Valve Amplifiers

✍ Scribed by Jones, Morgan

• Publisher: Newnes
• Year: 2011
• Tongue: English
• Leaves: 701
• Edition: 4
• Category: Library

✦ Synopsis

Reviews of previous editions:

"Jam-packed with theory, circuit analysis, and DIY basics, it will walk you through all stages of design so that you can create your own wonders. Jones is an ex-BBC engineer with a cool writing style and you ll find it a no-pain education." Hi-Fi News and Record Review

"Valve Amplifiers is an extremely well written book, containing a wealth of information that all audio designers and builders will find useful." Glass Audio

Valve Amplifiers is a market leader for one simple reason: in this specialist area it is recognized as the most complete guide to valve and vacuum tube amplifier design, modification, analysis, construction and maintenance. It is truly the all you need to know guide, and enables audio and circuit designers to succeed with their valve amplifier designs and projects.

This book enables readers to understand, create, reconfigure and personalize high-end, audiophile quality amplifiers. Following a step-by-step approach to design, with little maths and lots of know-how, it starts with a brief review of electronic fundamentals relevant to valve amplifiers, simple stages, compound stages, linking stages together, and finally, complete designs.

The new material included in this Fourth Edition ensures this book will stay at the top of any audio designer s or enthusiast s reference list.

What s new within the chapters:

Chapter 1: Charge amplifiers

Chapter 2: Additional circuits, semiconductor constant current sources expanded

Chapter 3: Entire new section on noise

Chapter 4: Lots of new measurements to explode or explain audio folklore

Chapter 5: Astonishingly quiet, but cheap and simple HT supply

Chapter 6: New power amplifier

Chapter 7: New hybrid balanced RIAA stage, attenuator law faking

VA3's focus was on distortion, but in VA4, focus is pushed towards background noise reduction. If that wasn t enough, there s more explanation, more measurements, more references, and plenty of new one-liners, any one of which might save hours of trouble.
The practical guide to analysis, modification, design, construction and maintenance of valve amplifiers
The fully up-to-date approach to valve electronics
* Essential reading for audio designers and music and electronics enthusiasts alike

