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Audio Power Amplifier Design, 6th Edition

Book Description

This book is essential for audio power amplifier designers and engineers for one simple reason...it enables you as a professional to develop reliable, high-performance circuits. The Author Douglas Self covers the major issues of distortion and linearity, power supplies, overload, DC-protection and reactive loading. He also tackles unusual forms of compensation and distortion produced by capacitors and fuses.

This completely updated fifth edition includes four NEW chapters including one on The XD Principle, invented by the author, and used by Cambridge Audio. Crosstalk, power amplifier input systems, and microcontrollers in amplifiers are also now discussed in this fifth edition, making this book a must-have for audio power amplifier professionals and audiophiles.

Table of Contents

  1. Cover
  2. Half Title
  3. Title Page
  4. Copyright Page
  5. Bound to Create
  6. Dedication
  7. Table of Contents
  8. Preface to the Sixth Edition
  9. Acknowledgements
  10. List of Abbreviations
  11. Chapter 1 Amplifiers and The Audio Signal
    1. The Economic Importance of Power Amplifiers
    2. Assumptions
    3. Origins and Aims
    4. The Study of Amplifier Design
    5. The Characteristics of the Audio Signal
      1. Amplitude Distribution with Time
      2. Amplitude Distribution with Frequency
    6. The Performance Requirements for Amplifiers
      1. Safety
      2. Reliability
      3. Power Output
      4. Frequency Response
      5. Noise
      6. Distortion
      7. “Damping Factor”
