Audio and Hi-Fi Handbook

High Performance Audio Power Amplifiers......Page 2
Foreword......Page 5
Contents......Page 6
Preface......Page 12
Acknowledgments......Page 14
System of presentation......Page 16
1.1 What is the problem ?......Page 18
1.2 What is audio ?......Page 19
Appendix 2: Makers’ listings......Page 0
1.5 Some different aims of sound reproduction......Page 20
1.6 About people and their hearing......Page 21
1.8 Why are power amplifiers needed for audio ?......Page 23
1.9 Music fundamentals......Page 25
1.10.1 Tonal qualities......Page 27
1.10.3 General sonic adjectives and nouns......Page 28
1.10.4 Dynamics......Page 29
1.10.5 Space......Page 30
1.11 Nature and range of music (alias programme)......Page 31
1.12 Bass and subsonic content......Page 32
1.13 HF dynamics and ultrasonic content......Page 33
2.1 Common formats for power amps......Page 36
2.2.1 Loudspeaker drive-unit basics......Page 38
2.2.2 Loudspeaker sensitivity vs efficency......Page 42
2.2.3 Loudspeaker enclosure types and efficiencies......Page 43
2.3.1 What loudspeakers look like to the amplifier......Page 49
2.3.2 What speakers are looking for......Page 52
2.3.3 What passive crossovers look like to amplifiers......Page 55
2.4.1 Drive-unit power ratings after EIA/AES......Page 57
2.4.2 Output power capability requirements......Page 58
2.4.3 Loudspeaker vulnerabilities......Page 60
2.4.4 High power, the professional rationale......Page 61
2.5 Current delivery requirements......Page 63
2.5.1 The low impedance route......Page 64
3.1.1 Input sensitivity and gain requirements......Page 66
3.1.2 Input impedance......Page 69
3.2 RF filtration......Page 75
3.3.1 Balancing requirements......Page 76
3.3.2 Introducing Common Mode Rejection......Page 77
3.4 Sub-sonic protection and high-pass filtering......Page 80
3.4.1 Direct Coupling......Page 82
3.5 Damage protection......Page 85
3.6.1 Common gain control (panel attenuator)......Page 88
3.6.2 Remotable gain controls (machine control)......Page 91
3.6.3 Remote control considerations......Page 94
3.6.4 Compression and limiting......Page 95
3.6.7 Soft-Clip......Page 96
3.7 Computer control......Page 97
4.1 Introduction......Page 100
4.1.1 About topologies......Page 101
4.2.1 Out of the vacuum-state......Page 104
4.2.2 Push-pull, Transformer-coupled......Page 105
4.2.3 Sub-topology: the Darlington......Page 106
4.2.5 Sub-topology: diode biasing......Page 108
4.2.6 Complementary push-pull OTL......Page 109
4.1.9 Sub-topology: paralleling......Page 111
4.3 Silicon transistors (Si)......Page 112
4.3.1 The Lin topology......Page 113
4.3.2 Sub-topology: the long-tailed pair (LTP)......Page 115
4.3.3 Sub-topology: the Vbe muliplier (VbeX)......Page 116
4.3.4 Sub-topology: the triple (compound BJT)......Page 117
4.3.6 Sons of Lin......Page 121
4.4 True symmetry: the sequel......Page 122
4.4.1 Later topologies......Page 123
4.4.2 IC power......Page 125
4.4.3 The Op-Amp topologies......Page 127
4.4.4 Power cascades and cascodes......Page 129
4.5 Introducing bridging......Page 130
4.5.1 Bridging the bridge......Page 134
4.6.1 Class A......Page 135
4.6.3 Class A sliding bias and \'Pi-mode\'......Page 140
4.6.6 Sustained plateau biasing......Page 143
4.6.7 Class B and A-B......Page 144
4.6.8 Class A-B, developments and ameliorations......Page 148
4.7 Introducing higher classes......Page 153
4.7.1 Class G......Page 155
4.7.2 Class H......Page 158
4.7.3 G and H, the comparison......Page 160
4.8 Beyond analogue......Page 163
4.8.1 Class D......Page 164
4.9 Class summary......Page 170
4.10 Introducing modes of control......Page 172
4.10.1 Negative feedback modes......Page 173
4.10.2 Other Error Correction Modes......Page 179
4.11 Conclusions......Page 181
5.1.1 Operating with high voltages......Page 186
5.1.2 Operating with high currents......Page 187
5.2.1 Bipolar Junction Transistors (BJT)......Page 188
5.2.2 MOSFETs (enhancement-mode power FETs)......Page 194
5.2.3 Insulated Gate Bipolar Transistors (IGBT)......Page 200
5.3 Recognising large signals......Page 201
5.3.1 The slew limit......Page 202
5.4.1 Power stage, critical layout requirements......Page 208
5.4.2 Critical nodes......Page 209
5.5.1 V-I output capability......Page 215
5.5.2 V-I output limiting (adverse load protection)......Page 217
5.5.3 Mapping V-I capability......Page 227
5.5.4 Audio protection, by fuse......Page 228
5.6.2 Output stability and the output network (OPN)......Page 232
5.6.3 RF protection......Page 234
5.7 DC offset, at output......Page 235
5.7.1 DC (Fault) protection (DCP, DCFP)......Page 236
5.8 The output interface......Page 237
