Design And Construction Of A Two Input Mixer Amplifier

ABSTRACT

An audio mixer amplifier is an electronic device for combining, and modifying audio signals. The modified audio signals are summed to produce some combined amplified output signals.

Mixer amplifiers are most often used by recording studios but are also typically used in live situations by live sound engineers. There are two types of mixers, digital and analog, and both are commonly used by the same recording studio to achieve different results. In this work, an analog audio mixer using common electronics components, such as resistors, capacitors, potentiometers and operational amplifiers (Op-Amps).

The aim of this work is to build a 2-channel mixer which can accept two different audio signals at the same time and mix their different tracks by changing their volume levels.

TABLE OF CONTENTS

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWLEDGEMENT

ABSTRACT

CHAPTER ONE

1.0 INTRODUCTION

1.1 BACKGROUND OF THE PROJECT

1.2 PROBLEM STATEMENT

1.3 AIM AND OBJECTIVES OF THE PROJECT

1.4 PURPOSE OF THE PROJECT

1.5 APPLICATION OF THE PROJECT

1.6 SIGNIFICANCE OF THE PROJECT

1.7 SCOPE OF THE PROJECT

1.8 DEFINITION OF TERMS

CHAPTER TWO

2.0 LITERATURE REVIEW

2.1      OVERVIEW OF THE STUDY

2.2      HISTORICAL BACKGROUND OF AN AMPLIFIER

2.3      FURTHER DEVELOPMENTS OF AMPLIFIER

2.4      APPLICATIONS OF AMPLFIER

2.5          REVIEW OF AUDIO MIXING

2.6      REVIEW OF MIXERS

2.7          TYPES OF MIXERS

2.8      FEATURES OF MIXERS

CHAPTER THREE

3.0 DESIGN METHODOLOGY

3.1      SYSTEM BLOCK DIAGRAM

3.2  UNIT CIRCUIT DIAGRAMS

3.2.1       Two input mixing Preamp Circuit diagram

3.2.2       Mixing and Preamp Parts

3.2.3       Mixing and Preamp circuit description

3.2.4       Power Amplifier Circuit diagram

3.2.5       Power Amplifier Parts

3.2.6       Power Amplifier Circuit description

3.2.7       Power Supply Circuit diagram

3.2.8       Power Supply Parts

CHAPTER FOUR

RESULT ANALYSIS

4.0   CONSTRUCTION PROCEDURE AND TESTING

4.1   CASING AND PACKAGING

4.2  ASSEMBLING OF SECTIONS

4.3 TESTING OF SYSTEM OPERATION

CHAPTER FIVE

5.1 CONCLUSION

5.2 RECOMMENDATION

REFERENCES

CHAPTER ONE

1.0                                                        INTRODUCTION

1.1                                           BACKGROUND OF THE STUDY

Audio mixer is an electronic device for combining, routing, and changing the level, timbre and/or dynamics of audio signals. A mixer can mix analog or digital signals, depending on the type of mixer. The modified signals (voltages or digital samples) are summed to produce the combined output signals [1].

Mixers are used in many applications, including recording studios, public address systems, sound reinforcement systems, broadcasting, television, and film post-production [2]. An example of a simple application would be to enable the signals that originated from two separate microphones to be heard through one set of speakers simultaneously. When used for live performances, the signal produced by the mixer will usually be sent directly to an amplifier. An audio amplifier amplifier that amplifies low-power audio signals from the mixer (signals composed primarily of frequencies between 20 – 20 000 Hz, the human range of hearing) to a level suitable for driving loudspeakers. It is the final electronic stage in a typical audio playback chain [3].

In other words, an audio amplifier amplifies the power of the input signal which is why these types of amplifier circuits are used in audio amplifier output stages to drive loudspeakers.

1.2                                          STATEMENT OF THE PROBLEM

In music industry, selection of different audio input to produce one amplified output is always difficult and it involves application of more electronics circuits. Mixers amplifiers allow for precise tuning of microphone inputs and speaker outputs. The result is clearer sound, and more volume from the sound system.

1.3                                          RESEARCH AIM AND OBJECTIVES

The aim of this work is to build an audio amplifier which have and can accept two low different audio inputs to give out one amplified output. And the level of each audio input is controlled with potentiometer. The objectives of the study are:

1. To build the system prototype
2. To understand the operation of an audio amplifier

• To read and analyze the circuit diagram of a two input audio amplifier

1.4                                          PURPOSE OF THE PROJECT

The purpose of this work is to amplify low-power electronic audio signals such as the signal from microphone or electric guitar pickup to a level that is high enough for driving loudspeakers. Amplifier takes weak signal and make it strong to drive a speaker.

1.5                                          APPLICATION OF THE PROJECT

Important applications include public address systems, theatrical and concert sound reinforcement systems, and domestic systems such as a stereo or home-theatre system.