      8. Absolute Phase
    7. Amplifier Formats
    8. Misinformation in Audio
    9. Science and Subjectivism
      1. The Subjectivist Position
      2. A Short History of Subjectivism
      3. The Limits of Hearing
      4. The Limits of Hearing: Phase Perception.
    10. Articles of Faith: The Tenets of Subjectivism
      1. The Length of the Audio Chain
      2. The Implications
      3. The Reasons Why
      4. The Outlook
      5. Technical Errors
    11. References
  12. Chapter 2 The Basics of Distortion
    1. Models of Non-linearity
    2. Cubic Distortion
    3. Cubic + Linear Distortion
    4. Square Law Distortion
    5. Square Root Distortion
    6. Soft-clipping Distortion
    7. Hard-clipping Distortion: Symmetrical
    8. Hard-clipping Distortion: Asymmetrical
    9. Crossover Distortion Modelling
    10. Other Distortion Models
    11. Choosing a Distortion Model
    12. SPICE Models for Passive Components
    13. First-order Voltage-coefficient Distortion Model
    14. Second-order Voltage-coefficient Distortion Model
    15. Other Voltage Coefficient Distortion Models
    16. Measuring Resistor Distortion
      1. Metal Film, Metal Foil, and Wirewound Resistors
      2. Metal Oxide Resistors
      3. Carbon Film Resistors
      4. Carbon Film Resistor Usage
      5. Carbon Composition Resistors
    17. Resistors in the Feedback Network
    18. Modelling Distortion from other Passive Components
    19. References
  13. Chapter 3 Negative Feedback
    1. Negative Feedback in Amplifiers
    2. Common Misconceptions about Negative Feedback
    3. Negative Feedback and Amplifier Stability
    4. Feedback Intermodulation Distortion
    5. Maximising the Amount of Negative Feedback
    6. Overall Feedback Versus Local Feedback
    7. Maximising Linearity before Feedback
    8. Positive Feedback in Amplifiers
    9. References
  14. Chapter 4 Amplifier Architecture, Classes, and Variations
    1. Amplifier Architectures
    2. The Three-stage Amplifier Architecture
    3. The Two-stage Amplifier Architecture
    4. The Four-stage Amplifier Architecture
    5. The Five-stage Amplifier Architecture
    6. Power Amplifier Operating Classes
    7. Combinations of Amplifier Classes
      1. Class-A
      2. Class-AB
      3. Class-B
      4. Class-C
      5. Class-D
      6. Class-E
      7. Class-F
      8. Class-G
      9. Class-H
      10. Class-S
      11. Class XD
      12. Edwin Amplifiers
      13. The Limits of Classification
    8. Amplifier Variations
      1. Error-correcting Amplifiers
      2. Auxiliary Amplifiers
      3. Non-switching Amplifiers
      4. The Blomley Principle
      5. Ribbon Loudspeaker Amplifiers
      6. Power Amplifiers Combined with Tone-controls
      7. Opamp Array Amplifiers
      8. Current-drive Amplifiers
    9. Amplifier Bridging
      1. Fractional Bridging
      2. Eliminating the Bridging Inverter
      3. Increasing Bridging Reliability
    10. AC- and DC-coupled Amplifiers
      1. The Advantages of AC-coupling
      2. The Advantages of DC-coupling
    11. References
    12. Further reading
  15. Chapter 5 General Principles and Distortion Mechanisms
    1. Gain and Feedback in the Three-stage Amplifier
    2. The Advantages of the Conventional
    3. The Distortion Mechanisms
      1. Distortion One: Input Stage Distortion
      2. Distortion Two: VAS Distortion
      3. Distortion Three: Output Stage Distortion
      4. Distortion Four: VAS Loading Distortion
      5. Distortion Five: Rail Decoupling Distortion
      6. Distortion Six: Induction Distortion
      7. Distortion Seven: NFB Takeoff Distortion
      8. Distortion Eight: Capacitor Distortion
      9. Distortion Nine: Magnetic Distortion
      10. Distortion Ten: Input Current Distortion
      11. Distortion Eleven: Premature Overload Protection Distortion
    4. Non-existent or Negligible Distortions
    5. The Performance of a Standard Amplifier
    6. Open-loop Linearity and How to Determine It
    7. Direct Open-loop Gain Measurement
    8. Using Model Amplifiers
    9. The Concept of the Blameless Amplifier
    10. References
  16. Chapter 6 The Input Stage
    1. The Role of the Input Stage
    2. Distortion from the Input Stage
    3. BJTs vs FETs for the Input Stage
      1. Advantages of the FET Input Stage
      2. Disadvantages of the FET Input Stage
    4. Singleton Input Stage Versus Differential Pair
    5. The Input Stage Distortion in Isolation
    6. Input Stage Balance
    7. The Joy of Current-mirrors
    8. Better Current-mirrors
    9. Improving Input Stage Linearity
    10. Further Improving Input-Stage Linearity
    11. Increasing the Output Capability
