Index

PREAMPLIFIERS & MIXERS

A

Absolute phase 34, 54
Active rectifiers 122
Active volume control 14, 25, 26, 52, 76
Analog gates 139, 144
control voltage feedthrough 154
in current mode 151
distortion of 154
paralleling 151
series-shunt 153
series switching 146
voltage mode 146
Attack time 123–5
Attenuator 133
Auxiliary sends 134

B

Balance control 23, 32, 69
Balanced line inputs 104
Balanced line outputs 99
Balanced mix bus 137
Bass frequency control 73
Baxandall, Peter 7, 26, 33, 128
Bootstrapping: 
collector loads 22
Buffer stage 31, 34, 52
Bus residual 137

C

Channel muting 139
Clipping detection 8
Close-tolerance capacitors 30, 60
Common-impedance coupling 95
Common-mode rejection (CMRR) 96, 104, 133
Compressor 117–26
Crosstalk 35, 39, 67, 83, 112, 137

D

DC blocking 42, 82, 157
Decay time 123–5
Decoupling 34
Differential amplifier 105
Differential pair input 42
Distortion 146, 158

E

Effect returns 135
Electrostatic coupling 93
End-stop resistors 73
EQ 134

F

FETs 118
distortion cancellation 120
switching 139
Foldback 134, 135
Frequency response 3

G

Galvanic isolation 102, 143
Ground-cancelling outputs 98
Ground currents 95
Ground loops 11, 91
Grounding 95
Group module 128

H

HF stability 159, 163

I

Impedance-balanced line outputs 97
Input impedances 69, 103, 106, 108, 122
Input selector switch 52, 67
Instrumentation amplifiers 111

J

JFETs: 
cascaded switches 160
changeover 159
control voltage feedthrough 169
current mode 161
series switching 155
shunt switching 160
Johnson noise 54, 55, 61, 69, 110, 151

L

Ladder attenuator 46
LED biasing 1
Limiter 117–26
Line inputs 102
Line outputs 97–102
Linear controls 33, 73, 77, 135
Linearity 40, 150
Lipshitz, Stanley 30
Low-impedance design 31

M

Magnetic coupling 94
Microphone preamplifiers 110, 128
Mix bus 137
Mixdown 141
Mixing desks 107, 127–41
Moving-coil cartridges 37, 54, 88
output voltages 38, 54, 88
Moving-magnet cartridges 38
Multiple input devices 40
Multitrack recording 140
Mute blocks 162
Muting relay 7, 9, 80

N

Negative feedback 14, 43
Negative-impedance converters 136
Noise gating 2, 9
Noise, Johnson 54, 55, 61, 110
Noise performance 25, 31, 39, 47, 61–3, 70, 73, 75, 84, 140
Normalization amplifier 6
Nyquist stability criterion 17

O

Offness 143
Opamps 24, 34, 50, 74, 107, 150
compensation 34, 65
Overload margin 2, 4, 14, 55, 86–9

P

Panpots 135
Passive equalisation 57
Phantom power 133
Phase-shift 76
Phase-splitter 122
Physical layout 10, 22, 48
Post-fade sends 135
Power supply 10, 14, 22, 34, 82
Preamplifier: 
architecture 25, 55
distortion 3, 14, 19
output levels 52
Prefade-listen (PFL) 128
Prefade sends 135
Push–Pull Class-A operation 13

Q

Quasi-floating outputs 100

R

Recording 140
Relay control 80
Relays 143
RIAA equalization 2, 14, 19, 30, 53, 54, 57–61, 88
IEC amendment 30, 88
Routing matrix 141

S

Screened cables 92
Series feedback in phono stage 2
Shunt feedback in phono stage 2
Shunt muting circuits 150
Signal-to-noise ratio 14
Soft changeover 168–9
Solid-state switching 128, 139
SPICE simulation 74
Subsonic filter 14, 31, 62, 140
Summing amplifiers 137
Superbal amplifier 108
Switched-gain balanced amplifier 107
Switch-on transients 161
Symmetry 139

T

Tape monitoring 69, 141
Tape outputs 6, 50, 69
Tone cancel 75
Tone controls 7, 22, 26, 32, 50, 70–2, 128, 134
Transformer inputs 104, 133
Transformer outputs 102
Treble frequency control 72

U

Unbalanced line inputs 103
Unbalanced line outputs 97
Unity-gain buffers 52

V

Variable-gain balanced amplifier 109
Vernier balance control 69
Virtual-earth 137
Virtual mixing 141
Voltage-controlled attenuator (VCA) 118
Volume control 3, 52, 77
gain law 33
imbalance 33
VU meters 8

