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This project involved design and construction of an audio amplifier .The term audio refers to sound or human hearing as the range of human hearing extends from about 20 hertz to 20,000 hertz (i.e. 20k hertz) but varies considerably with age and individuals. That is we can hear air pressure change or vibration that vary in pitch from about 20 times per second to about 20,000 times per second.

The term pitch describes the subjective sensation of hearing an air pressure vibration or sound meaning pitch of a double bass is low, that is flute or soprano is high. The more the air pressure vibrates pre second, the higher the pitch.

Transistor which has the ability to amplify cannot amplify the air pressure (acoustic) directly; therefore it is necessary to first convert the air pressure vibration into equivalent electrical vibration by means of a sound transducer, a microphone or similar acoustic electrical transducer. Meaning that if one sings into a microphone, a pure tone that has a pitch say 1000 vibration per second will be gotten. The microphone output will be an electrical AC signal that has lets say about frequency of 15,000 hertz after passing through the amplifier circuit.

Amplifier circuit is the interconnection of diodes, capacitors resistors, transformers, integrated circuits, transistors, heat Zink each of which has a required function. The circuit is capable of amplifying a very weak signal to a larger signal.

For amplifier circuit to be able to drive more load (speakers), a good number of pair of transistors has to be used. Hence, the number of pair of transistor should not be too much to avoid humming.

Aim and Objectives

The main aim and objective of this project work is to design an audio amplifier system which can be used to amplify a very weak signal to produce a higher output so that it drives a number of loud speakers.

Scope of Study and Limitation

This project work is the design and construction of audio amplifier that could be able to drive a higher number of loads i.e. speakers with good impedance matching, with good volume.

The limitation is that, it is just an audio amplifier without any application like

  • Audio amplifier with mixer
  • Equalizers using operational amplifier
  • Photo voltaic light sensors using operational amplifier
  • Medical electronic monitoring system using operational amplifier
  • Phase detector using operational amplifier
  • Electronic thermometer using operational amplifier and so on.


This project work is relevant to the needs of the department, school, churches, mosques, and the society at large. It is useful in a congregation where it is used to raise the voice of the speaker so that he/she could be heard louder and clearer by the congregation. It can also be used to raise the volume of music and sound, during programme like NASTES, which as a result reduce stress and cost. This project is worthwhile, and stands to benefit many.



This project involved design and construction of an audio amplifier that could drive a quite number of speakers. This was achieved by coupling different stages of amplification together with a coupling element where the output of one stage serves as input to the next stage. The stages are, Pre-amplifier stage, Mixer Stage, Volume Control Stage, power output stage. This construction work resulted into an audio amplifier which can be used in Radio Receiver, Cassette Players, Video Players, Public Address System.  An audio amplifier is a device for increasing the power of a signal (i.e. makes sound louder and signal level greater). It does this by taking power from the power supply and controlling the output to match the input signal shape but with large amplitude.  A signal can be large in terms of it’s voltage level, current level or both, but in electronic system, a speaker requires several watts for good volume.


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