    12. Input Stage Cascode Configurations
    13. Double Input Stages
    14. Input Stage Common-mode Distortion
    15. Input Current Distortion
    16. Noise
      1. Noise Sources in Power Amplifiers
      2. Noise in Bipolar Transistors
      3. Reducing Input Transistor Noise
    17. Offset and Match: The DC Precision Issue
    18. The Input Stage and the Slew-rate
    19. Input Stage Conclusions
    20. References
  17. Chapter 7 The Voltage-Amplifier Stage
    1. The Voltage-Amplifier Stage (VAS)
    2. The Naming of Parts
    3. The Basic Single-ended VAS
    4. Bootstrapping the VAS
    5. The Current-source VAS
    6. VAS Operation and Open-loop Gain
    7. The Simple VAS in a Model Amplifier
    8. The Mechanisms of VAS Distortion
      1. HF Distortion from the VAS Transistor Cbc
      2. Changing the Amplifier Operating Point
      3. Changing the Supply Rails
      4. The Dual VAS
      5. VAS Distortion from Clamp Diodes
      6. The History of Non-linear Cbc Distortion
      7. LF Distortion Due to VAS Transistor Early Effect
      8. Early Effect in the Simple VAS
      9. The Simulation of Simple VAS Early Effect Distortion
    9. Methods for The Reduction of VAS Distortion
    10. The Emitter-follower VAS
      1. How the EF-VAS Works
      2. A Brief History of the EF-VAS
      3. Clamp Diodes and the EF-VAS
      4. The Benefits of the EF-VAS
    11. The Cascode VAS
      1. How the Cascode VAS Works
      2. A Brief History of the Cascode VAS
      3. The Benefits of the Cascode VAS
    12. The VAS Buffer
    13. VAS Distortion Due to Output Stage Loading
    14. Some More VAS Variations
    15. VAS Operating Conditions
    16. VAS Current Limiting
    17. The Class-AB VAS and Further Developments
    18. Manipulating Open-loop Bandwidth
    19. Conclusions
    20. References
  18. Chapter 8 The Push-pull Voltage-Amplifier Stage
    1. The Push-pull VAS
    2. Single Input Stages with a Push-pull VAS
    3. The Hitachi Push-pull VAS
    4. The Hitachi Push-pull VAS: Heating and Drift
    5. The Hitachi Circuit: AC Gain
    6. The Hitachi push-pull VAS: distortion
    7. The Hitachi Push-pull VAS: Asymmetrical Clipping
    8. The Lender Push-pull VAS
    9. The Lender Push-pull VAS: Heating and Drift
    10. Single Input Stages with a One-input Push-pull VAS
    11. The Series Input Stage Push-pull VAS
    12. Single-input Push-pull VAS Circuits: Conclusions
    13. The Double Input Stage Push-pull Simple VAS
    14. The Double Input Stage Push-pull Simple VAS: Open-loop Gain
    15. The Double Input Stage Push-pull Simple VAS: Distortion
    16. The Double Input Stage Push-pull Simple VAS: Noise
    17. The Double Input Stage Push-pull Simple VAS: PSRR
    18. A Brief History of the Double Input Stage Push-pull VAS
    19. The Double Input Stage Push-pull EF-VAS
    20. The Double Input Stage Push-pull EF-VAS: Open-loop Gain
    21. The Double Input Stage Push-pull EF-VAS: Distortion
    22. The Double Input Stage Push-pull EF-VAS: Slew-rate
    23. The Double Input Stage with Mirrors and Push-pull Simple VAS
    24. The Double Input Stage Push-pull VAS: Conclusions
    25. A More Advanced Push-pull VAS
    26. The Folded-cascode VAS
    27. The Push-pull VAS: Final Conclusions
    28. References
  19. Chapter 9 The Output Stage
    1. Classes and Devices
    2. The Distortions of the Output
      1. Harmonic Generation by Crossover Distortion
      2. Comparing Output Stages
    3. The Emitter-follower Output
      1. Multiple Output Devices: EF Output
    4. The CFP Output
      1. Multiple Output Devices: CFP Output
    5. Output Stages with Gain
    6. Quasi-complementary Outputs
    7. Triple-based Output Configurations
      1. Triple EF Output Stages
    8. Quadruple Output Stages
    9. Series Output Stages
    10. Selecting an Output Stage
    11. Output Stage Conclusions
    12. References
  20. Chapter 10 Output Stage Distortions
    1. Output Stage Distortions and their Mechanisms
    2. Large-signal Distortion (Distortion 3a)
      1. The Load-Invariant Concept
      2. The LSN Mechanism
      3. LSN with Doubled Output Devices
      4. LSN with Better Output Devices
      5. LSN with Feedforward Diodes
      6. LSN with Triple Output Stages
      7. Loads below 4 Ω
      8. Better 8 Ω Performance
      9. A Practical Load-Invariant Design
      10. More on Multiple Output Devices
      11. Load Invariance: Summary
    3. Crossover Distortion (Distortion 3b)
      1. Output Stage Quiescent Conditions
      2. An Experiment on Crossover Distortion
      3. Vq as the Critical Quiescent Parameter
    4. Switching Distortion (Distortion 3c)
    5. Thermal Distortion
