Table Of Content

A V S UDIO AND IDEO YSTEMS Principles, Maintenance and Troubleshooting Second Edition About the Author R G Gupta is currently working as Professor (Electronics) in BBD National Institute of Technology and Management, Lucknow, (Affi liated to UP Technical University). He was Director, Police Radio Organization, UP (1983–87). After serving that organization for 26 years (including ten years as Offi cer-in-charge, Technical Institute), he took post-retirement assignments as Senior Consultant in Telecommunication Consultants India Ltd, and later as head of Electronics Engineering Department in M S Institute of Pharmacy and Technology, Delhi. In his 26 years of teaching experience, he taught several courses including advanced radio communication to radio maintenance offi cers of Police Radio, TV Engineering and Satellite Communication to undergraduates at Delhi and Lucknow and Microwave Communication to MTech students of Uttar Pradesh Technical University. Prof. Gupta is a Chartered Engineer (Electronics and Radio Engineering) of the Council of Engineering Institutions, UK and MIERE, MIEEE and FIETE. He took his Master’s degree in Science with specialization in Radio Communication. Post M Sc., he underwent two special courses of one semester each in quality evaluation and maintenance of radars and remote sensing electronic equipment. He was sponsored by the Government of India for advanced training in Budapest in quality control in production and maintenance of VHF/UHF equipment and for study of new techniques used in radio control room in London. He has published 12 papers in various internationally reputed journals. He received the Gowri Memorial Award of IETE for one of these papers and the State Award for another. He has also presented papers in the national seminars held at the University of Roorkee, Engineering University, Jodhpur and IETE. He has authored three books, all published by Tata McGraw Hill, Audio and Video Systems (published in 1995), Electronic Instruments and Systems (published in 2001) and Television Engineering and Video Systems (published in 2006 and the international edition from Singapore was published in 2006). He has been associated with the IETE since 1970; was Chairman of Lucknow Centre for 1978–79 and Jaipur Centre for 1980–81. He has been chairman and member of several national and state-level committees, pertaining to technical standards, telecommunication planning and technical education. In recognition to his work in these fi elds, he has been awarded medal for meritorious service by the President of India, State Award for outstanding work by the Chief Minister of UP and a medal for valuable service in Asian Games 1982 (held in India) by the Games Organizing Committee. A V S UDIO AND IDEO YSTEMS Principles, Maintenance and Troubleshooting Second Edition R G Gupta Professor of Electronics BBD National Institute of Technology and Management UP Technical University Lucknow, Uttar Pradesh Tata McGraw Hill Education Private Limited NEW DELHI McGraw-Hill Offi ces New Delhi New York St Louis San Francisco Auckland Bogotá Caracas Kuala Lumpur Lisbon London Madrid Mexico City Milan Montreal San Juan Santiago Singapore Sydney Tokyo Toronto TataMcGraw Hill Published by Tata McGraw Hill Education Private Limited, 7 West Patel Nagar, New Delhi 110 008 Audio and Video Systems: Principles, Maintenance and Troubleshooting, 2e Copyright © 2010, 1995 by Tata McGraw Hill Education Private Limited No part of this publication may be reproduced or distributed in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise or stored in a database or retrieval system without the prior written permission of the publishers. The program listings (if any) may be entered, stored and executed in a computer system, but they may not be reproduced for publication. This edition can be exported from India only by the publishers, Tata McGraw Hill Education Private Limited. ISBN (13): 978-0-07-069976-2 ISBN (10): 0-07-069976-3 Managing Director: Ajay Shukla Head—Higher Education Publishing: Vibha Mahajan Manager—Sponsoring SEM & Tech Ed: Shalini Jha Assoc. Sponsoring Editor: Suman Sen Development Editor: Manish