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Book Description

Small Signal Audio Design is a highly practical handbook providing an extensive repertoire of circuits that can be assembled to make almost any type of audio system. The publication of Electronics for Vinyl has freed up space for new material, (though this book still contains a lot on moving-magnet and moving-coil electronics) and this fully revised third edition offers wholly new chapters on tape machines, guitar electronics, and variable-gain amplifiers, plus much more. A major theme is the use of inexpensive and readily available parts to obtain state-of-the-art performance for noise, distortion, crosstalk, frequency response accuracy and other parameters. Virtually every page reveals nuggets of specialized knowledge not found anywhere else. For example, you can improve the offness of a fader simply by adding a resistor in the right place- if you know the right place.

Essential points of theory that bear on practical audio performance are lucidly and thoroughly explained, with the mathematics kept to an absolute minimum. Self’s background in design for manufacture ensures he keeps a wary eye on the cost of things.

This book features the engaging prose style familiar to readers of his other books. You will learn why mercury-filled cables are not a good idea, the pitfalls of plating gold on copper, and what quotes from Star Trek have to do with PCB design.

Learn how to:

    • make amplifiers with apparently impossibly low noise
    • design discrete circuitry that can handle enormous signals with vanishingly low distortion
    • use humble low-gain transistors to make an amplifier with an input impedance of more than 50 megohms
    • transform the performance of low-cost-opamps
    • build active filters with very low noise and distortion
    • make incredibly accurate volume controls
    • make a huge variety of audio equalisers
    • make magnetic cartridge preamplifiers that have noise so low it is limited by basic physics, by using load synthesis
    • sum, switch, clip, compress, and route audio signals
    • be confident that phase perception is not an issue

This expanded and updated third edition contains extensive new material on optimising RIAA equalisation, electronics for ribbon microphones, summation of noise sources, defining system frequency response, loudness controls, and much more. Including all the crucial theory, but with minimal mathematics, Small Signal Audio Design is the must-have companion for anyone studying, researching, or working in audio engineering and audio electronics.

