Design And Construction Of An Audio Equalizer Amplifier

ABSTRACT

This work is on audio equalizer. An equalizer allows the sound in specified frequency bands to be amplified or reduced, in order to adjust the quality and character of the sound. There are different types of equalizer for various uses, such as the parametric equalizers that are controlled using the knobs built into each mixer channel, or the graphic equalizers that allow multiple frequency bands to be adjusted using sliders. Rarely are the sounds of microphones and instruments that are input to the mixer perfect for delivery as-is to the venue. When mixing music that involves many instruments, some parts may inevitably be difficult to pick out. In this situation, adjusting only volume and panning is not sufficient, and equalizers can be used to adjust each frequency band to make the best characteristics of each instrument stand out. This work focuses on the graphic equalizer which allows multiple frequency band control in audio system.

TABLE OF CONTENTS

COVER PAGE

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWELDGEMENT

ABSTRACT

CHAPTER ONE

• INTRODUCTION
• BACKGROUND OF THE PROJECT
• OBJECTIVE OF THE STUDY
• PURPOSE OF THE PROJECT
• APPLICATION OF THE PROJECT
• LIMITATION OF THE PROJECT
• SCOPE OF THE PROJECT
• METHODOLOGY
• PROJECT ORGANISATION

CHAPTER TWO

LITERATURE REVIEW

• AN OVERVIEW OF AN AUDIO EQUALIZATION
• HISTORICAL BACKGROUND OF THE PROJECT
• TYPES OF FILTER
• GENERAL APPLICATION OF THE PROJECT

CHAPTER THREE

METHODOLOGY

• SYSTEM BLOCK DIAGRAM
• SYSTEM CIRCUIT DIAGRAM
• CIRCUIT COMPONENTS DESCRIPTION
• SYSTEM OPERATION
• CIRCUIT DESCRIPTION
• COMPONENTS LIST
• DESCRIPTION OF MAJOR COMPONENTS USED

CHAPTER FOUR

TEST AND RESULT ANALYSIS

• CONSTRUCTION PROCEDURE AND TESTING ANALYSIS
• CASING AND PACKAGING
• ASSEMBLING OF SECTIONS
• TESTING OF SYSTEM OPERATION

CHAPTER FIVE

• CONCLUSION
• RECOMMENDATION
• REFERENCES

CHAPTER ONE

1.0                                                        INTRODUCTION

An equalizer allows the sound in specified frequency bands to be amplified or reduced, in order to adjust the quality and character of the sound. There are different types of equalizer for various uses, such as the parametric equalizers that are controlled using the knobs built into each mixer channel, or the graphic equalizers that allow multiple frequency bands (such as 7, 15, or 31 bands) to be adjusted using sliders (knob).

In general, the most commonly used equalizers are the parametric equalizers equipped on each channel of the mixer.

In general, graphic equalizers are connected to the mixer outputs to adjust the overall tone of the sound, or to correct feedback problems. The frequency bands of a graphic equalizer are finely divided up, and sliders are used to boost (by moving the slider up) or cut (by moving the slider down) each frequency range.
Rarely are the sounds of microphones and instruments that are input to the mixer perfect for delivery as-is to the venue. When mixing music that involves many instruments, some parts may inevitably be difficult to pick out. In this situation, adjusting only volume and panning is not sufficient, and equalizers can be used to adjust each frequency band to make the best characteristics of each instrument stand out.

1.1                                         BACKGROUND OF THE PROJECT

The concept of equalization was first applied in correcting the frequency response of telephone lines using passive networks; this was prior to the invention of electronic amplification. Initially equalization was used to “compensate for” (i.e. correct) the uneven frequency response of an electric system by applying a filter having the opposite response, thus restoring the fidelity of the transmission. A plot of the system’s net frequency response would be flat, as its response to all frequencies would literally be equal. Hence the term “equalization.”

Much later the concept was applied in audio engineering to adjust the frequency response in recording, reproduction, and live sound reinforcement systems. Sound engineers correct the frequency response of a sound system so that the frequency balance of the music as heard through speakers better matches the original performance picked up by a microphone. Audio amplifiers have long had filters or controls to modify their frequency response. These are most often in the form of variable bass and treble controls (shelving filters), and switches to apply low-cut or high-cut filters for elimination of low frequency “rumble” and high frequency “hiss” respectively.

Graphic equalizers and other equipment developed for improving fidelity have since been used by recording engineers to modify frequency responses for aesthetic reasons. Hence in the field of audio electronics the term “equalization” is now broadly used to describe the application of such filters regardless of intent. This broad definition therefore includes all linear filters at the disposal of a listener or engineer.

A British EQ or British style equalizer is one with similar properties to those on consoles made in the UK by companies such as Amek, Neve and Soundcraft from the 1950s through to the 1970s. Later on, as other manufacturers started to market their products, these British companies began touting their equalizers as being a cut above the rest. Today, many non-British companies such as Behringer and Mackie advertise British EQ on their equipment. A British style EQ seeks to replicate the qualities of the expensive British mixing consoles.

