Instruction/ maintenance manual of the product MPA-40 Radio Shack
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Owner’s Manual Please read before using this equ ipment. MPA-40 20-Watt PA Amplifier 32-2001.fm Page 1 Friday, February 4, 2000 7:53 AM.
2 ˆ Contents Features ......... ................ ................ ................ ................. ................ ................ ......... 3 Preparation ....... ................ ................ ............. ................. ................ .
3 ˆ Features Your RadioShack 20-Watt PA Amplifier gives you 20 watts of solid power for your PA system. Its wide frequen cy re- sponse easily handles amplification of voice and music. It operates on eithe r 120 volts AC or 12 volts DC power so you can use it anywhere you want to de- liver special announcement s or pl ay mu- sic with great sound.
4 ˆ Preparation PRESETTING THE CONTROLS Warning: A sudde n high out put from the amplifier could dama ge your hearing or the speakers conn ected to the amplifi- er’s output. To avoid accidentally overdr iving a channel or premat urely amplifying an audio input, se t all the amplifier’s front- panel controls to their lowest set tings.
5 PHONO/AUX/CD Switch — s elect the input source. Even if you connected auxiliary equipment to both the PHONO and AUX/CD input jacks, you can use only one so urce at a time . Speaker Push Termina ls — press the appropriat e tab to open a ter minal.
6 3. T ouch the positive end of a 1 .5-volt flashlight batt ery to the speake r ter- minal that does no t have the wire attached to it. 4. T ouch the negative end of the bat- tery with the lose end of the wire attached to the other speak er termi- nal.
7 • If you connect more t han two speak- ers using only se ries or only parallel connections, t he total impedance might exceed the am plifier ’s maxi- mum impedance (1 6 ohms) or fall below its minim um impedan ce (4 ohms). For example, if y ou connect fo ur 8- ohm speakers: –In series, the tota l impedance is 32 ohms (8 + 8 + 8 + 8 = 32).
8 you can make the correct connecti on. The total impedance of all the speakers must match one of the amplifier’s out put terminals ( 4 Ω , 8 Ω , or 16 Ω ) . Speakers in Series 1. T o determine the total impeda nce of speakers connecte d in series, add the impeda nce of all the speakers.
9 If you connect fou r 8-ohm speaker s in series, the total imp edance is 32 ohms (8 + 8 + 8 + 8 = 32). This exceeds the maximum rating. If you connect th ese speakers in paral- lel, the total impeda nce is 2 ohms (8 ÷ 4 = 2). This falls below the minimum rat- ing.
10 You need a separa te transformer for each spea ker. Line transformer s have several connec- tors called taps. The primary t aps (on one side o f the transformer) a re the inputs an d are rate d in watts. The secondary taps (on the op - posite side of t he transforme r) are the outputs and ar e ra te d in oh m s.
11 3. Connect a wire fr om the speaker ’s positive (+) terminal t o the trans- former’s secondary tap that matches the speaker ’s total imped- ance (4, 8, or 16 oh ms). 4. Connect a wire from the speaker ’s negative (–) te rminal to the COM tap on the transfor mer ’s seco ndary side.
12 ˆ T roubleshooting If you should ru n into difficulties, che ck the wiring of the system. Are the re any short circuits in th e speaker wirin g? Have you provided adequate ventila - tion? Did you calculate speaker imped- ance corr ectly? Be sure microphon es and connecting cables are not defective.
13 ˆ Care and Maintenance To enjoy yo ur amplifie r for a lon g time: • Keep the a mplifier dry . If it get s wet, wipe it dry immediately . • Use and store the amplifier only in normal tem perature environments. • Han dle the amplifier gently and carefully .
14 ˆ Specifications Output Power at 1 kHz, 10% THD ................. ................ .............. ................. .............. . 20 W atts THD at 1W , 1 kHz Low-Pass Filter MIC1 .......... .............. .............. .............. .........
15 ˆ Notes 32-2001.fm Page 15 Friday, February 4, 2000 7:53 AM.
32-2001 81 10816 40B 02A00 Printed in China RadioShack A Division of Ta ndy Corporation Fort Worth, Texas 76102 Limited One-Y ear Warranty This product is warranted by RadioShack against manufactu rin.
An important point after buying a device Radio Shack MPA-40 (or even before the purchase) is to read its user manual. We should do this for several simple reasons:
If you have not bought Radio Shack MPA-40 yet, this is a good time to familiarize yourself with the basic data on the product. First of all view first pages of the manual, you can find above. You should find there the most important technical data Radio Shack MPA-40 - thus you can check whether the hardware meets your expectations. When delving into next pages of the user manual, Radio Shack MPA-40 you will learn all the available features of the product, as well as information on its operation. The information that you get Radio Shack MPA-40 will certainly help you make a decision on the purchase.
If you already are a holder of Radio Shack MPA-40, but have not read the manual yet, you should do it for the reasons described above. You will learn then if you properly used the available features, and whether you have not made any mistakes, which can shorten the lifetime Radio Shack MPA-40.
However, one of the most important roles played by the user manual is to help in solving problems with Radio Shack MPA-40. Almost always you will find there Troubleshooting, which are the most frequently occurring failures and malfunctions of the device Radio Shack MPA-40 along with tips on how to solve them. Even if you fail to solve the problem, the manual will show you a further procedure – contact to the customer service center or the nearest service center