✦ Table of Contents

Front Cover......Page 1
Valve Amplifiers......Page 4
Copyright Page......Page 5
Contents......Page 6
Preface......Page 10
Dedication......Page 12
Acknowledgements......Page 14
Mathematical Symbols......Page 16
Electrons and Definitions......Page 17
Batteries and Lamps......Page 19
Ohm’s Law......Page 20
Power......Page 21
Kirchhoff’s Laws......Page 22
Resistors in Series and Parallel......Page 24
Equivalent Circuits......Page 29
The Thévenin Equivalent Circuit......Page 30
The Norton Equivalent Circuit......Page 33
Units and Multipliers......Page 34
The Decibel......Page 35
The Sine Wave......Page 36
The Transformer......Page 39
Capacitors, Inductors and Reactance......Page 40
Filters......Page 42
Time Constants......Page 45
Resonance......Page 46
RMS and Power......Page 48
The Square Wave......Page 49
Square Waves and Transients......Page 50
Random Noise......Page 55
Conventional Current Flow and Electron Flow......Page 56
Silicon Diodes......Page 57
Voltage References......Page 58
Bipolar Junction Transistors (BJTs)......Page 60
The Common Emitter Amplifier......Page 62
Input and Output Resistances......Page 64
The Emitter Follower......Page 66
General Observations on BJTs......Page 67
The Feedback Equation......Page 68
Practical Limitations of the Feedback Equation......Page 69
Feedback Terminology and Input and Output Impedances......Page 70
The Operational Amplifier......Page 71
The Inverter and Virtual Earth Adder......Page 72
The Non-Inverting Amplifier and Voltage Follower......Page 73
The Charge Amplifier......Page 75
DC Offsets......Page 77
Recommended Further Reading......Page 78
The Common Cathode Triode Amplifier......Page 80
Limitations on Choice of the Operating Point......Page 83
Conditions at the Operating Point......Page 85
Dynamic, or AC, Parameters......Page 88
Cathode Bias......Page 91
The Effect on AC Conditions of an Unbypassed Cathode Bias Resistor......Page 93
The Cathode Decoupling Capacitor......Page 94
Choice of Value of Grid-Leak Resistor......Page 96
Miller Capacitance......Page 98
Guided-Grid, or Beam, Triodes......Page 100
The Tetrode......Page 101
The Beam Tetrode and the Pentode......Page 102
The Significance of the Pentode Curves......Page 104
Using the EF86 Small-Signal Pentode......Page 106
The Cascode......Page 109
The Charge Amplifier......Page 117
The Cathode Follower......Page 118
Sources and Sinks: Definitions......Page 122
The Common Cathode Amplifier as a Constant Current Sink (CCS)......Page 124
Pentode Constant Current Sinks......Page 126
The Cathode Follower with Active Load......Page 128
Analysis of the Self-Contained White Cathode Follower......Page 129
The White Cathode Follower as an Output Stage......Page 132
The μ-Follower......Page 133
Upper Valve Choice in the μ-Follower......Page 137
Limitations of the μ-Follower......Page 138
The Shunt-Regulated Push–Pull Amplifier (SRPP)......Page 140
The β-Follower......Page 143
The Cathode-Coupled Amplifier......Page 145
The Differential Pair......Page 148
Output Resistance of the Differential Pair......Page 150
Common-Mode Rejection Ratio (CMRR)......Page 151
Power Supply Rejection Ratio (PSRR)......Page 153
Semiconductor Constant Current Sinks......Page 154
Using Transistors as Active Loads for Valves......Page 157
Optimising rout by Choice of Transistor Type......Page 160
Field-Effect Transistors (FETs) as Constant Current Sinks......Page 162
Designing Constant Current Sinks Using the DN2540N5......Page 164
References......Page 168
Recommended Further Reading......Page 169
Defining Distortion......Page 170
Measuring Non-Linear Distortion......Page 171
Distortion Measurement and Interpretation......Page 172
Choosing the Measurement......Page 173
Weighting of Harmonics......Page 174
Summation and Rectifiers......Page 175
Noise and THD+N......Page 177
Digital Concepts......Page 178
Scaling......Page 179
Precision......Page 180
The Fast Fourier Transform (FFT)......Page 181
Windowing......Page 182
How the Author’s Distortion Measurements Were Made......Page 183
Signal Amplitude......Page 184
Cascodes and Distortion......Page 187
Distortion due to Grid Current at Contact Potential......Page 188
Distortion due to Grid Current and Volume Controls......Page 189
Operating with Grid Current (Class A2)......Page 190
