Audio Amplifier Performance

926 Pages·2008·6.2 MB·English

Audio Engineering
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Audio Engineering
Douglas Self
Richard Brice
Ben Duncan
John Linsley Hood
Ian Sinclair
Andrew Singmin
Don Davis
Eugene Patronis
John Watkinson
AMSTERDAM • BOSTON • HEIDELBERG • LONDON • NEW YORK • OXFORD
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Library of Congress Cataloging-in-Publication Data
Audio engineering : know it all / by Ian Sinclair … [et al.].
p. cm.
Includes bibliographical references and index.
ISBN 978-1-85617-526-5 (alk. paper)
1. Sound—Recording and reproducing—Handbooks, manuals, etc. 2. Sound—Recording
and reproducing—Digital techniques—Handbooks, manuals, etc. I. Sinclair, Ian Robertson.
TK7881.4.A9235 2008
621.389(cid:3)3—dc22
2008033305
British Library Cataloguing-in-Publication Data
A catalogue record for this book is available from the British Library.
ISBN: 978-1-85617-526-5
For information on all Newnes publications
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Printed in The United States of America
Contents
About the Authors .............................................................................................................xv
I: Fundamentals of Sound ..................................................................................................1
Chapter 1: Audio Principles ...............................................................................................3
1.1 The Physics of Sound ................................................................................................3
1.2 Wavelength ................................................................................................................4
1.3 Periodic and Aperiodic Signals .................................................................................5
1.4 Sound and the Ear ......................................................................................................6
1.5 The Cochlea ...............................................................................................................9
1.6 Mental Processes .....................................................................................................11
1.7 Level and Loudness .................................................................................................14
1.8 Frequency Discrimination........................................................................................16
1.9 Frequency Response and Linearity ..........................................................................20
1.10 The Sine Wave .........................................................................................................22
1.11 Root Mean Square Measurements ...........................................................................25
1.12 The Decibel ..............................................................................................................26
1.13 Audio Level Metering ..............................................................................................30
References ................................................................................................................32
Chapter 2: Measurement ..................................................................................................33
2.1 Concepts Underlying the Decibel and its Use in Sound Systems ...........................33
2.2 Measuring Electrical Power .....................................................................................38
2.3 Expressing Power as an Audio Level ......................................................................39
2.4 Conventional Practice ..............................................................................................40
2.5 The Decibel in Acoustics—L ,L , and L ..............................................................42
P W I
2.6 Acoustic Intensity Level (L), Acoustic Power Level (L ),
I W
and Acoustic Pressure Level (L ) ............................................................................44
P
2.7 Inverse Square Law ..................................................................................................46
2.8 Directivity Factor .....................................................................................................47
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vi Contents
2.9 Ohm’s Law ..............................................................................................................47
2.10 A Decibel is a Decibel is a Decibel .........................................................................48
2.11 Older References .....................................................................................................48
2.12 The Equivalent Level (L ) in Noise Measurements ..............................................51
EQ
2.13 Combining Decibels ................................................................................................54
2.14 Combining Voltage ..................................................................................................58
2.15 Using the Log Charts ...............................................................................................58
2.16 Finding the Logarithm of a Number to Any Base ...................................................60
2.17 Semitone Intervals ...................................................................................................61
2.18 System Gain Changes ..............................................................................................62
2.19 The VU and the Volume Indicator Instrument ........................................................62
2.20 Calculating the Number of Decades in a Frequency Span ......................................68
2.21 Defl ection of the Eardrum at Various Sound Levels ...............................................69
2.22 The Phon ..................................................................................................................70
2.23 The Tempered Scale ................................................................................................73
2.24 Measuring Distortion ...............................................................................................73
2.25 The Acoustical Meaning of Harmonic Distortion ...................................................74
2.26 Playback Systems in Studios ...................................................................................76
2.27 Decibels and Percentages ........................................................................................77
2.28 Summary .................................................................................................................79
Further Reading .......................................................................................................79
Chapter 3: Acoustic Environment ....................................................................................81
3.1 The Acoustic Environment ......................................................................................81
3.2 Inverse Square Law .................................................................................................82
3.3 Atmospheric Absorption .........................................................................................84
3.4 Velocity of Sound ....................................................................................................85
3.5 Temperature-Dependent Velocity ............................................................................88
3.6 The Effect of Altitude on the Velocity of Sound in Air ..........................................88
3.7 Typical Wavelengths ................................................................................................89
3.8 Doppler Effect .........................................................................................................90
3.9 Refl ection and Refraction ........................................................................................91
3.10 Effect of a Space Heater on Flutter Echo ................................................................92
3.11 Absorption ...............................................................................................................94
3.12 Classifying Sound Fields .........................................................................................97
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Contents vii
3.13 The Acoustic Environment Indoors ......................................................................102
3.14 Conclusion ............................................................................................................112
Further Reading.....................................................................................................113
II: Audio Electronics .......................................................................................................115
Chapter 4: Components ..................................................................................................117
4.1 Building Block Components .................................................................................117
Chapter 5: Power Supply Design ....................................................................................139
5.1 High Power Systems .............................................................................................139
5.2 Solid-State Rectifi ers.............................................................................................143
5.3 Music Power..........................................................................................................144
5.4 Infl uence of Signal Type on Power Supply Design ..............................................144
5.5 High Current Power Supply Systems ....................................................................146
5.6 Half-Wave and Full-Wave Rectifi cation ...............................................................147
5.7 Direct Current Supply Line Ripple Rejection .......................................................147
