Radio Shack 32-2055 User Manual Download Page 9

16

The Basics

17

The Basics

exceed the amplifi er’s maximum impedance (16 ohms) or fall 
below the minimum impedance (4 ohms). You can achieve 
a proper total impedance by combining series and parallel 
connections.

A total speaker impedance higher than 16 ohms 
or lower than 4 ohms can damage your amplifi er 
or speakers. When determining the total speaker 
impedance, fi rst determine whether you are 
connecting the speakers in series, parallel, or a 
series/parallel combination.

preparing the speaker wires

Use the shortest length of wire possible to connect the 
speakers. After placing the speakers, use this table to 
determine the wire length and choose the appropriate gauge.

Wire Length

Wire Gauge

7.6m (25 ‘) or less

18 gauge

Over 7.6m (25‘)

16 gauge

To prepare the speaker wire, remove about 1/2 inch 
(12.5mm) of insulation from the end of the speaker wire you 
are connecting to the amplifi er. Then twist the exposed wire 
to secure all of the wire strands.

connecting two speakers in series

Speakers are connected in series when the fi rst speaker’s 
positive terminal is connected to the next speaker’s negative 
terminal.

Determine the total speaker impedance of speakers 
you want to connect in series by adding up 
the individual impedances of all the connected 
speakers.

For example

: If connecting two 4-ohm speakers in 

series, your total speaker impedance is 8 ohms.

NOTE

connecting speakers

You can connect one or more 4-, 8-, or 16-Ohm speakers to 
the amplifi er. To ensure equal volume from each speaker, all 
connected speakers should have the same impedance rating.

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 
signifi cantly decreased bass effect .

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. Phasing is correct when you c to + and 
- to -.

You can also bridge the amplifi er's channels. The amplifi er 
has two channels: A and B. If you connect two pairs of 
speakers, follow these guidelines:

•  Speakers connected to the same channel (A or B) are 

part of a pair and must be of the same impedance.

•  Speakers connected to different channels (A or B) are 

not part of a pair and can be different impedance.

determining total speaker impedance

Before you connect speakers to the amplifi er, you must 
determine the total speaker impedance. To determine total 
speaker impedance, you must fi rst decide if you are going 
to connect the speakers in series, parallel, or a series/parallel 
combination.

If you are connecting more than two speakers in series 
only or parallel only, be sure the total impedance does not 

Speaker 

Terminals

STEREO/MONO 

Switch

NOTE

Summary of Contents for 32-2055

Page 1: ... power you need in a professional sound system Its wide frequency response easily handles amplification of voice and music Use it anywhere you need to deliver special announcements with excellent sound It is perfect for meeting halls auditoriums sporting events schools or in the office for paging systems With a bridged speaker connection the amplifier can produce up to 350 watts of clean powerful sou...

Page 2: ...erating your amplifier 22 monitoring sound sources 23 listening safely 23 using the feedback filter 23 using the level meters and clipping indicator 24 CAUTION TO REDUCE THE RISK OF ELECTRIC SHOCK DO NOT REMOVE THE COVER OR BACK NO USER SERICEABLE PARTS INSIDE REFER SERVICING TO QUALIFIED PERSONNEL The lightning symbol is intended to alert you to the presence of uninsulated dangerous voltage within ...

Page 3: ... amplifier resets itself when the problem is corrected A B Speaker Switch Select the speakers you want to use with the amplifier in Channel A Channel B or both for use with 8 ohm speakers only MIC 1 MIC 2 and MIC 3 Adjust volume for the connected microphones MIC 4 PHONO Adjust volume of connected microphone MIC 4 or turntable FEEDBACK FILTER Turn to control audio feedback Volume Control Left Right s...

Page 4: ...igh level sound source for music or special effects EQ BYPASS Selector Select EQ if you are using an equalizer or BYPASS if you are using another external processor STEREO MONO Selector Select bridged mono input mode in combination with a mono signal source plugged into the left channel Speaker Terminals Connect two sets of speakers Left and Right for A and B Audio Input Jacks Connect input source...