Distortion Reduction by Parameter Restriction......Page 192
Distortion Reduction by Cancellation......Page 195
Differential Pair Distortion Cancellation......Page 197
The Western Electric Harmonic Equaliser......Page 199
Side-Effects of the Harmonic Equaliser......Page 201
Cathode Resistor Bias......Page 203
Grid Bias (Rk=0)......Page 205
Diode Cathode Bias (rk≈0)......Page 206
Constant Current Sink Bias......Page 210
Which Valves Were Explicitly Designed to be Low Distortion?......Page 211
Deflecting Electrons......Page 213
The Test Circuit......Page 214
Test Results......Page 215
Interpretation......Page 218
Alternative Medium-μ Valves......Page 220
Overall Conclusions......Page 221
Coupling from One Stage to the Next......Page 222
Blocking......Page 223
Low Frequency Step Networks......Page 225
Level Shifting and DC Coupling......Page 226
A DC Coupled Class A Electromagnetic Headphone Amplifier......Page 228
Using a Norton Level Shifter......Page 231
Distortion and Negative Feedback......Page 234
Noise......Page 237
Noise from Resistive Volume Controls......Page 238
Noise from Amplifying Devices......Page 239
Electrometers and Grid Current......Page 241
How the Author’s DC Reference Noise Measurements Were Made......Page 245
Semiconductor Reference Noise Measurements and Statistical Summation......Page 247
Variation of Zener Reference Noise with Operating Current......Page 249
Noise of the Composite Zener Compared to a 317......Page 250
References......Page 251
Recommended Further Reading......Page 252
Preferred Values......Page 254
Heat......Page 255
Metal Film Resistors......Page 256
Ageing Wirewound Resistors......Page 259
Noise and Inductance of Wirewound Resistors......Page 260
Heat......Page 263
The Parallel Plate Capacitor......Page 264
The Dielectric......Page 265
Different Types of Capacitors......Page 266
Plastic Film, Foil Plate Capacitors (2<εr<4)......Page 268
Metallised Paper Capacitors (1.8<εr<6)......Page 271
Ceramic Capacitors......Page 272
Aluminium Electrolytic Capacitors (εr≈8.5)......Page 273
Tantalum Electrolytic Capacitors (εr≈25)......Page 281
Imaginary Capacitance......Page 282
Capacitance Value......Page 284
Microphony......Page 285
Bypassing......Page 286
Magnetic Components......Page 287
Air-Cored Inductors......Page 288
Gapped Cores for AC Only......Page 290
Gapped Cores for AC and DC (Power Supply Chokes)......Page 291
Self-Capacitance......Page 292
Iron Losses......Page 294
DC Magnetisation......Page 298
Electrostatic Screens......Page 299
Output Transformers, Feedback and Loudspeakers......Page 300
Transformer Models......Page 301
Input Transformer Loading......Page 304
Why Should I Use a Transformer?......Page 306
General Considerations in Choosing Transformers......Page 307
Guitar Amplifiers and Arcs......Page 308
Magnetic Core Deterioration......Page 309
History......Page 310
Emission......Page 311
Electron Velocity......Page 312
Transit Time......Page 313
The Cathode......Page 314
Thoriated Tungsten Filament Fragility......Page 317
The Thermal Problem......Page 318
The Indirectly Heated Cathode Solution......Page 319
Heater/Cathode Insulation......Page 320
Heaters and their Supplies......Page 322
Current Hogging and Heater Power......Page 324
Heater Voltage and Current......Page 326
The Control Grid......Page 329
Grid Emission......Page 330
Frame-Grid Valves......Page 331
Variable-μ Grids and Distortion......Page 332
Other Grids......Page 333
The Anode......Page 334
The Vacuum and Ionisation Noise......Page 337
The Getter......Page 338
The Mica Wafers and Envelope Temperature......Page 339
Valve Bases and the Loktal™ Base......Page 341
The Glass Envelope and the Pins......Page 343
PCB Materials......Page 344
References......Page 345
Recommended Further Reading......Page 346
The Major Blocks......Page 348
Choice of Rectifiers/Diodes......Page 349
Rectifiers To Be Avoided (Gas)......Page 355
Rectifiers To Be Avoided (Copper Oxide)......Page 357
The Single Reservoir Capacitor Approach......Page 358
Ripple Voltage......Page 359
The Effect of Ripple Voltage on Output Voltage......Page 360
Ripple Current and Conduction Angle......Page 361
Choosing the Reservoir Capacitor and Transformer......Page 365
Back-to-Back Mains Transformers for HT Supplies......Page 368
Voltage Multipliers......Page 370
