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Design And Construction Of 20watts Wireless Public Address System
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In this project, the audio amplifier used is capable of delivering
20watts continuously. The term “power amplifier†is a relative term with
respect to the amount of power delivered to the load and/or sourced by
the supply circuit.
In general a power amplifier is designated as the
last amplifier in a transmission chain (the output stage) and is the
amplifier stage that typically requires most attention to power
efficiency. Power amplifiers have also become lighter, smaller, more
powerful and more efficient due to increasing use of Class A amplifiers,
which offer significant weight and space savings as well as increased
efficiency.
Power amplifier circuits (output stages) are classified
as A, B, AB and C for analog designs, and class D and E for switching
designs, based upon the conduction angle or angle of flow, Θ, of the
input signal through the output amplifying device, that is, the portion
of the input signal cycle during which the amplifying device conducts.
The image of the conduction angle is derived from amplifying a
sinusoidal signal. (If the device is always on, Θ = 360o.) In this
project a class A amplifier is used because it offers low signal
distortion.
Loudspeaker is an electro-acoustical transducer that
converts an electrical signal to sound. A transducer that turns an
electrical signal into sound waves is the functional opposite of a
microphone.
Since a conventional speaker is constructed much like a
dynamic microphone, (with a diaphragm, coil and magnet), speakers can
actually work “in reverse†as microphones. The speaker pushes a medium
in accord with the pulsations of an electrical signal, thus causing
sound waves to propagate to where they can then be received by the ear.
The loudspeaker used in this project is a load of 8 Ohms.
1.2 AIMS AND OBJECTIVES
Public
speaking is the process of speaking to a group of people in a
structured, deliberate manner intended to inform, influence, or
entertain the audience. In public speaking, as in any form of
communication, there are five basic elements, often expressed as “who is
saying what to whom using what medium with what effects?â€(W.Kleitz;2005
pg134).
The major objective of this project is to design and
construct a public address system with relatively unique operational
characteristics that is capable of delivering 20 watts of electrical
power into an 8 Ohms load (loudspeaker). This will be achieved with
adequate tone controls and mixer stages so as to enable communication or
reproduction of speech and recorded music in buildings and
institutions.
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ABSRACT - [ Total Page(s): 1 ]It has become inevitable that there would be communication and due to the inherent limitation of the human voice, the public address system came to being. A public address or “P.A SYSTEM†is an electronic amplification system with a mixer ,amplifier and loudspeakers, used to reinforce a given sound , e.g a person making a speech, pre-recorded music ,or message and distributing the sound throughout a venue . The voice signal is passed through a microphone , which converts the sound en ... Continue reading---
