prelims.ian 4/8/98 11:12 AM Page i Audio and Hi-Fi Handbook prelims.ian 4/8/98 11:12 AM Page ii prelims.ian 4/8/98 11:12 AM Page iii Audio and Hi-Fi Handbook Third Edition Editor IAN R. SINCLAIR Newnes OXFORD BOSTON JOHANNESBURG MELBOURNE NEW DELHI SINGAPORE prelims.ian 4/8/98 11:12 AM Page iv Newnes An imprint of Butterworth-Heinemann Linacre House, Jordan Hill, Oxford OX2 8DP 225 Wildwood Avenue, Woburn, MA 01801–2041 A division of Reed Educational and Professional Publishing Ltd A member of the Reed Elsevier plc group First published as Audio Electronics Reference Book by BSP Professional Books 1989 Second edition published by Butterworth-Heinemann 1993 Paperback edition 1995 Third edition 1998 © Reed Educational and Professional Publishing 1998 All rights reserved. No part of this publication may be reproduced in any material form (including photocopying or storing in any medium by electronic means and whether or not transiently or incidentally to some other use of this publication) without the written permission of the copyright holder except in accordance with the provisions of the Copyright, Designs and Patents Act 1988 or under the terms of a licence issued by the Copyright Licensing Agency Ltd, 90 Tottenham Court Road, London, England W1P 9HE. Applications for the copyright holder’s written permission to reproduce any part of this publication should be addressed to the publishers British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library. ISBN 0 7506 3636 X Library of Congress Cataloguing in Publication Data A catalogue record for this book is available from the Library of Congress. Typeset by Jayvee, Trivandrum, India Printed and bound in Great Britain by Clays Ltd, St Ives plc prelims.ian 4/8/98 11:12 AM Page v This book is dedicated to the memory of Fritz Langford-Smith, Mentor and Friend prelims.ian 4/8/98 11:12 AM Page vi prelims.ian 4/8/98 11:12 AM Page vii Contents Preface xi Studio and control room acoustics 33 Chapter 4 Principles of Digital Audio 41 Chapter 1 Sound Waves 1 Allen Mornington-West Dr W. Tempest Introduction 41 Pure tones and complex waveforms 1 Analogue and digital 41 Random noise 2 Elementary logic processes 43 Decibels 2 The significance of bits and bobs 44 Sound in rooms 3 Transmitting digital signals 46 Reverberation 4 The analogue audio waveform 47 Reverberation, intelligibility and music 4 Arithmetic 51 Studio and listening room acoustics 4 Digital filtering 54 The ear and hearing 5 Other binary operations 58 Perception of intensity and frequency 6 Sampling and quantising 58 Pitch perception 7 Transform and masking coders 65 Discrimination and masking 7 Bibliography 65 Binaural hearing 8 The Haas effect 8 Distortion 9 Chapter 5 Compact Disc Technology 67 Electronic noise absorbers 12 Ken Clements References 12 Introduction 67 The compact disc . . . some basic facts 67 The compact disc . . . what information it contains 68 Chapter 2 Microphones 14 Quantisation errors 69 John Borwick Aliasing noise 69 Error correction 71 Introduction 14 How are the errors corrected? 71 Microphone characteristics 14 Interleaving 72 Microphone types 16 Control word 73 The microphone as a voltage generator 18 Eight to fourteen modulation 74 Microphones for stereo 24 Compact disc construction 74 Surround sound 27 The eight to fourteen modulation process 77 References 27 Coupling bits 77 Pit lengths 77 Sync. word 78 Chapter 3 Studio and Control Room Acoustics 28 Optical assembly 80 Peter Mapp Servo circuits 84 The decoder 86 Introduction 28 Digital filtering and digital to analogue conversion 87 Noise control 28 Bibliography 92 prelims.ian 4/8/98 11:12 AM Page viii viii Contents Chapter 6 Digital Audio Recording 93 Dolby SR 152 John Watkinson Dolby S 155 Bibliography 156 Types of media 93 Recording media compared 96 Some digital audio processes outlined 97 Chapter 9 The Vinyl Disc 157 Hard disk recorders 104 Alvin Goldand DonAldous The PCM adaptor 105 An open reel digital recorder 106 Introduction 157 Rotary head digital recorders 107 Background 157 Digital compact cassette 110 Summary of major steps and processes 157 Editing digital audio tape 110 The lathe 158 Bibliography 111 Cutting the acetate 158 In pursuit of quality 160 The influence of digital processing 161 Chapter 7 Tape Recording 112 Disc cutting – problems and solutions 161 John Linsley Hood Disc pressing 162 Disc reproduction 163 The basic system 112 Drive systems 163 The magnetic tape 112 Pick-up arms and cartridges 165 The recording process 113 The cartridge/arm combination 165 Sources of non-uniformity in frequency response 114 Styli 167 Record/replay equalisation 116 Specifications 168 Head design 117 Measurement methods 169 Recording track dimensions 120 Maintaining old recordings 169 HF bias 120 References 170 The tape transport mechanism 123 Transient performance 123 Tape noise 124 Chapter 10 Valve Amplifiers 171 Electronic circuit design 125 Morgan Jones Replay equalisation 127 The bias oscillator 129 Who uses valves and why? 171 The record amplifier 130 Subjectivism and objectivism 172 Recording level indication 131 Fixed pattern noise 172 Tape drive control 131 What is a valve? 