INTRODUCTION
An audio AMP is basically a system which is used as a means of increasing the level of sound or audio signals for maximum use.
A public address system consists basically of microphone, Amplifier and speaker(s) to facilitate the communication to intelligible speech to groups of people or an audience. The main purpose of providing sound reinforcement indoors with sufficient high – fidelity being the coverage of large groups with unobstrusive sound system. Directional horns are often employed in outdoor systems to concentrate sound energy efficiently over the areas served. Intelligibility may be the performance criteria for an indoor system such as an air waiting room. On the other hand, high fidelity reproduction is required for sound reinforcement system for instance, a conference hall, or a class room.
Most power amplifiers of a public address system have provisions for one or more microphones and one or other sound sources such as FM, AM radio tuner output, tape recorder and record player generally tagged auxiliary sound sources. Level traders or volume contracts are provided to adjust the volume of each of those sources independently.
In this project, the concentration of a high fidelity (H1 – F1) power amplifier for the in public address system.
This amplifier is designed as a unit utilizing three input sources. Operating controls are provided for each input source with the possibility of mixing the three input sources depending on the setting of the operating or gain controls.
This flexibility of mixer operation is without sudden increase or decrease in volume.
CHAPTER ONE
LARGE SIGNAL AMPLIFIERS
1.1 POWER AMPLIFIERS
All amplifiers are power amplifiers. However those operating in the early stages of the signal processing system deal with small signals. These early stages are designed to give good voltage gain. Since voltage gain is the most important functions of these amplifiers, they are called voltage amplifiers. The set up of a simple audio amplifier large – signal stage and the speaker. The microphone produces a very small signal, in the millivolt range. The small – signal stage amplifiers this audio signal and it becomes larger. The larger signal. It is called a Power Amplifier.
A Power Amplifier is designed for good power gain. It must handle large voltage and current swings. These high voltages and currents, the power is high.