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 PAGEi
APPROVAL PAGEii
DEDICATIONiii
ACKNOWLEDGEMENTiv
CHAPTER ONE
1.0BACKGROUND STUDY/INTRODUCTION1
1.1 AIMS AND OBJECTIVES OF STUDY 3
1.2SIGNIFICANT OF STUDY4
1.3SCOPE OF STUDY5
CHAPTER TWO
2.0LITERATURE REVIEW7
2.1RESISTORS 7
2.2CAPACITORS9
2.3TRANSFORMER12
2.4OPERATIONAL AMPLIFIER16
2.5MICROPHONE17
2.6PRE-AMP20
2.7POWER-AMP21
CHAPTER THREE
3.0SYSTEM OPERATION22
3.1CIRCUIT DIAGRAM22
3.2BLOCK DIAGRAM23
3.3OPERATION PRINCIPLE23
CHAPTER FOUR
4.0SYSTEM CONSTRUCTION AND PACKAGING24
4.1PHOTOTYPING24
4.2COMPONENT MOUNTING25
4.3SOLDERING26
4.4TESTING27
CHAPTER FIVE
5.0SYSTEM TESTING 28
5.1CONTINUITY TESTING28
5.2VOLTAGE TESTING29
5.3TESTING WITH OSCILLOSCOPE29
CHAPTER SIX
6.0CONCLUSION AND RECOMMENDATION31
6.1CONCLUSION31
6.2RECOMMENDATION32
REFERENCE36