Radio Shack 85 User manual

Cat. No. 12-1977
OWNER’S MANUAL
Please read before using this equipment.
85 ×4 Hi
g
h Power 4-Channel
Trunk Mount Amplifier
12-1977.fm Page 1 Tuesday, July 13, 1999 10:07 AM

2
FEATURES
Your Optimus 85 ×4 High Power 4-
Channel Trunk Mount Amplifier is de-
signed to produce a total of 340 watts
to give added punch and power to
your vehicle’s existing stereo sys-
tem.
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 sounds
but not lose the other sounds or pow-
er. 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 -let you
connect low-level (pre-amplifier) sig-
nal inputs to match your autosound
system’s output for the best high-fi-
delity performance.
14k Gold-Plated Speaker Termi-
nals -designed for low impedance,
high conductivity, and minimum cor-
rosion to provide the highest signal
transfer and lowest sound distortion.
Input Level Controls -let you adjust
the level of the audio signals that en-
ter the amplifier.
Automatic Power Switchin
g
-auto-
matically turns on/off the amplifier
when you turn on/off your autosound
system.
Brid
g
in
g
Capabilit
y
-lets you com-
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 each chan-
nel.
Crossover Frequenc
y
Circuit -lets
you adjust the crossover frequency
from 45-400 Hz for both channels
three and four when you use only two
speakers.
Crossover Frequenc
y
ON/OFF
Switch -lets you set the amplifier to
drive a connected subwoofer.
Automatic Thermal Protection
S
y
stem (ATPS) -automatically low-
ers the amplifier’s output power
when the amplifier’s internal temper-
ature reaches 202×F then increases
the output power when the amplifier
cools down.
© 1995 Tandy Corporation.
All Rights Reserved.
Optimus and Radio Shack are registered trademarks used by Tandy Corporation.
12-1977.fm Page 2 Tuesday, July 13, 1999 10:07 AM

3
Mute Turn On Circuit -eliminates
the irritating thump noise that some
amplifiers produce when you turn
them on.
Power Indicator -lights when power
is on.
Full MOSFET Power Supply -pro-
duces enough power to supply the
main amplifier and has a consider-
able amount of reserve power for
peak “high demand” situations.
Short Circuit Protection -distorts
sound if any output channel shorts so
you can know to turn off the amplifier.
Important: Be sure your speakers
can handle 340 watts of power (170
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 an impedance of
at least 4 ohms. Your local Radio
Shack store carries a full line of
speakers.
Note: If the connectors on your vehi-
cle stereo system are not compatible
with the amplifier’s connectors, your
local Radio Shack store sells adapter
harnesses for many vehicles.
12-1977.fm Page 3 Tuesday, July 13, 1999 10:07 AM

4
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
12-1977.fm Page 4 Tuesday, July 13, 1999 10:07 AM

5
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.
Warnin
g
: 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.
12-1977.fm Page 5 Tuesday, July 13, 1999 10:07 AM

6
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 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 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.
Note: After you complete the connections and reconnect the battery wire,
you will need to reset all clock/timer/memory devices in your vehicle.
12-1977.fm Page 6 Tuesday, July 13, 1999 10:07 AM

7
2. Securely connect the supplied dark
blue/white wire’s spade connector end
to the amplifier’s REM (remote power)
terminal.
3. Connect the dark blue/white wire’s
other end to your autosound system’s
switched power lead using a twist-on
terminal connector (such as Cat. No.
64-3057, not supplied).
Note: If your autosound system does not have a remote power output lead,
connect this wire to a point in your vehicle’s fuse box 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.
4. Connect the black wire’s eyelet/spade terminal end to the amplifier’s two
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.
Note: Be sure the bolt is not insulated from the chassis by a plastic part or
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
current requirement, you MUST con-
nect the red wire’s fused end directly
to the vehicle’s positive (+) battery
cable terminal bolt or damage to your
vehicle’s wiring could result.
Note: Do not reconnect your vehicle battery’s negative (–) cable yet.
(illus - please add a
dwg that illustrates
step 7)
(illus -please adda
dwg that illustrates
step 3)
12-1977.fm Page 7 Tuesday, July 13, 1999 10:07 AM

8
CONNECTING TO YOUR AUTOSOUND SYSTEM
Low Level Input Connections
You can connect your autosound system’s low-level phono output jacks to the
amplifier’s low-level phono input jacks. For the best results, use shielded audio
cables, such as Cat. No. 42-2368 (not supplied).
Note: For a cleaner, less noisy signal transfer between your autosound system
and the amplifier, the amplifier’s low input phono jacks are gold-plated.
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
as follows: front-left to CH1, front-right to CH2, rear-left to CH3, and rear-right
to CH4.:
12-1977.fm Page 8 Tuesday, July 13, 1999 10:07 AM

9
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 CH1 and front-right to CH2, or
• rear-left to CH3 and rear-right to CH4
12-1977.fm Page 9 Tuesday, July 13, 1999 10:07 AM

10
If your autosound system has only two phono output jacks (left and right)
and you are using four speakers, use two Y-adapter audio cables to make
the connections as follows:
Note: For the best results, use shielded phono plug-to-phono plug Y-
adapter audio cables, such as Cat. No. 42-2368 (not supplied).
• Connect one of the Y-adapter’s double phono plug ends to the amplifier’s
CH1 phono jack.
• Connect the other double phono plug end to the amplifier’s CH3 phono
jack.
• Connect the single phono plug end to the autosound system’s left output
jack.
• Connect one of the other Y-adapter’s double phono plug ends to the
amplifier’s CH2 phono jack.
• Connect the other double phono plug end to the amplifier’s CH4 phono
jack.
• Connect the single phono plug end to the autosound system’s right out-
put jack.
12-1977.fm Page 10 Tuesday, July 13, 1999 10:07 AM