Choudhary Executive—Editorial Services: Sohini Mukharjee Sr Production Manager: P L Pandita General Manager: Marketing—Higher Education: Michael J Cruz Dy Marketing Manager—SEM & Tech Ed: Biju Ganeshan Asst. Product Manager—SEM & Tech Ed: Amit Banarjee General Manager—Production: Rajender P Ghansela Asst. General Manager—Production: B L Dogra Information contained in this work has been obtained by Tata McGraw Hill, from sources believed to be reliable. However, neither Tata McGraw Hill nor its authors guarantee the accuracy or completeness of any information published herein, and neither Tata McGraw Hill nor its authors shall be responsible for any errors, omissions, or damages arising out of use of this information. This work is published with the understanding that Tata McGraw Hill and its authors are supplying information but are not attempting to render engineering or other professional services. If such services are required, the assistance of an appropriate professional should be sought. Typeset at Text-o-Graphics, B1/56 Arawali Apartment, Sector 34, Noida 201301 and printed at Pashupati Printers Pvt. Ltd., 1/429/16, Gali No. 1, Friends Colony, Industrial Area, G.T. Road, Shahdara, Delhi 110 095 Cover Printer: Rashtriya Printers RALCRRAZRARBD Preface xiii 1. Characteristics of Sound 1 1.1 Nature of Sound 1 1.2 Pressure and Intensity of Sound Waves 4 1.3 Sensitivity of Human Ear for Sound 6 1.4 Frequency of Sound Waves 7 1.5 Overtones and Timbre 8 1.6 Intervals, Octaves and Harmonics 8 1.7 Pitch 9 1.8 Resonance Effect in Sound Systems 9 1.9 Helmholtz Resonator 10 1.10 Refl ection and Diffraction of Sound Waves 10 Summary 11 Review Questions 12 Short-Answer Questions 12 Multiple-Choice Questions 13 Numerical Problems 14 Answers 14 2. Microphones 16 2.1 Introduction 16 2.2 Characteristics of a Microphone 16 2.3 Requisites of a Good Microphone 22 2.4 Moving-Coil Microphone 23 2.5 Ribbon Microphone 26 2.6 Crystal Microphone 30 2.7 Capacitor (or Condenser) Microphone 31 2.8 Electret Microphone 34 2.9 Carbon Microphone 35 2.10 Comparison of Various Types of Microphones 37 2.11 Special Microphones 39 vi Contents Summary 41 Review Questions 43 Short-Answer Questions 44 Multiple-Choice Questions 44 Numerical Problems 45 Answers 46 3. Loudspeakers 48 3.1 Characteristics of Loudspeakers 48 3.2 Moving-Coil Cone-Type Loudspeaker 50 3.3 Electrodynamic Loudspeaker 53 3.4 Horn-type or Indirect Radiating Type Loudspeaker 55 3.5 Comparison between Cone-type and Horn-type Speakers 57 3.6 Loudspeaker column or line source speakers 58 3.7 Baffl es and Enclosures 59 3.8 Multi-way Speaker System (Woofers and Tweeters) 64 3.9 Crossover Networks 64 3.10 Consequence of Mismatch between Amplifi er Output and Loudspeaker Impedance 68 Summary 69 Review Questions 71 Short-Answer Questions 72 Multiple-Choice Questions 72 Numerical Problems 73 Answers 74 4. Gramophone Disc Recording 76 4.1 Principle of Disc Recording 76 4.2 Principle of Disc Reproduction 77 4.3 Block Diagram of a Disc-Recording System 78 4.4 Block Diagram of Disc-Reproduction System 79 4.5 Production of Disc Records on Mass Scale 80 4.6 Types of Grooves 81 4.7 Construction of Cutter Stylus 84 4.8 Playback Needles 85 4.9 Cartridges or Pick-Up Units 86 4.10 Equalisation in Disc Recording/Playback Systems 89 Summary 90 Review Questions 91 Short-Answer Questions 91 Multiple-Choice Questions 92 Numerical Problems 93 Answers 93 Contents vii 5. Magnetic Recording 94 5.1 Principle of Magnetic Recording and Reproduction 94 5.2 Recorded Wavelength, Gap-Width and Tape Speed 95 5.3 Need for Biasing 99 5.4 DC Biasing 99 5.5 AC Biasing 100 5.6 Parts of a Tape Recorder 101 5.7 Tape Transport Mechanism 103 5.8 Advantages and Disadvantages of Tape Recording 105 5.9 Block Diagram of Tape Recorder 106 5.10 Circuit Diagram 107 5.11 ‘Wow’ and ‘Flutter’ Distortions 109 5.12 Rumble 109 5.13 Hissing Noise 109 5.14 Noise-Reduction Techniques 110 5.15 Quality of Sound on Tape 114 Summary 116 Review Questions 117 Short-Answer Questions 118 Multiple-Choice Questions 119 Numerical Problems 120 Answers 120 6. Optical Recording 123 6.1 Types of Optical Recording of Sound 123 6.2 Methods of Optical Recording of