Z

Zero-crossing detection 80, 139, 162

POWER AMPLIFIERS

A

AC coupling 137
Amplifier classes 404

B

Balance of input stage 207
Balanced VAS 226
Band-gap references 352
Batman curve 396
Bipolar beta droop 252, 369, 371
Blameless amplifiers 266, 319
Blomley amplifier 406
Bootstrapping: 
collector loads 215, 222, 393
input 344, 378

C

Capacitor distortion 171
Cascode VAS 174, 224
Class-A 232, 301, 405
quiescent current control 349
Class-AB 233, 406
Class-B 233, 406
Class-C 406
Class-D 406
Class-G 414, 440
Class-S 408
Commutating amplifier 412
Compensation 279
dominant pole 195, 280
lag 281
two pole 284, 290
Complementary feedback pair (CFP) 247, 358
Conjugate curves 182, 235, 254
Constant-gm degeneration 212, 215
Crossover distortion 191, 192, 232–49, 254, 324
Current-mirrors 175, 208

D

Darlingtons 245
DC offset detection 171, 428
DC offset voltage 175, 202, 204, 208, 347
Decoupling 272–4
Degeneration 206
Differential input stage 202
Distortion 191
Dominant pole 189

E

Edwin amplifier 410
Emitter degeneration 206
Emitter-followers 175

F

Feedback factor 359, 383, 393, 394
Feedforward diodes 366
FET output stage 172, 182, 394

G

Gain measurement (open-loop) 196
Gm doubling 233

H

Harmonics 188, 192
Hybrid BJT/FET output stages 176

I

Inclusive Miller compensation 282
Input currents 310
Input impedance of output stage 176, 258
Input Stage cascoding 214
Input stages: 
bipolar 199
cascode 315, 394
Cascomp 212, 213
CFP input 212, 214
cross-quad 212, 213
current-mirror loading 175, 208
differential 202
FET 314
offset voltage 202
singleton 204
Instability, high frequency 279–84

J

Johnson noise 311

L

Latch-up 359
Lag compensation 281
Large-signal non-linearity 251–4, 328, 366
Linearity 186, 196, 201
Load-invariant amplifier 363
Loudspeaker currents 400

M

Mains-fail detection 426
Miller integrator 175, 194
Model amplifiers 198
Muting relays 421

N

Negative feedback 171, 378
Nested feedback 282
Noise, Johnson 311, 343
Noise performance 342
Nyquist stability criterion 197, 221, 359

O

Opamps 154
Open-loop bandwidth 227–8
Open-loop gain: 
calculation 196
measurement 196
Oscillation 176
Output capacitors 204
Output stages: 
complementary feedback pair (CFP) 247
emitter follower 245
FET 248
quasi-complementary 247
triples 248

P

Peak power dissipation 445–6
Peak-to-mean ratio 448
Phase margin 282
Phase-splitter 395
Pole 189, 280
Pole splitting 281
Power amplifiers: 
blameless 266, 287
Blomley 406
Class-A 217
Power dissipation 434
Power-partition diagrams 438
Power supplies 171
Power supply rejection 194, 274, 394
Push–pull operation 295

Q

Quarter-squares principle 380
Quasi-complementary output stages: 
bipolar 247
FET 176
Quiescent current: 
control in Class-A 301
control in Class-B 265, 288

R

Reactive loads 442
Relays 171, 421–33
Residual 319
Ripple rejection 311

S

Singleton input stage 204
Slew-rate 171, 175, 215, 357, 429
Spectrum analysis 233
SPICE simulation 186, 188, 369, 401, 435
Stability of power amp 279–84
Switchoff distortion 256

T

Thermal compensation 375
Thermal design 354
Thermal distortion 194
Total Harmonic Distortion 319
Transconductance 183, 201–203, 206, 211, 217, 219, 222
Transient response 27
Transistor beta 348
Transresistance 189
Trimodal amplifier 334
Turn-on transients 424
Two pole compensation 284
Two-stage amplifiers 391

U

Underbiasing 233

V

VAS buffering 176, 225, 237
Vbe multiplier 349
Voice-coil inductance 401
Voltage amplifier stage (VAS) 173, 217

W

Warm-up time 353

Z

Zener clamping (of relays) 427
Zero-crossing detection 426
Zobel network 289
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