Separate each speaker wire’s two conductors at both ends for a length of  
about 4 inches.  
1
2. Strip the insulation from the ends of each conductor to expose /4 inch of  
wire.  
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-  
fier’s FL (front-left negative) terminal.  
-
3. Repeat Steps 1 and 2 to connect a speaker wire to the amplifier’s FR (front-  
right) terminals.  
4. Repeat Steps 1 3 to connect speaker wires to the amplifier’s RL (rear-left)  
-
and RR (rear-right) terminals.  
5. Connect the other ends of the four speaker wires so FL connects to the  
front-left speaker, FR to the front-right speaker, RL to the rear-left speaker,  
and RR to the rear-right speaker.  
14  
 
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Connecting Two Speakers  
If you are connecting only two speakers, you can connect them to the amplifier’s  
front (FL and FR) or rear (RL and RR) speaker terminals.  
1. Connect one end of a speaker wire’s marked conductor to the amplifier’s  
FL (front-left positive) or RL (rear-left positive) terminal.  
+
+
2. Connect the end of the speaker wire’s unmarked conductor to the ampli-  
fier’s FL(front-left negative) or RL (rear-left negative) terminal.  
3. Repeat Steps 1 and 2 to connect a speaker wire to the amplifier’s FR and  
+
FR(front-right) or RR or RR (rear-right) terminals.  
+
4. Connect the other ends of the speaker wires so FL connects to the front-left  
speaker and FR to the front-right speaker, or RL connects to the rear-left  
speaker and RR connects to the rear-right speaker.  
15  
 
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TESTING THE CONNECTIONS  
Before you permanently mount the amplifier, temporarily reconnect your vehicle  
battery’s negative ( ) cable, turn your vehicle’s ignition to ON or ACC, then test  
-
the connections.  
The amplifier is properly connected to the autosound system and speakers if you  
can verify that the amplifier and the autosound system turn on properly and the  
speakers’ sound is clear and unmuffled.  
If you cannot quickly verify that all components operate properly, immediately  
turn off your vehicle’s ignition. Then disconnect your vehicle battery’s nega-  
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.”  
MOUNTING THE AMPLIFIER  
Before you begin mounting the amplifier, make sure you have the following sup-  
plied 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: Be careful to not drill into anything behind the mounting surface  
1. Temporarily disconnect your vehicle battery’s negative ( ) cable again.  
-
2. To make mounting more convenient, temporarily disconnect 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.  
9
4. Drill /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 sys-  
tem. 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 shorts. 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 vehicle’s  
ignition.  
1. Using a flat blade screwdriver, turn both LEVEL MIN/MAX controls fully coun-  
terclockwise to MIN.  
Note: The right level control is for the front speakers; the left level control is  
for the rear speakers.  
18  
 
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2. Temporarily turn up the autosound system’s volume control to about one-  
third 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 dis-  
tort. Then immediately turn down the volume to the point just below where  
distortion began.  
5. Adjust the level controls until 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.  
19  
 
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MAINTENANCE  
Your Optimus 4 × 25 Watt Trunk Mount Amplifier is an example of superior  
design and craftsmanship. The following suggestions will help you care for  
your amplifier so you can enjoy it for years.  
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 temperature envi-  
ronments. Temperature extremes can shorten the life of elec-  
tronic devices and distort or melt plastic parts.  
Handle the amplifier gently and carefully. Dropping it can  
damage circuit boards and cases and cause the amplifier to  
work improperly.  
Keep the amplifier away from dust and dirt, which can cause  
premature wear of parts.  
Wipe the amplifier with a damp cloth occasionally to keep it  
CLEANER  
looking new. Do not use harsh chemicals, cleaning solvents,  
or strong detergents to clean the amplifier.  
Modifying or tampering with the amplifier’s internal components can cause a  
malfunction and invalidate your amplifier’s warranty. If your amplifier is not per-  
forming as it should, take it to your local Radio Shack store for assistance.  
20  
 
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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.  
21  
 
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SPECIFICATIONS  
Output Power @ 14.4 VDC 1 kHz 10% THD  
Front .................................................................................................25W ¥ 2  
Rear..................................................................................................25W ¥ 2  
Frequency Response........................................................ 20–20,000 Hz (±3 dB)  
Input Impedance  
Low Input.......................................................................................10 kOhms  
High Input ......................................................................................100 Ohms  
Input Sensitivity (for 10% THD Output Power)  
Low Input...........................................................................................150 mV  
High Input ..............................................................................................2.5 V  
Power Supply Voltage............................DC 14.4V Negative Ground (10.5–16V)  
Maximum Current Draw .................................................................................10A  
Matching Speaker Impedance ............................................... 4 Ohms or Greater  
Fuse Requirement ........................................................................................10 A  
Dimensions ..........................................................21/4 ¥ 71/4 ¥ 81/4 Inches (HWD)  
..................................................................................... (53 ¥ 200 ¥ 210 mm)  
Net Weight ....................................................................................3.7 lbs (1.7 kg)  
Specifications are typical; individual units might vary. Specifications are subject  
to change and improvement without notice.  
22  
 
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NOTES  
23  
 
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RADIO SHACK LIMITED WARRANTY  
This product is warranted against defects for 1 year from date of purchase from Radio  
Shack company-owned stores and authorized Radio Shack franchisees and dealers.  
Within this period, we will repair it without charge for parts and labor. Simply bring your  
Radio Shack sales slip as proof of purchase date to any Radio Shack store. Warranty  
does not cover transportation costs. Nor does it cover a product subjected to misuse,  
accidental damage, alteration or improper installation.  
EXCEPT AS PROVIDED HEREIN, RADIO SHACK MAKES NO EXPRESS WARRAN-  
TIES AND ANY IMPLIED WARRANTIES ARE LIMITED IN DURATION TO THE DURA-  
TION OF THE WRITTEN LIMITED WARRANTIES CONTAINED HEREIN. Some states  
do not permit limitation or exclusion of implied warranties; therefore, the aforesaid limi-  
tation(s) or exclusion(s) may not apply to the purchaser.  
This warranty gives you specific legal rights and you may also have other rights which vary from  
state to state.  
We Service What We Sell  
9/94  
RADIO SHACK  
A Division of Tandy Corporation  
Fort Worth, Texas 76102  
7A5  
Printed in Taiwan  
 

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