Public address systems use a mixing console to set microphones to an appropriate level, and can add in recorded sounds into the mix. A major requirement is to minimize audio feedback [4].

Most bands use a mixing console to combine musical instruments and vocals.

Radio broadcasts use a mixing desk to select audio from different sources, such as CD players, telephones, remote feeds, or prerecorded advertisements. These consoles, often referred to as “air-boards” are apt to have many fewer controls than mixers designed for live or studio production mixing, dropping pan/balance, EQ, and multi-bus monitoring/aux feed knobs in favor of cue and output bus selectors, since, in a radio studio, nearly all sources are either prerecorded or pre-adjusted [6]. Noise music musicians may create feedback loops within mixers, creating an instrument known as a no-input mixer. The tones generated from a no-input mixer are created by connecting an output of the mixer into an input channel and manipulating the pitch with the mixer’s dials [8]. Other places audio mixer have greater application include: including recording studios, public address systems, sound reinforcement systems, nightclubs, broadcasting, television, and film post-production. A typical, simple application combines signals from microphones on stage into an amplifier that drives one set of loudspeakers for the audience and also in a DJ mixer [6].

1.6                                          SIGNIFICANCE OF THE PROJECT

Today there are many categories of mixer amplifiers used for multifarious purposes. In simple terms an amplifier picks up a weak signal and converts it into a strong one. It is widely used in several devices to boost electrical signals. Radios, televisions and telephones are a few examples to point out in this regard. There are innumerable other applications of amplifiers and it is not easy to enumerate all of them. Some of the common types of mixer amplifiers are used in electronic gadgets and audio systems. These are also used in musical instruments and guitars.

The role of a music producer is not necessarily a technical one, with the physical aspects of recording being assumed by the audio engineer, and so producers often leave the similarly technical mixing process to a specialist audio mixer. Even producers with a technical background may prefer that a mixer comes in to take care of the final stage of the production process.

Audio mixing is done in studios as part of creating an album or single. The mixing stage often follows a multitrack recording. The process is generally carried out by a mixing engineer, though sometimes it is the musical producer, or even the artist, who mixes the recorded material. After mixing, a mastering engineer prepares the final product for reproduction on a CD, for radio, or otherwise.

1.7                  SCOPE OF THE STUDY

The scope of this work covers taking two audio signals, merges them together and provides one output signals which is achieved by the arrangement of mixing, pre-amplifying and amplifier circuit.

1.8                                                      DEFINITION OF TERMS

Acoustics – the science or study of sound.

Alternating (AC) Current – currents that have a harmonic time dependence.

Ampere (A) – the unit of measurement for electrical current in coulombs per second.

Amplifier – an electrical circuit designed to increase the current or voltage of an applied signal.

Audio frequency – the acoustic spectrum of human hearing, generally regarded to be between 20 Hz and 20 kHz.

Capacitor – a charge storage device made up of two metallic plates separated by a dielectric, with equal but opposite charges. The AC impedance of a Capacitor is (1 / jWL) and acts as an open circuit in DC applications.

Circuit – a complete path that allows electrical current from one terminal of a voltage source to the other terminal.

Decibel (dB) – (1) a logarithmic scale used to denote a change in the relative strength of an electric signal or acoustic wave. It is a standard unit for expressing the ratio between power and power level. Using the logarithmic relationship for power PdB = 10*log[Pout/Pin] , a doubling of electrical power only yields an increase of +3 dB. Increasing the power tenfold will yield an increase of +10 dB and is a doubling of perceived loudness. The decibel is not an absolute measurement, but indicates the relationship or ratio between two signal levels. (2) SPL (sound pressure level) can be measured in dB. 0 dB represents the threashold of normal human hearing, 130 dB represents the threashold for pain, 140 dB causes irreparible hearing damage, and 150 dB can cause instant deafness, anything greater than about 192 dB can kill you.

Direct Current (DC) – current in only one direction.

Driver – a loudspeaker unit, consisting of the electromagnetic components of a speaker, typically a magnet and voice coil.

Hertz (Hz) – a measurement of the frequency of sound vibration. One hertz is equal to one cycle per second. The hertz is named for H.R. Hertz, a German physicist.

Input – connection from signal source.

Output – the sound level produced by a loudspeaker.

CHAPTER FIVE

5.1                                                           CONCLUSION

The target of this work was the design of a high quality microphone mixer. The mixer is formed assembling some main modules that can be varied in number and/or disposition to suit everyone needs.

There is always much room for improvements. If you have any new ideas, some additions, corrections or complaints feel free to provide feedback.

5.2                                                    RECOMMENDATION

This project is designed to be used in our homes, engineering laboratory, offices and music industries where there is need for three different microphones in one amplifier. And if fail should be used and maintain by a qualified personnel.