Page 5: ...re or electric shock 16 Never push objects of any kind into this appliance through openings as they may touch dangerous voltage points or short out parts that could result in a fire or electric shock Never spill liquid of any kind on the appliance important safety instructions UL 6500 1 Read all safety and operating instructions before the appliance is operated 2 Keep all safety and operating instr...

Page 6: ...ons Adjust only those controls that are covered by the operating instructions as an improper adjustment of other controls may result in damage and will often require extensive work by a qualified technician to restore the appliance to normal operation If the appliance has been dropped or damaged in any way When the appliance exhibits a distinct change in performance 19 Do not attempt to service thi...

Page 7: ...ont of amplifier is out and AC power cord is not plugged in connecting microphones You can connect up to four high or low impedance microphones to the microphone inputs on the back of the amplifier Each input labeled MIC1 MIC2 MIC3 and MIC4 has a balanced and unbalanced jack You need a microphone with a inch 6 35mm plug to connect to an unbalanced jack or a microphone cord with a 3 pin XLR plug to c...

Page 8: ...from an outside equalizer They do not handle the signal from this equalizer s stereo INPUT jacks NOTE CD AUX Jack MIX BUS Jack EQ IN OUT Jacks If your microphone cord is longer than 20 feet 6 meters we recommend that you connect it to a balanced jack to reduce signal hum If you connect a microphone to both balanced and unbalanced jacks for MIC1 MIC2 MIC3 or MIC4 the microphone you connect to the u...

Page 9: ...ur total speaker impedance is 8 ohms NOTE connecting speakers You can connect one or more 4 8 or 16 Ohm speakers to the amplifier To ensure equal volume from each speaker all connected speakers should have the same impedance rating 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 h...

Page 10: ...on Use this connection if you are connecting more than one speaker on the same channel or if you do not have high power speakers 1 Connect the speaker wires to the corresponding left and right positive and negative speaker terminals 2 Connect the other end of the left and right speaker s positive and negative wires to the amplifier s corresponding SPEAKER LEFT and SPEAKER RIGHT terminals for each c...

Page 11: ...ction Use this connection if you have high power speakers that can handle a power output of 350 Watts For a bridged connection do not connect any speaker wire to the black SPEAKER terminals 1 Connect the speaker wires to the speaker s positive and negative terminals 2 Connect the other end of the speaker s positive and negative wires to the amplifier s red SPEAKER LEFT and SPEAKER RIGHT terminals S...

Page 12: ...C2 MIC3 MIC4 PHONO and CD AUX turn on the amplifier and any connected sound sources If you hear any feedback turn FEEDBACK FILTER clockwise until you reduce or eliminate the feedback The FEEDBACK FILTER control decreases feedback frequencies by up to 12dB If it does not eliminate the feedback try using a frequency equalizer to further decrease the feedback frequencies NOTE PHONES Jack operating you...

Page 13: ... Holder Cap NOTE NOTE using the level meters and clipping indicator The illuminating flow of the output LED indicators reflect the amplifier s output level The stronger the signal the more LEDs illuminate The maximum signal through the MPA 250 should cause the CLIPPING LED to blink at peak music levels using speaker A B Press in SPEAKER A or SPEAKER B on the front of the amplifier for the channel you ...

Page 14: ...se until you reduce or eliminate feedback Your microphones or speakers could be too close together Reposition the microphones and speakers product specifications Input Impedance 20k Ohms Continuous Output Power Stereo at 1 kHz 125 Watts x 2 8 Ohms Stereo at 1 kHz 175 Watts x 2 4 Ohms Bridged at 20 Hz to 20 kHz 250 Watts 8 Ohms Bridged at 1 kHz 350 Watts 8 Ohms Total Harmonic Distortion 70 Watts 8 O...

Page 15: ...00 Taylor Street 6th Floor Fort Worth TX 76102 04 04 Keep the amplifier dry If it gets wet wipe it dry immediately Use and store the amplifier only in room temperature environments Handle the amplifier carefully do not drop it Keep the amplifier away from dust and dirt and wipe it with a soft cloth occasionally to keep it looking new If your amplifier is not performing as it should take it to your Radi...

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