Radio Shack 32-2001, 811081640B, MPA-40, 02A00 User Manual
MPA-40 20-Watt PA Amplifier
32-2001.fm Page 1 Friday, February 4, 2000 7:53 AM
Owner’s Manual
Please read before using this equipment.
32-2001.fm Page 2 Friday, February 4, 2000 7:53 AM
ˆ
Contents
Features ................................................................................................................... 3
Preparation .............................................................................................................. 4
Presetting the Controls ....................................................................................... 4
Choosing a Location .................... .... ... ....................................... ... ...................... 4
Making Connections ............................................................................................... 4
Speakers .................................................................................................................. 5
Speaker Phasing ................................................................................................ 5
Determining Total Speaker Impedance .............................................................. 6
Connecting Speakers .................. .... ... ... ... ....................................... ... .... ... ......... 7
One Speaker ................................................................................................ 7
Two or More Speakers Without Transformers .......... ................................... 7
Multiple Speakers with Transformers ........................................................... 9
Controls and Operation ........................................................................................ 11
Troubleshooting .................................................................................................... 12
Care and Maintenance .......................................................................................... 13
Replacing Fuses ................. ... ... ... .... ... ....................................... ... .................... 13
DC Cable .................................................. ....................................... ... ... ... . 13
Amplifier ..................................................................................................... 13
Specifications .......................... .......................... ...................... ....................... ....... 14
Notes ...................................................................................................................... 15
2000 Tandy Corporation.
©
RadioShack and RadioShack.com are registered trademarks used by Tandy Corporation.
2
All Rights Reserved.
32-2001.fm Page 3 Friday, February 4, 2000 7:53 AM
ˆ
Features
Your RadioShack 20-Watt PA Amplifier
gives you 20 watts of solid power for
your PA system. Its wide frequency response easily handles amplification of
voice and music. It operates on either
120 volts AC or 12 volts DC power so
you can use it anywhere you want to deliver special announcements or play music with great sound.
Its features include:
Microphone Jacks
— let you connect
up to two dynamic microphones.
Input Jacks
— let you connect auxiliary
equipment, such as a CD player, tape
deck, or receiver, for music and special
effects.
Individual Microphone Controls —
let
you separately adjust the volume of
each microphone.
Master Volume Control
— lets you ad-
just the overall sound level.
Auxiliary Volume Control
— lets you
adjust the volume of the connected
equipment.
Tone Control
— lets you customize the
sound to suit your personal preferences,
depending on the acoustics, speakers,
and sound source.
Your amplifier is ETL listed to UL standards and meets all applicable FCC
standards.
WARNING
: To reduce the risk of fire
or shock hazard, do not expose this
product to rain or moisture.
CAUTION
RISK OF ELECTRIC SHOCK.
DO NOT OPEN.
CAUTION
ELECTRIC SHOCK, DO NOT REMOVE
COVER OR BACK. NO USER-SERVICEABLE PARTS INSIDE. REFER SERVICING
TO QUALIFIED PERSONNEL.
!
: TO REDUCE THE RISK OF
This symbol is intended to
alert you to the presence of
uninsulated dangerous voltage within the product’s
enclosure that might be of sufficient magnitude to constitute a risk of electric shock.
Do not open the product’s
case.
This symbol is intended to
inform you that important
operating and maintenance
instructions are included in
the literature accompanying
this product.
!
Five Speaker Terminals
speaker connection easy.
— make
3
32-2001.fm Page 4 Friday, February 4, 2000 7:53 AM
ˆ
Preparation
PRESETTING THE
CONTROLS
Warning:
amplifier could damage your hearing or
the speakers connected to the amplifier’s output.
To avoid accidentally overdriving a
channel or prematurely amplifying an
audio input, set all the amplifier’s frontpanel controls to their lowest settings.
ˆ
A sudden high output from the
Making Connections
To avoid sudden audio from the input
sources, be sure all audio devices are
turned off before you connect them to
the amplifier.
CHOOSING A LOCATION
Choose a location with adequate ventilation. Do not place the amplifier on thick
carpeting or cushions (which can restrict
the air flow) or near a heat sour ce, such
as a heat vent or radiator (which can
cause the amplifier to overheat).
Be sure you connect all auxiliary equipment
and speakers before connecting and turning on
power.
AUX/CD Input Jack
high-level sound source (such as a tape
deck, CD player, or receiver). To connect a stereo audio source to this ja ck,
use a shielded Y-adapter (not supplied;
available at your local RadioShack
store).
PHONO Input Jack
ble with a moving magnetic cartridge. To
4
— connect any
— connect a turnta-
avoid sound distortion, do not connect a
high-level audio input source to this jack.
GROUND Screw
wire (usually black or green) from your
turntable to this screw to avoid a low-frequency hum. You can also use this
screw to ground any other system connection.
— connect the ground
32-2001.fm Page 5 Friday, February 4, 2000 7:53 AM
PHONO/AUX/CD Switch
input source. Even if you connected
auxiliary equipment to both the
AUX/CD
and
only one source at a time.
Speaker Push Terminals
appropriate tab to open a terminal. Insert the end of a speaker wire into the
opening, then release the tab to close
the terminal and secure the wire (see
“Connecting Speakers” on Page 7).
AC Power Cord
simply plug this attached cord into a
standard AC outlet.
4A/12V (4-Amp/12-Volt DC Power)
Jack
— connect the supplied DC power
ˆ
input jacks, you can use
— to use AC power,
Speakers
— select the
PHONO
— press the
SPEAKER PHASING
Phasing is the direction the speaker
cone moves with reference to the pola rity of the connection wires. Proper phasing is important when you use more than
one speaker in the same room or area.
Out-of-phase speakers can lose up to
one-half of their potential volume, and
can have a significantly decreased bass
effect.
Speakers are in phase if all the speaker
cones move in the same direction when
an equal signal is applied. Phasing is
correct if you observe the correct polarity (+ to + and – to –) when connecting
the speakers.
cable’s barrel plug to this jack if you
want to temporarily power the amplifier
from your vehicle’s 12-volt ba ttery . Then
connect the cable’s other end to your
vehicle’s 12-volt accessory sock et (such
as a cigarette-lighter socket).
Cautions:
• Your vehicle must have a negativeground electrical system. If you are
not sure it does, check with your
vehicle dealer.
• Unplug the AC power cord before
you connect the DC power cable.
Likewise, disconnect the DC power
cable before you plug in the AC
power cord.
Most speaker terminals are color-coded
or have a mark that indicates the terminal’s polarity. Usually, terminals with
positive polarity are red or have a plus
symbol (+), and terminals with negative
polarity are black or have a minus symbol (–). If the speaker terminals ar e unmarked, follow these steps to determine
their polarity.
1. Remove about 1 inch of insulation
from both ends of a short piece of
wire (not supplied; available at your
local RadioShack store). Then twist
the exposed wire to secure all its
strands.
2. Connect one end of the wire to one
of the speaker terminals.
5
Loading...