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
1.1 AIMS AND OBJECTIVES OF STUDY 3
1.2SIGNIFICANT OF STUDY4
1.3SCOPE OF STUDY5
4.0SYSTEM CONSTRUCTION AND PACKAGING24
5.0SYSTEM TESTING 28
5.3TESTING WITH OSCILLOSCOPE29
6.0CONCLUSION AND RECOMMENDATION31
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