1.1                                             OBJECTIVE OF THE PROJECT

The objective of this work is to construct a circuit or equipment used to achieve audio equalization. These devices strengthen (boost) or weaken (cut) the energy of specific frequency bands or “frequency ranges” of an audio signal.

1.2                                              PURPOSE OF THE PROJECT

The purpose of this work is to build an audio signal equalizer which is most commonly used to correct signals which sound unnatural. For example, if a sound was recorded in a room which accentuates high frequencies, an equalizer can reduce those frequencies to a more normal level. Equalization can also be used for applications such as making sounds more intelligible and reducing feedback.

The most basic type of equalization familiar to most people is the treble/bass control on home audio equipment. The treble control adjusts high frequencies, the bass control adjusts low frequencies. This is adequate for very rudimentary adjustments — it only provides two controls for the entire frequency spectrum, so each control adjusts a fairly wide range of frequencies.

Advanced equalization systems provide a fine level of frequency control. The key is to be able to adjust a narrower range of frequencies without affecting neighbouring frequencies.

1.3                                          APPLICATION OF THE PROJECT

Equalizers are built to control the loss and gain of frequencies within a sound system. This allows a sound system to sound natural and full. It also gives it the ability to maximize volume while eliminating feedback. Many stereos today are built with a graphic equalizer right in the system. But for a high-end stereo system this unit is generally separate and allows fine tuning. Since there are not usually any microphone inputs in a home stereo application, the adjustments usually do not have to take into account the ambient sound in the room, but do help compensate for the “acoustics” in the room.

Equalizers are frequently used in public address systems to sharpen the sound and reduce echoes. Stadiums, sports arenas and other venues will want a good sound system with a good equalizer.

Churches, with their unusually angled rooms and ceilings will especially benefit from having an equalizer in the sound system. As churches often have multiple microphones and speakers, a stereo equalizer is a must.

Schools will want an equalizer to maximize sound output in various venues from auditoriums to gyms. Basketball and volleyball events are enhanced by quality audio equipment allowing for crisp, clear announcements.

Bands and other live traveling shows will perhaps find the equalizer most useful, as it is nearly impossible to construct a good sound system for every venue without adjusting for frequencies that will create feedback.

Most studios have an equalizer, as it is very useful for coordinating the various microphones and sound inputs into the system. It can also reduce and eliminate ambient noises like air-conditioners that may hum in the background.

1.4                                         SIGNIFICANCE OF THE PROJECT

In sound recording and reproduction, equalization is the process commonly used to alter the frequency response of an audio system using linear filters. Most hi-fi equipment uses relatively simple filters to make bass and treble adjustments. Graphic and parametric equalizers have much more flexibility in tailoring the frequency content of an audio signal. An equalizer is the circuit or equipment used to achieve equalization. Since equalizers, “adjust the amplitude of audio signals at particular frequencies,” they are, “in other words, frequency-specific volume knobs.”

1.5                                           LIMITATION OF THE PROJECT

The graphic equalizer circuit adjusts the audio frequency. For some kinds of audio frequency response is not smooth. The frequency offset by the tone controls, may not work well, because the bandwidth is too wide. Requiring the use of e-equalizer circuit with a narrow bandwidth and is divided into frequency bands increased to 5 channels or more can be broken down to specific actions required frequency bands have to be more specific.

1.6                                                 SCOPE OF THE PROJECT

One of the two kinds of equalizers is the graphic equalizer which originates its name from the rough graph of an audio’s altered frequency response which is formed by the glider settings on the front faceplate of an equalizer. The circuit pertains to a classic design by which it can regulate the tone of the acoustic signals into three different ways which includes the low, mid, and high frequencies. This is made possible by utilizing a tone control of the 3 frequencies. A graphic equalizer typically consists of several audio filters or amplifiers with a specific audio range frequency. With the slope range of 18 dB/oct, the amplification or boosting and attenuation or cutting of signals can be done.

This equalizer circuit can adjust the frequency to 3 channel. When entering input signal to signal coupling d through C1 to the position pin 1 of VR1-VR3. If the VR to adjust the position of a signal pin will go to where the second pin of the VR is going through a lot this signal high-frequency filter – a low of each channel.

1.7                                         METHODOLOGY

To achieve the aim and objectives of this work, the following are the steps involved:

1. Study of the previous work on the project so as to improve it efficiency.
2. Draw a block diagram.

• Test for continuity of components and devices,

1. Design and calculation for the device was carried out.
2. Studying of various component used in circuit.
3. Construction of the circuit was carried out.

• Finally, the whole device was cased and final test was carried out.

1.8                                        PROJECT WORK ORGANISATION

The various stages involved in the development of this project have been properly put into five chapters to enhance comprehensive and concise reading. In this project thesis, the project is organized sequentially as follows:

Chapter one of this work is on the introduction to an audio equalizer. In this chapter, the background, significance, objective limitation and problem of an audio equalizer were discussed.

Chapter two is on literature review of an audio equalizer. In this chapter, all the literature pertaining to this work was reviewed.

Chapter three is on design methodology. In this chapter all the method involved during the design and construction were discussed.

Chapter four is on testing analysis. All testing that result accurate functionality was analyzed.

Chapter five is on conclusion, recommendation and references.