INTRODUCTION
A public address system is an electronics sound amplification and distribution system with a microphone, amplifier and loud speaker used to allow a person to address a large public. The public address system consists of three main parts namely, the microphone (input transducer), amplifier and the loudspeaker (output transducer).
The microphone picks up the sound and convert it to electronic signal in milivolts and this is fed to the amplifier for amplification. In this project, a dual operational amplifier (OP-Amp) 1458 IC is used for the amplifications. The amplifier has two sections; the Pre-Amp and the power –AM. The pre-amp does the first boosting of the input audio signal to a level handleable by the last stage of the amplifier called power amp. This early stage (pre-amp) is designed to give good voltage gain. Hence the pre-amp is referred to as the voltage amplifier. The last amplifier stage is the power amp and is the stage that typically requires most attention; the power efficiency.
After the amplifier stage, the very small input signal is then magnified to a larger version and is fed to the speaker for conversion to sound. The speaker is an electromagnetic device that operates on the principle of electromagnetic induction and with the help of its component converts electrical signal to sound.
TABLE OF CONTENTS
TITLE PAGE i
APPROVAL PAGE ii
DEDICATION iii
ACKNOWLEDGEMENT iv
CHAPTER ONE
1.0 BACKGROUND STUDY/INTRODUCTION 1
1.1 AIMS AND OBJECTIVES OF STUDY 3
1.2 SIGNIFICANT OF STUDY 4
1.3 SCOPE OF STUDY 5
CHAPTER TWO
2.0 LITERATURE REVIEW 7
2.1 RESISTORS 7
2.2 CAPACITORS 9
2.3 TRANSFORMER 12
2.4 OPERATIONAL AMPLIFIER 16
2.5 MICROPHONE 17
2.6 PRE-AMP 20
2.7 POWER-AMP 21
CHAPTER THREE
3.0 SYSTEM OPERATION 22
3.1 CIRCUIT DIAGRAM 22
3.2 BLOCK DIAGRAM 23
3.3 OPERATION PRINCIPLE 23
CHAPTER FOUR
4.0 SYSTEM CONSTRUCTION AND PACKAGING 24
4.1 PHOTOTYPING 24
4.2 COMPONENT MOUNTING 25
4.3 SOLDERING 26
4.4 TESTING 27
CHAPTER FIVE
5.0 SYSTEM TESTING 28
5.1 CONTINUITY TESTING 28
5.2 VOLTAGE TESTING 29
5.3 TESTING WITH OSCILLOSCOPE 29
CHAPTER SIX
6.0 CONCLUSION AND RECOMMENDATION 31
6.1 CONCLUSION 31
6.2 RECOMMENDATION 32
REFERENCE 36