172 Professional tape recording equipment 131 Valve models and AC parameters 174 General description 132 Practical circuit examples 176 Multi-track machines 133 Other circuits and sources of information 183 Digital recording systems 134 Recommended further reading 138 Chapter 11 Tuners and Radio Receivers 186 John Linsley Hood Chapter 8 Noise Reduction Systems 139 David Fisher Background 186 Basic requirements for radio reception 186 Introduction 139 The influence of the ionosphere 187 Non-complementary systems 140 Why VHF transmissions? 188 Complementary systems 142 AM or FM? 189 Emphasis 142 FM broadcast standards 190 Companding systems 143 Stereo encoding and decoding 190 The Dolby A system 147 The Zenith-GE ‘pilot tone’ stereophonic system 190 Telecom C4 148 The BBC pulse code modulation (PCM) programme dbx 148 distribution system 192 Dolby B 149 Supplementary broadcast signals 195 Dolby C 150 Alternative transmission methods 195 prelims.ian 4/8/98 11:12 AM Page ix Contents ix Radio receiver design 196 Chapter 15 Loudspeakers 276 Circuit design 212 Stan Kelly New developments 213 Appendix 11.1 BBC transmitted MF and VHF Radiation of sound 276 signal parameters 214 Characteristic impedance 277 Appendix 11.2 The 57 KHz sub-carrier radio Radiation impedance 277 data system (RDS) 214 Radiation from a piston 277 Directivity 277 Sound pressure produced at distance r 277 Chapter 12 Pre-amps and Inputs 215 Electrical analogue 279 John Linsley Hood Diaphragm/suspension assembly 280 Diaphragm size 280 Requirements 215 Diaphragm profile 281 Signal voltage and impedance levels 215 Straight-sided cones 282 Gramophone pick-up inputs 216 Material 283 Input circuitry 217 Soft domes 284 Moving coil PU head amplifier design 219 Suspensions 284 Circuit arrangements 219 Voice coil 285 Input connections 223 Moving coil loudspeaker 285 Input switching 223 Motional impedance 286 References 289 Chapter 13 Voltage Amplifiers and Controls 226 Chapter 16 Loudspeaker Enclosures 290 John Linsley Hood Stan Kelly Preamplifier stages 226 Fundamentals 290 Linearity 226 Infinite baffle 290 Noise levels 230 Reflex cabinets 292 Output voltage characteristics 230 Labyrinth enclosures 295 Voltage amplifier design techniques 231 Professional systems 296 Constant-current sources and ‘current mirrors’ 232 Networks 296 Performance standards 235 Components 298 Audibility of distortion components 237 Ribbon loudspeaker 298 General design considerations 239 Wide range ribbon systems 299 Controls 240 Pressure drive units 300 Electrostatic loudspeakers (ESL) 303 Chapter 14 Power Output Stages 252 Chapter 17 Headphones 310 John Linsley Hood Dave Berriman Valve-operated amplifier designs 252 A brief history 310 Early transistor power amplifier designs 253 Pros and cons of headphone listening 310 Listener fatigue and crossover distortion 253 Headphone types 311 Improved transistor output stage design 255 Basic headphone types 314 Power MOSFET output devices 255 Measuring headphones 316 Output transistor protection 258 The future 317 Power output and power dissipation 259 General power amplifier design considerations 261 Slew-rate limiting and transient intermodulation Chapter 18 Public Address and Sound distortion 262 Reinforcement 319 Advanced amplifier designs 263 Peter Mapp Alternative design approaches 269 Contemporary amplifier design practice 272 Introduction 319 Sound quality and specifications 274 Signal distribution 319 prelims.ian 4/8/98 11:12 AM Page x x Contents Loudspeakers for public address and sound Resistance and electrical effects of current 381 reinforcement 322 Capacitive effects 383 Cone driver units/cabinet loudspeakers 322 Magnetic effects 384 Loudspeaker systems and coverage 325 Characteristic impedance 387 Speech intelligibility 328 Reactive components 388 Signal (time) delay systems 330 Interconnection techniques 390 Equalisers and sound system equalisation 332 Connectors 397 Compressor-limiters and other signal processing equipment 333 Amplifiers and mixers 334 Chapter 22 NICAM Stereo and Satellite Radio Cinema systems and miscellaneous applications 335 Systems 404 References and bibliography 336 Geoff Lewis Chapter 19 In-Car Audio 337 The signal structure of the NICAM-728 system 404 Dave Berriman The NICAM-728 receiver 406 The DQPSK decoder 407 Modern car audio 337 Satellite-delivered digital radio (ASTRA digital FM car reception 337 radio ADR) 407 Power amplifiers 338 Coded orthogonal frequency division multiplex Separate power amps 339 (COFDM) 411 Multi-speaker replay 340 The JPL digital system 413 Ambisonics 340 Reality of digital sound broadcasting 414 Cassette players 341 Compact disc 343 Digital audio tape 344 Chapter 23 Modern Audio and Hi-Fi Servicing 415 Loudspeakers 345 Nick Beer Installation 352 The future for in-car audio 360 Mechanism trends 415 Circuit trends 417 Chapter 20 Sound Synthesis 362 Tuners 418 Mark Jenkins Power supplies 418 System control 419 Electronic sound sources 362 Microprocessors 419 Synthesizers, simple and complex 362 Amplifiers 419 Radiophonics and sound workshops 363 Discrete output stage failures 422 Problems of working with totally artificial Digital signal processing 423 waveforms 366 Mini-disc 423 Computers and synthesizers (MIDI and MSX) 368 Test modes 424 Mode messages 373 Surface mounted and VLSI devices 424 Real time 376 Obsolete formats 425 References 377 Software problems 425 Good servicing practice 426 Chapter 21 Interconnections 378 Test equipment 426 Allen Mornington-West Conclusion 426 Target and scope of the chapter 378 Index 427 Basic physical background 378