5.8.1 Muting systems......Page 238
5.9 Output stage, cooling requirements......Page 239
5.9.1 Heat exchange......Page 241
5.9.2 Thermal protection......Page 243
5.11 Output transformers......Page 245
6.1 Mains frequency (50/60Hz) supplies......Page 248
6.1.1 50/60Hz EMI considerations......Page 252
6.1.2 Surge handling......Page 254
6.1.3 Actively-adaptive 50/60Hz PSU......Page 255
6.2 Supply amongst channels......Page 257
6.2.2 Operation with 3 Phase AC......Page 259
6.3 Pulse-width power (PWM PSU)......Page 260
6.3.1 HF power supplies (SMPS, HF switchers)......Page 261
6.3.2 Resonant power......Page 264
6.3.4 HF switching summary......Page 267
6.4 Power supply (PSU) efficiency round-up......Page 268
6.4.1 Amplifier efficiency summary......Page 269
6.5 Power supply fusing......Page 270
7.1.1 Types of spec.......Page 274
7.2 Why test things ?......Page 276
7.2.1 Test tools and orientation......Page 277
7.2.2 Realtime test signals......Page 278
7.2.3 The test equipment revolution......Page 281
7.3.1 Mains measurement and conditioning......Page 282
7.3.2 Power amplifier preconditioning......Page 283
7.3.3 The test load......Page 285
7.4 Frequency response (Bandwidth, BW)......Page 289
7.4.1 Gain and balance......Page 291
7.4.2 Output impedance ( Zo)......Page 293
7.4.4 Phase response......Page 295
7.5 Introducing noise......Page 298
7.5.1 Noise spectra......Page 299
7.5.2 Breakthrough and crosstalk (channel separation)......Page 300
7.5.3 Understanding CMR measurements......Page 301
7.5.4 Measuring CMR......Page 302
7.7 Introducing harmonic distortion......Page 303
7.7.1 Harmonics: the musical context......Page 306
7.7.2 Harmonic distortion (THD, %THD+N)......Page 310
7.7.3 Individual harmonic analysis (IHA)......Page 314
7.7.4 Intermodulation (% IMD, Intermod)......Page 315
7.7.5 Dynamic intermodulation (% DIM 30/100)......Page 319
7.7.7 Other distortion tests......Page 320
7.8 Power output......Page 321
7.8.1 Output voltage capability......Page 322
7.8.2 Dynamic output capability......Page 323
7.8.3 Clipping symmetry......Page 324
7.9.1 Rise time (small signal attack)......Page 325
7.9.2 Slew limit (slew rate, large signal attack)......Page 326
7.9.3 Transient response (impulse response)......Page 327
7.9.4 Peak output current capability......Page 329
8.2 Listening......Page 332
8.3 Operable mains range......Page 334
8.3.1 Inrush current......Page 335
8.3.2 Soft start......Page 336
8.3.3 Mains current draw......Page 337
8.4 Signal present indication and metering......Page 338
8.5.1 RF at input......Page 339
8.6 Output DC offset (output offset, Voos)......Page 340
8.6.1 RF at output......Page 341
8.6.4 Adverse loads, low loads and shorting......Page 342
8.7 Thermal protection and monitoring......Page 344
8.8.1 Acoustic noise......Page 345
8.9 EMI and EMC......Page 346
9. Choice, application installation and set- up......Page 348
9.1.1 Choosing the right power amp, domestic......Page 349
9.1.2 Choosing the right power amp, for pro users......Page 352
9.2 Howlers......Page 357
9.3 AC mains voltage......Page 359
9.3.1 Safety earthing......Page 361
9.3.2 Mains cabling......Page 363
9.3.3 Power factor correction......Page 365
9.3.4 Mains fuses and breakers......Page 366
9.3.5 AC mains connectors, amplifier end......Page 367
9.3.7 Mains wiring practice, domestic and studio......Page 369
9.4 Input connections......Page 373
9.4.1 Balanced polarity and shielding......Page 376
9.4.2 Quasi balanced (unbal-to-bal)......Page 377
9.4.3 Input cabling......Page 378
9.5 Output connections......Page 379
9.5.1 Speaker cabling......Page 384
9.5.3 Output polarity......Page 387
9.6.1 Cooling airflow conventions......Page 388
9.6.2 Cooling and air pollution......Page 390
9.7.1 System back-end troubleshooting......Page 391
10.1 Classifying failures......Page 394
10.3 Universal repair procedures......Page 396
10.4.1 Useful tools......Page 406
10.4.2 Test powering tools......Page 407
10.4.3 Audio test tools......Page 409
10.5.1 Testing BJTs (bipolar transistors)......Page 410
10.5.2 Testing MOSFETs......Page 412
10.5.3 Testing diodes, zeners and LEDs......Page 414
10.6 Oscilloscope traces......Page 415
Appendix 1: History......Page 418
A-Z, under principal use......Page 426
A-Z of integrated loudspeaker-amplifier makers......Page 430
Principal output device, by number of makers......Page 431
Appendix 3: Active devices......Page 432
A Bipolar transistors, silicon......Page 433
B Lateral power MOSFETs......Page 437
C Power D-MOSFETs......Page 438
D Termionic valves (electron tubes)......Page 439
Appendix 4: Power amplifier terminology......Page 440
Index......Page 474