The Choke Input Power Supply......Page 372
Minimum Load Current for a Choke Input Supply......Page 373
Current Rating of the Choke......Page 374
Current Spikes and Snubbers......Page 376
Intermediate Mode: The Region Between Choke Input and Capacitor Input......Page 380
PSUD2......Page 382
Region 1......Page 384
Region 4......Page 386
Estimation of Wide-Band LC Response......Page 390
Sectioned RC Filters......Page 391
Regulators......Page 393
The Fundamental Series Regulator......Page 394
The Two-Transistor Series Regulator......Page 396
The Speed-Up Capacitor......Page 397
A Variable Bias Voltage Regulator......Page 399
The 317 IC Voltage Regulator......Page 401
The 317 as an HT Regulator......Page 403
Valve Voltage Regulators......Page 405
Optimised Valve Voltage Regulators......Page 408
Increasing Output Current Cheaply......Page 409
Power Supply Output Resistance and Stereo Crosstalk......Page 412
Power Supply Output Resistance and Amplifier Stability......Page 413
The Statistical Regulator......Page 414
Bypassing the Composite Zener......Page 417
Optimising the Statistical Regulator......Page 419
References for Elevated Heater Supplies – the THINGY......Page 420
Heaters and History......Page 423
Mains Transformers and Inter-Winding Capacitance......Page 424
Reducing Transformer Inter-Winding Capacitance......Page 425
Post-Transformer Filtering......Page 426
Transformer Regulation......Page 427
HT Capacitors and Voltage Ratings......Page 428
Can Potentials and Undischarged HT Capacitors......Page 429
Mains Fusing......Page 430
Mains Switching......Page 431
A Practical Design......Page 432
HT Regulation......Page 433
HT Rectification and Smoothing (a PSUD2 Exercise)......Page 435
Heater Rectification and Smoothing (a Manual Exercise)......Page 438
Heater Regulation......Page 439
Mains Filtering......Page 440
Adapting the Power Supply to the EC8010 RIAA Stage......Page 441
HT Regulation......Page 443
HT Rectification and Smoothing (a PSUD2 Exercise)......Page 444
Heater Regulation......Page 446
Heater Rectification and Smoothing (a Manual Exercise)......Page 447
References......Page 448
Recommended Further Reading......Page 449
The Output Stage......Page 450
The Single-Ended Class A Output Stage......Page 451
The Significance of High Output Resistance......Page 453
Transformer Imperfections......Page 454
Class C......Page 456
The Push–Pull Output Stage and the Output Transformer......Page 458
Modifying the Connection of the Output Transformer......Page 461
The Entire Amplifier......Page 465
The Driver Stage......Page 467
The Phase Splitter......Page 469
The Differential Pair and Its Derivatives......Page 470
The Input Stage......Page 479
Slugging the Dominant Pole......Page 480
Low Frequency Instability, or Motorboating......Page 482
Parasitic Oscillation and Control Grid-Stoppers......Page 483
Stability Margin......Page 484
The Williamson......Page 485
The Mullard 5-20......Page 487
The Quad II......Page 492
The Scrapbox Challenge Single-Ended Amplifier......Page 495
Choice of Output Valve......Page 496
Choosing the DC Operating Point by Considering Output Power and Distortion......Page 497
Biassing the Valve......Page 498
The Cathode Bypass Capacitor......Page 499
HT Rectification......Page 500
The HT Transformer......Page 501
HT Choke Suitability......Page 502
The HT Regulator Option......Page 503
Estimating Amplifier Output Resistance......Page 505
Driver Stage Topology......Page 506
Determining the Driver Stage Operating Point......Page 507
Is the Output Resistance and Gain of the Proposed Driver Stage Adequate?......Page 508
Teething Problems......Page 509
Designer’s Observations......Page 512
Conclusions......Page 513
Sex, Lies and Output Power......Page 515
Active Crossovers and Zobel Networks......Page 516
Parallel Output Valves and Transformer Design......Page 518
Driving Higher Power Output Stages......Page 519
The Crystal Palace Amplifier......Page 520
13E1 Conditions......Page 522
(3) Push–pull Output with Good Balance......Page 525
(8) Tolerance of Output Stage Conduction Angle Changes from 360° to 0°......Page 526
Circuit Topology: Power Supplies and Their Effect on Constant Current Sinks......Page 527
Va(max) and the Positive HT Supply......Page 528
The Second Differential Pair and Output Stage Current......Page 529