Sound on Film 123 6.3 Reproduction of Sound from Films 125 6.4 Modern Method of Recording of Sound for Movie Films 126 6.5 Compact Disc 126 6.6 Optical Recording on Disc 126 6.7 Playback Process 129 6.8 Comparison of Compact Discs and Conventional (Gramophone) Discs 131 Summary 133 Review Questions 134 Short-Answer Questions 134 Multiple-Choice Questions 134 Answers 135 7. Audio Amplifi ers 136 7.1 Types of Audio Amplifi ers 136 7.2 Characteristics of Audio Amplifi ers 138 7.3 Amplifi er Circuits 140 viii Contents 7.4 Negative Feedback in Amplifi ers 144 7.5 Peak Music Power Output (PMPO) 146 7.6 Controls in Audio Amplifi ers 147 7.7 Special Types of Tone Controls 150 Summary 152 Review Questions 153 Short-Answer Questions 154 Multiple-Choice Questions 154 Numerical Problems 155 Answers 156 8. Noise and Distortion 157 8.1 Noise 157 8.2 Methods of Reducing Noise 160 8.3 Distortion 160 8.4 Methods of Reducing Distortion 164 Summary 164 Review Questions 165 Short-Answer Questions 166 Multiple-Choice Questions 166 Answers 167 9. High-Fidelity (or Hi-fi ) 169 9.1 Fidelity 169 9.2 High-Fidelity or Hi-fi 169 9.3 High Signal-to-Noise Ratio 170 9.4 Flat Frequency Response 171 9.5 Low Non-linear Distortion 172 9.6 Large Dynamic Range 172 9.7 Creating Sense of Direction 173 9.8 Creating a Pleasing Environment 173 Summary 174 Review Questions 175 Short-Answer Questions 175 Multiple-Choice Questions 176 Numerical Problems 177 Answers 177 10. Stereophony 178 10.1 Meaning of Stereophony 178 10.2 Stereophony in the Human System of Hearing 178 10.3 Difference between Stereophony and Monophony 178 10.4 Ideal Stereo System 180 Contents ix 10.5 Practical Stereo System 180 10.6 Quadraphonic and Surround-Sound Systems 181 10.7 Stereo Recording on Tape and Reproduction 182 10.8 Tape Cartridge and Cassette Tape 182 10.9 Hi-fi Stereo Reproducing System 184 10.10 Stereo Controls 185 Summary 187 Review Questions 188 Short-Answer Questions 189 Multiple-Choice Questions 189 Answers 190 11. Public Address System 192 11.1 Need and Use 192 11.2 Block Diagram 192 11.3 Requirements of a Public Address System 194 11.4 Typical PA Installation Planning 199 11.5 PA System for a Public Meeting (Large Gathering) 199 11.6 PA System for an Auditorium having Large Capacity 200 11.7 PA System for a Debating Hall 201 11.8 PA System for a Football Stadium 202 11.9 PA System for College Sports 203 Summary 204 Review Questions 205 Short-Answer Questions 206 Multiple-Choice Questions 206 Numerical Problems 207 Answers 207 12. Acoustic Reverberation 209 12.1 Reverberation 209 12.2 Necessity of Reverberation 210 12.3 Typical Reverberation Periods 210 12.4 Factors on which Reverberation Time Depends 210 12.5 Absorption Coeffi cients 211 12.6 Growth and Decay of Sound in an Enclosure 212 12.7 Insulation 215 12.8 Acoustics of Auditoriums 215 Summary 217 Review Questions 218 Short-Answer Questions 218 Multiple-Choice Questions 218 Numerical Problems 219 Answers 220 x Contents 13. Television Fundamentals 221 13.1 Elements of TV Communication System 221 13.2 Scanning 221 13.3 Synchronisation 223 13.4 Aspect Ratio 224 13.5 Picture Elements (Pixels) 224 13.6 Resolution 225 13.7 Bandwidth 225 13.8 Composite Video Signal 227 13.9 Modulation of Video Signals 228 13.10 Modulation of Audio Signals 229 13.11 Monochrome TV Camera Tubes 229 13.12 Colour Cameras 233 13.13 Compatibility 234 13.14 Lumminance Signal 234 13.15 Chrominance Signal 235 13.16 Picture Tubes 235 13.17 Solid State Picture Transducers 238 13.18 TV Broadcasting Systems 238 13.19 Video Monitors 245 13.20 Wide-Dimension High Defi nition TV 246 13.21 MAC Encoder 247 13.22 MAC Receiver and Decoder 249 13.23 Direct-to-Home (DTH) TV 250 13.24 Cable Television (CATV) 250 13.25 Digital TV System 250 Summary 251 Review Questions 252 Short-Answer Questions 252 Multiple-Choice Questions 253 Numerical Problems 254 Answers 254 14. Television Standards 256 14.1 Defi nition 256 14.2 Need of a TV Standard 256 14.3 Reasons of TV Standards Being Different in Different Countries 257 14.4 Different TV Standards 258 14.5 Similarities and Variations in Standards 260 14.6 International Use of TV Standards 261 Summary 262 Review Questions 263