    6. Thermal Distortion in a Power Amp IC
    7. Closing the Loop: Distortion in Complete Amplifiers
    8. Reference
  21. Chapter 11 More Distortion Mechanisms
    1. Distortion Four: VAS Loading Distortion
    2. Distortion Five: Rail Decoupling Distortion
    3. Distortion Six: Induction Distortion
    4. Distortion Seven: NFB Takeoff Point Distortion
    5. Distortion Eight: Capacitor Distortion
    6. Distortion Nine: Magnetic Distortion
    7. Distortion Ten: Input Current Distortion
    8. Distortion Eleven: Premature Overload Protection
    9. Design Example: a 50 W Class-B Amplifier
    10. References
  22. Chapter 12 Closely Observed Amplifiers: Design Examples
    1. Amplifier Design Examples
    2. Amplifier 1: EF-VAS, CFP Output Stage, Miller Compensation
    3. Amplifier 2: Simple VAS, CFP Output Stage, Miller Compensation
    4. Amplifier 3: EF-VAS, CFP Output Stage, Inclusive Compensation
    5. Amplifier 4: EF-VAS, CFP Output Stage, Miller Compensation
    6. Amplifier 5: EF-VAS, CFP Output Stage, Inclusive Compensation
    7. Conclusions
    8. References
  23. Chapter 13 Compensation and Stability
    1. Compensation and Stability
    2. Dominant Pole Compensation
    3. Maximal Negative Feedback
    4. Dominant Pole Miller Compensation
    5. Dominant Pole Miller Compensation at High Gains
    6. Dominant Pole Shunt Compensation
    7. Output-inclusive Compensation
      1. The Problems of Output Inclusion
      2. Input-inclusive Compensation
      3. Stable Output-inclusive Compensation: The History
      4. Stable Output-inclusive Compensation: Implementation
      5. Experimenting with Output-inclusive Compensation
      6. Ultra-low Distortion Performance Comparisons
    8. Two-pole Compensation
      1. Factors Affecting the Two-pole Loop-gain Response
      2. Effect of Two-pole Compensation on the Closed-loop Gain
      3. Eliminating the Two-pole Midband Loop-gain Peak
      4. Two-pole Compensation and PSRR
      5. Two-pole Compensation: Summary
      6. Combining Two-pole and Output-inclusive Compensation
    9. Other Forms of Compensation
    10. Stability and VAS-collector-to-ground Capacitance
    11. Nested Feedback Loops
    12. Nested Differentiating Feedback Loops
    13. References
  24. Chapter 14 Output Networks and Load Effects
    1. Output Networks
    2. Amplifier Output Impedance
    3. Minimising Amplifier Output Impedance
    4. Zobel Networks
    5. Output Inductors
    6. Designing the Output Inductor: Single-layer Coils
    7. Designing the Output Inductor: Multi-layer Coils
    8. Crosstalk in Amplifier Output Inductors
      1. Coil Crosstalk Conclusions
    9. Coil Placement Issues
    10. Cable Impedance Effects
    11. Reactive Loads and Speaker Simulation
      1. Resistive Loads
      2. Modelling Real Loudspeaker Loading
    12. Loudspeaker Loads and Output Stages
      1. Single-speaker Load
      2. Two-way Speaker Loads
    13. Enhanced Loudspeaker Currents
    14. Amplifier Stability
      1. HF Instability
      2. LF Instability
    15. References
  25. Chapter 15 Speed and Slew-rate
    1. Speed and Slew-rate in Audio Amplifiers
    2. The Basics of Amplifier Slew-limiting
    3. Slew-rate Measurement Techniques
    4. Improving the Slew-rate
    5. Simulating Slew-limiting
    6. Slewing Limitations in Real Life
    7. Some Additional Complications
    8. On Asymmetrical Slew-rates
    9. Further Improvements and other Configurations
    10. References
  26. Chapter 16 Power Dissipation in Amplifiers
    1. Output Stage Conditions
    2. The Mathematical Approach
    3. Dissipation by Simulation
    4. Power Partition Diagrams
      1. Class-B: CFP and EF Power Partition
      2. Class-AB Power Partition
      3. Class-A Power Partition
      4. Class XD Power Partition: Constant-current and Push-pull
      5. Class-G Power Partition
      6. Class-B EF with Reactive Loads
      7. Conclusions on Reactive Loads
    5. The Peak-to-Mean Ratio of Music
    6. The Probability Density Function (PDF)
    7. The Cumulative Distribution Function (CDF)
    8. Measuring the PDF
    9. Deriving the Actual Power Dissipation
    10. Actual Power Dissipation for Class-B CFP
    11. Actual Power Dissipation for Class-AB
    12. Actual Power Dissipation for Class-A Push-pull
    13. Actual Power Dissipation for Class-G
    14. Actual Power Dissipation with Reactive Loads
    15. Dissipation Summary
    16. A Power Amplifier Design Procedure
    17. Design Procedure Results
    18. References
  27. Chapter 17 Class-A Power Amplifiers
    1. An Introduction to Class-A
    2. Class-A Configurations and Efficiency
    3. Output Stages in Class-A