Why Not Have Tighter Stabilisation?......Page 530
Valve Matching......Page 532
The Cascode Constant Current Sink and Stabilisation Against Mains Variation......Page 533
The 334Z Constant Current Sink and Thermal Stability......Page 536
HT Regulators......Page 537
Power Supply Design......Page 539
Exceeding Vg2......Page 540
Global Negative Feedback......Page 542
Background......Page 546
Comparing Cathode and FET Source Followers......Page 548
Output Stage Bias, Balance and Coupling......Page 551
Gain Stage CCS and Gain Balance......Page 554
Balanced Inputs on Power Amplifiers......Page 555
The Volume Control and Baffle Step Compensation......Page 556
Audio Circuit Comments......Page 557
Power Supplies......Page 558
References......Page 560
Further reading......Page 561
7. The Pre-Amplifier......Page 562
Disparate Levels between Sources......Page 563
Adjacent Contact Capacitance (Crosstalk Between Sources)......Page 564
Solutions and Problems Peculiar to Electromechanical Switches (Relays)......Page 565
Volume Control......Page 566
Limitations on the Control’s Value (Disturbing Frequency Response)......Page 567
Logarithmic Law (Perceived Volume Not Changing Smoothly with Rotation)......Page 568
Switched Attenuators (Disturbing Channel Matching)......Page 569
Switched Attenuator Design......Page 570
Spreadsheets and Volume Controls......Page 573
Volume Controls for Digital Active Crossovers......Page 574
Volume Control Values and Their Effect on Noise......Page 577
Grid-Leak Resistors and Volume Controls......Page 578
Light-Sensitive Resistors as Volume Controls......Page 580
Transformer Volume Controls......Page 582
Law Faking......Page 583
Determination of Required Quiescent Current......Page 587
Choice of Follower Valve......Page 589
Practical Considerations......Page 590
Adding Gain......Page 592
Polarity Inversion......Page 593
Tone Control......Page 594
Comparison of Analogue Levels between Vinyl and Digital Sources......Page 600
RIAA and Replay Rumble......Page 601
The Mechanical Problem......Page 602
Arm Wiring and Moving Coil Cartridge DC Resistance......Page 603
Balanced Working and Pick-Up Arm Wiring......Page 604
RIAA Stage Design......Page 606
Determination of Requirements......Page 607
Implementing RIAA Equalisation......Page 609
‘All in One Go’ Equalisation......Page 611
Split RIAA Equalisation......Page 612
Noise and Input Capacitance of the Input Stage......Page 614
Valve Noise......Page 620
Connecting Devices in Parallel to Reduce noise......Page 621
Noise Advantage due to RIAA Equalisation......Page 622
Calculation of Component Values for 75μs......Page 623
180μs, 318μs Equalisation and the Problem of Interaction......Page 625
3180μs and 318μs Equalisation......Page 626
Awkward Values and Tolerances......Page 627
The Input Stage......Page 629
Optimising the Input Transformer......Page 632
The Second Stage......Page 633
Refining Valve Choice by Heaters......Page 634
Grid Current Distortion and RIAA Equaliser Series Resistances......Page 635
The 75μs Problem......Page 636
3180μs, 318μs Pairing Manipulation......Page 637
75μs/3.18μs Manipulation......Page 638
RIAA Direct Measurement Problems......Page 639
Production Tolerances and Component Selection......Page 642
The Balanced Hybrid RIAA Stage......Page 643
Semiconductors to the Rescue......Page 644
Miller Capacitance......Page 645
JFET Noise......Page 646
BJT Noise......Page 647
Choosing between the BJT and JFET: Equalisation, Distortion and HT Power......Page 648
Implications of the Block Diagram......Page 649
The Unity-Gain Cable Drivers......Page 650
Deciding the HT Voltage......Page 651
Input Stage BJT Miller Capacitance......Page 652
VCE and BJT Linearity......Page 653
Input Resistance and Bias Current......Page 654
Input Stage Noise......Page 655
RIAA Calculations......Page 656
The Source Followers......Page 657
The HT Supply......Page 658
Summary......Page 660
Recommended Further Reading......Page 661
Valve Data......Page 662
Resistor Colour Code......Page 666
Cable......Page 668
Square Wave Sag and Low Frequency f–3 dB......Page 669
Playing 78s......Page 671
Equalisation......Page 672
CD......Page 674
Sourcing Components: Bargains and Dealing Directly......Page 675
References......Page 677
Index......Page 678

✦ Subjects

Nonfiction