5.8 Voltage Regulator Systems ...................................................................................148
5.9 Series Regulator Layouts ......................................................................................150
5.10 Overcurrent Protection ..........................................................................................152
5.11 Integrated Circuit (Three Terminals) Voltage Regulator ICs ................................153
5.12 Typical Contemporary Commercial Practice ........................................................157
5.13 Battery Supplies ....................................................................................................159
5.14 Switch-Mode Power Supplies ...............................................................................159
Reference ..............................................................................................................159
III: Preamplifi ers and Amplifi ers ...................................................................................161
Chapter 6: Introduction to Audio Amplifi cation............................................................163
Chapter 7: Preamplifi ers and Input Signals ..................................................................167
7.1 Requirements ........................................................................................................167
7.2 Signal Voltage and Impedance Levels ..................................................................167
7.3 Gramophone Pick-Up Inputs ................................................................................169
7.4 Input Circuitry .......................................................................................................171
7.5 Moving Coil Pick-up Head Amplifi er Design ......................................................175
7.6 Circuit Arrangements ............................................................................................176
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viii Contents
7.7 Input Connections .................................................................................................183
7.8 Input Switching .....................................................................................................184
7.9 Preamplifi er Stages ...............................................................................................186
7.10 Linearity ................................................................................................................188
7.11 Noise Levels ..........................................................................................................197
7.12 Output Voltage Characteristics ..............................................................................198
7.13 Voltage Amplifi er Design ......................................................................................200
7.14 Constant-Current Sources and “Current Mirrors” ................................................202
7.15 Performance Standards .........................................................................................209
7.16 Audibility of Distortion .........................................................................................212
7.17 General Design Considerations .............................................................................218
7.18 Controls .................................................................................................................219
References .............................................................................................................239
Chapter 8: Interfacing and Processing ..........................................................................241
8.1 The Input ...............................................................................................................241
8.2 Radio Frequency Filtration ...................................................................................252
8.3 Balanced Input ......................................................................................................253
8.4 Subsonic Protection and High-Pass Filtering ........................................................257
8.5 Damage Protection ................................................................................................263
8.6 What Are Process Functions? ...............................................................................267
8.7 Computer Control .................................................................................................278
References .............................................................................................................280
Chapter 9: Audio Amplifi ers ...........................................................................................283
9.1 Junction Transistors ..............................................................................................283
9.2 Control of Operating Bias .....................................................................................286
9.3 Stage Gain .............................................................................................................288
9.4 Basic Junction Transistor Circuit Confi gurations .................................................289
9.5 Emitter–Follower Systems ....................................................................................291
9.6 Thermal Dissipation Limits ..................................................................................294
9.7 Junction Field Effect Transistors (JFETs) ............................................................295
9.8 Insulated Gate FETs (MOSFETs) .........................................................................299
9.9 Power BJTs vs Power MOSFETs as Amplifi er Output Devices ..........................303
9.10 U and D MOSFETs ...............................................................................................305
9.11 Useful Circuit Components ...................................................................................307
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Contents ix
9.12 Circuit Oddments ..................................................................................................309
9.13 Slew Rate Limiting ...............................................................................................311
References .............................................................................................................312
Chapter 10: Audio Amplifi er Performance ....................................................................313
10.1 A Brief History of Amplifi ers ...............................................................................313
10.2 Amplifi er Architectures.........................................................................................314
10.3 The Three-Stage Architecture ...............................................................................314
10.4 Power Amplifi er Classes .......................................................................................317
10.5 AC- and DC-Coupled Amplifi ers ..........................................................................325
10.6 Negative Feedback in Power Amplifi ers ...............................................................330
References .............................................................................................................334
Chapter 11: Valve (Tube-Based) Amplifi ers ...................................................................337
11.1 Valves or Vacuum Tubes .......................................................................................337
11.2 Solid-State Devices ...............................................................................................349
11.3 Valve Audio Amplifi er Layouts ............................................................................350
11.4 Single-Ended Versus Push–Pull Operation ...........................................................352
11.5 Phase Splitters .......................................................................................................355
11.6 Output Stages ........................................................................................................358
11.7 Output (Load-Matching) Transformer ..................................................................360
11.8 Effect of Output Load Impedance .........................................................................364
11.9 Available Output Power ........................................................................................365
References .............................................................................................................366
Chapter 12: Negative Feedback ......................................................................................367
12.1 Amplifi er Stability and Negative Feedback ..........................................................367
12.2 Maximizing Negative Feedback ............................................................................377
12.3 Maximizing Linearity Before Feedback ...............................................................378
Further Reading.....................................................................................................379
Chapter 13: Noise and Grounding .................................................................................381
13.1 Audio Amplifi er Printed Circuit Board Design ....................................................381
13.2 Amplifi er Grounding .............................................................................................390
13.3 Ground Loops: How They Work and How to Deal with Them ............................393
13.4 Class I and Class II................................................................................................400
13.5 Mechanical Layout and Design Considerations....................................................401
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