    4. Quiescent Current Control Systems
    5. A Novel Quiescent Current Controller
    6. A Class-A Design
    7. The Trimodal Amplifier
    8. Load Impedance and Operating Mode
    9. Efficiency
    10. On Trimodal Biasing
    11. Class-A/AB Mode
    12. Class-B Mode
    13. The Mode-switching System
    14. Thermal Design
    15. A Complete Trimodal Amplifier Circuit
    16. The Power Supply
    17. The Performance
    18. Further Possibilities
    19. References
  28. Chapter 18 Class XD: Crossover Displacement.
    1. The Crossover Displacement Principle
    2. Crossover Displacement Realisation
    3. Circuit Techniques for Crossover Displacement
    4. A Complete Crossover Displacement Power Amplifier Circuit
    5. The Measured Performance
    6. The Effect of Loading Changes
    7. The Efficiency of Crossover Displacement
    8. Other Methods of Push-pull Displacement Control
    9. Summary: Advantages and Disadvantages
    10. References
  29. Chapter 19 Class-G Power Amplifiers
    1. The Principles of Class-G
    2. Introducing Series Class-G
    3. Efficiency of Class-G
    4. Practicalities
    5. The Biasing Requirements
    6. The Linearity Issues of Series Class-G
    7. The Static Linearity
    8. Practical Class-G Design
    9. Controlling Small-Signal Distortion
    10. The Performance
    11. Deriving a New Kind of Amplifier: Class-A + C
    12. Class-G with Two-pole Compensation
    13. Class-G with Output-inclusive Compensation
    14. Class-G Mode Indication
    15. Further Variations on Class-G
    16. References
  30. Chapter 20 Class-D Power Amplifiers
    1. A Bit of History
    2. Basic Principles
    3. Class-D Technology
    4. Output Filters
    5. Negative Feedback in Class-D
    6. Protection
    7. Efficiency
    8. Alternative Modulation Systems
    9. Class-D Examples
    10. Further Development
    11. References
  31. Chapter 21 FET Output Stages
    1. The Characteristics of Power FETS
    2. FET versus BJT Output Stages
      1. Advantages of FETs
      2. Disadvantages of FETs
    3. IGBTs
    4. Power FET Output Stages
    5. Power FETs and Bipolars: the Linearity Competition
    6. FETs in Class-A Stages
    7. References
  32. Chapter 22 Thermal Compensation and Thermal Dynamics
    1. Why Quiescent Conditions are Critical
    2. Accuracy Required of Thermal Compensation
    3. Basic Thermal Compensation
    4. Assessing the Bias Errors
    5. Thermal Simulation
    6. Modelling the EF Output Stage
    7. Modelling the CFP Output Stage
    8. The Integrated Absolute Error Criterion
    9. Improved Thermal Compensation: the Emitter-follower Stage
    10. Improved Compensation for the CFP Output Stage
    11. A Better Sensor Position
    12. A Junction-temperature Estimator
    13. A Junction Estimator with Dynamics
    14. Conclusions about the Simulations
    15. Power Transistors with Integral Temperature Sensors
    16. Variable-tempco Bias Generators
      1. Creating a Higher Tempco
      2. Ambient Temperature Changes
      3. Creating a Lower Tempco
      4. Current Compensation
      5. Early Effect in Output Stages
    17. Thermal Dynamics by Experiment
      1. Crossover Distortion Against Time: Some Results
    18. More Measurements: Conventional and ThermalTrak
    19. References
  33. Chapter 23 The Design of DC Servos
    1. DC Offset Trimming
    2. DC Offset Control by Servo-loop
      1. Advantages of DC Servos
    3. Basic Servo Configurations
    4. Noise, Component Values, and the Roll-off
    5. Non-inverting Integrators
      1. The 2C Integrator
      2. The 1C Integrator
    6. Choice of Integrator
    7. Choice of Opamps
    8. Servo Authority
    9. Design of LF Roll-off Point
    10. Servo Overload
    11. Servo Testing
    12. Performance Issues
    13. Multipole Servos
  34. Chapter 24 Amplifier and Loudspeaker Protection
    1. Categories of Amplifier Protection
    2. Semiconductor Failure Modes
    3. Overload Protection
      1. Overload Protection by Fuses
      2. Electronic Overload Protection
      3. Plotting the Protection Locus
      4. Simple Current-limiting
      5. Single-slope VI Limiting
      6. Dual-slope VI limiting
      7. Time-dependent VI Limiting
      8. Alternative VI-limiter Implementations
      9. VI Limiting and Temperature Effects
      10. Simulating Overload Protection Systems
      11. Testing the Overload Protection
      12. Speaker Short-circuit Detection
    4. Catching Diodes
    5. DC-offset Protection
      1. DC-offset Protection by Fuses
      2. Relay DC-offset Protection and Muting Control
      3. Filtering for DC Protection
      4. The Single RC Filter
      5. The Dual RC Filter
      6. The Second-order Active Filter
      7. Bidirectional DC Detection
      8. Output Relay Selection
      9. Distortion from Output Relays
      10. Output Crowbar DC Protection
      11. Protection by Power-supply Shutdown
      12. Testing DC-offset protection
    6. Thermal Protection
    7. Output Transient Suppression
    8. Clip Detection
      1. Clip Detection by Rail-approach Sensing
      2. Clip Detection by Input-output Comparison
    9. Amplifier Protection Patents
    10. Powering Auxiliary Circuitry
    11. References
  35. Chapter 25 Layout, Grounding, and Cooling
    1. Audio Amplifier PCB Design
      1. Crosstalk
      2. Rail Induction Distortion
      3. The Mounting of Output Devices
      4. Single and Double-sided PCBs
      5. PCB Track Resistance and How to Reduce it
      6. Cable Resistance
      7. Power Supply PCB Layout
      8. Power Amplifier PCB Layout Details
      9. The Audio PCB Layout Sequence
    2. Amplifier Grounding
    3. Ground Loops: How they Work and How to Deal with them
      1. Hum Injection by Mains Grounding Currents
      2. Hum Injection by Transformer Stray Magnetic Fields
      3. Hum Injection by Transformer Stray Capacitance
      4. Ground Currents Inside Equipment
      5. Balanced Mains Power
    4. Class I and Class II
      1. Warning
    5. Cooling
      1. Convection Cooling
      2. Fan Cooling
      3. Heat Pipes
    6. Mechanical Layout and Design Considerations
      1. Wiring Layout
      2. Semiconductor Installation
    7. Reference
  36. Chapter 26 Power Supplies and PSRR
    1. Power Supply Technologies
      1. Simple Unregulated Power Supplies
      2. Linear Regulated Power Supplies
      3. Switch-mode Power Supplies
    2. A Devious Alternative to Regulated Power Supplies
    3. Design Considerations for Power Supplies
      1. Mains Connectors
      2. Mains Transformers
      3. Transformers and Hum
      4. External Power Supplies
      5. Inrush Currents
      6. Fusing
      7. Rectification
      8. RF Emissions from Bridge Rectifiers
      9. Relay Supplies
    4. Power Supply-rail Rejection in Amplifiers
      1. A Design Philosophy for Supply-rail Rejection
      2. Positive Supply-rail Rejection
      3. Negative Supply-rail Rejection
    5. References
  37. Chapter 27 Power Amplifier Input Systems
    1. External Signal Levels
    2. Internal Signal Levels
    3. Unbalanced Inputs
    4. Balanced Interconnections
      1. Balanced Connectors
    5. Balanced Inputs: Electronic vs Transformer
    6. Balanced Inputs and their Common-Mode Rejection Ratio
    7. The Basic Balanced Input
    8. Practical Common-Mode Rejection
    9. The Practical Balanced Input
    10. Combined Unbalanced and Balanced Inputs
    11. Variable-gain Balanced Inputs
    12. The Instrumentation Amplifier
    13. Transformer Balanced Inputs
    14. Input Overvoltage Protection
    15. Noise and the Input System
    16. Low-noise Balanced Inputs
    17. The Choice of Opamps
    18. Using an Internal Balanced Power Amplifier Interface
    19. References
  38. Chapter 28 Input Processing and Auxiliary Systems
    1. Ground Lift Switches
    2. Phase Reversal Facility
    3. Gain Control
    4. Subsonic Filtering: High-pass
    5. Ultrasonic Filtering: Low-pass
    6. Combined Filters
    7. Electronic Crossovers
    8. Digital Signal Processing
    9. Signal-present Indication
    10. Output Level Indication
    11. Signal Activation
    12. 12 V Trigger Activation
    13. Infra-red Remote Control
    14. Other Amplifier Facilities
    15. References
  39. Chapter 29 Testing and Safety.
    1. Simulating Amplifiers
    2. Prototyping Amplifiers
    3. Testing and Fault-finding
    4. Powering up for the First Time
    5. Power Supplies for Testing
    6. Safety when Working on Equipment
    7. Warning
    8. Safety Regulations
    9. Electrical Safety
      1. Shocks from the Mains Plug
      2. Touch Current
      3. Case Openings
    10. Equipment Temperature and Safety
    11. Touching Hot Parts
    12. Instruction Manuals
  40. Chapter 30 A Brief History of Solid-state Power Amplifiers
    1. First Beginnings: 1953
    2. Transformer-coupled Transistor Power Amplifiers: 1960s
    3. The Lin 6 W Amplifier: 1956
    4. The Tobey & Dinsdale Amplifier: 1961
    5. The Bailey 30 WAmplifier: 1968
    6. Hardcastle & Lane 15 WAmplifier: 1969
    7. The History of VAS Improvements
    8. The History of other Technical Features
    9. Transistors and FETs
    10. Dead Ends of Amplifier Technology 1: Ultrasonic Biasing
    11. Dead Ends of Amplifier Technology 2: Sliding-bias Amplifiers
    12. References
  41. Index
  42. The Signal Transfer Company