Table of Contents

  1. Cover
  2. Half Title
  3. Title
  4. Copyright
  5. Dedication
  6. Contents
  7. Preface
  8. Acknowledgments
  9. Chapter 1 The Basics
    1. Signals
    2. Amplifiers
      1. Voltage Amplifiers
      2. Transconductance Amplifiers
      3. Current Amplifiers
      4. Transimpedance Amplifiers
    3. Negative Feedback
    4. Nominal Signal Levels and Dynamic Range
    5. Frequency Response
      1. Frequency Response: Cascaded Stages
    6. Phase Perception
    7. Gain Structures
      1. Amplification Then Attenuation
      2. Attenuation Then Amplification
      3. Raising the Input Signal to the Nominal Level
      4. Active Gain Controls
    8. Noise
    9. Johnson Noise
    10. Shot Noise
    11. 1/f Noise (Flicker Noise)
    12. Popcorn Noise
    13. Summing Noise Sources
    14. Noise in Amplifiers
    15. Noise in Bipolar Transistors
      1. Bipolar Transistor Voltage Noise
      2. Bipolar Transistor Current Noise
    16. Noise in JFETs
      1. Noise in Opamps
    17. Noise Gain
    18. Low-Noise Opamp Circuitry
    19. Noise Measurements
    20. How to Attenuate Quietly
    21. How to Amplify Quietly
    22. How to Invert Quietly
    23. How to Balance Quietly
    24. Ultra-Low-Noise Design With Multi-Path Amplifiers
      1. Ultra-Low-Noise Voltage Buffers
      2. Ultra-Low-Noise Amplifiers
    25. Multiple Amplifiers for Greater Drive Capability
  10. Chapter 2 Components
    1. Conductors
      1. Copper and Other Conductive Elements
      2. The Metallurgy of Copper
      3. Gold and Its Uses
      4. Cable and Wiring Resistance
      5. PCB Track Resistance
    2. PCB Track-to-Track Crosstalk
    3. The Three-Layer PCB
    4. Impedances and Crosstalk: A Case History
    5. Resistors
      1. Through-Hole Resistors
      2. Surface-Mount Resistors
      3. Resistor Series
      4. Resistor Accuracy: Two-Resistor Combinations
      5. Resistor Accuracy: Three-Resistor Combinations
      6. Other Resistor Combinations
      7. Resistor Value Distributions
      8. The Uniform Distribution
      9. Resistor Imperfections
      10. Resistor Excess Noise
      11. Resistor Non-Linearity
    6. Capacitors
      1. Capacitor Series
      2. Capacitor Non-Linearity Examined
      3. Non-Electrolytic Capacitor Non-Linearity
      4. Electrolytic Capacitor Non-Linearity
    7. Inductors
  11. Chapter 3 Discrete Transistor Circuitry
    1. Why Use Discrete Transistor Circuitry?
    2. Bipolars and FETs
    3. Bipolar Junction Transistors
    4. The Transistor Equation
    5. Beta
    6. Unity-Gain Buffer Stages
      1. The Simple Emitter-Follower
      2. The Constant-Current Emitter-Follower
      3. The Push-Pull Emitter-Follower
      4. Emitter-Follower Stability
      5. CFP Emitter-Followers
      6. Improved Unity-Gain Buffers
    7. Gain Stages
      1. One-Transistor Shunt-Feedback Gain Stages
      2. One-Transistor Series-Feedback Gain Stages
      3. Two-Transistor Shunt-Feedback Gain Stages
      4. Two-Transistor Shunt-Feedback Stages: Improving Linearity
      5. Two-Transistor Shunt-Feedback Stages: Noise
      6. Two-Transistor Shunt-Feedback Stages: Bootstrapping
      7. Two-Transistor Shunt-Feedback Stages as Summing Amplifiers
      8. Two-Transistor Series-Feedback Gain Stages
    8. Discrete Opamp Design
      1. Discrete Opamp Design: The Input Stage
      2. Discrete Opamp Design: The Second Stage
      3. Discrete Opamp Design: The Output Stage
    9. High-Input-Impedance Bipolar Stages
  12. Chapter 4 Opamps and Their Properties
    1. Introduction
    2. A Very Brief History of Opamps
    3. Opamp Properties: Noise
    4. Opamp Properties: Slew Rate
    5. Opamp Properties: Common Mode Range
    6. Opamp Properties: Input Offset Voltage
    7. Opamp Properties: Bias Current
    8. Opamp Properties: Cost
    9. Opamp Properties: Distortion
      1. Opamp Internal Distortion
      2. Slew-Rate Limiting Distortion
      3. Distortion Due to Loading
      4. Thermal Distortion
      5. Common-Mode Distortion
      6. Common-Mode Distortion: Bipolar Input Opamps
      7. Common-Mode Distortion: JFET Opamps
    10. Selecting the Right Opamp
    11. Opamps Surveyed: BJT Input Types
      1. The LM741 Opamp
    12. The NE5532/5534 Opamp
      1. Deconstructing the 5532
      2. The LM4562 Opamp
      3. The AD797 Opamp
      4. The OP27 Opamp
      5. The OP270 Opamp
      6. The OP275 Opamp
    13. Opamps Surveyed: JFET Input Types
      1. The TL072 Opamp
      2. The TL052 Opamp
      3. The OPA2134 Opamp
      4. The OPA604 Opamp
      5. The OPA627 Opamp
  13. Chapter 5 Opamps for Low Voltages
    1. High Fidelity From Low Voltages
    2. Running Opamps From a Single +5 V Supply Rail
    3. Opamps for 5 V Operation
    4. The NE5532 in +5 V Operation
    5. The LM4562 in +5 V Operation
    6. The AD8022 in +5 V Operation
    7. The AD8397 in +5 V Operation
    8. Opamps for 3.3 V Single-Rail Operation
  14. Chapter 6 Filters
    1. Introduction
    2. Passive Filters
    3. Active Filters
    4. Low-Pass Filters
    5. High-Pass Filters
    6. Combined Low-Pass and High-Pass Filters
    7. Band-Pass Filters
    8. Notch Filters
    9. All-Pass Filters
    10. Filter Characteristics
    11. Sallen and Key Low-Pass Filters
    12. Sallen and Key High-Pass Filters
    13. Distortion in Sallen and Key Filters
    14. Multiple-Feedback Band-Pass Filters
    15. Notch Filters
    16. Differential Filters
  15. Chapter 7 Preamplifier Architectures
    1. Passive Preamplifiers
    2. Active Preamplifiers
    3. Amplification and the Gain-Distribution Problem
    4. Active Gain Controls
    5. Active Gain Controls Plus Passive Attenuators
    6. Recording Facilities
    7. Tone Controls
  16. Chapter 8 Variable Gain Stages
    1. Amplifier Stages With Gain From Unity Upwards: Single-Gain Pot
    2. Amplifier Stages With Gain From Unity Upwards: Dual-Gain Pot
    3. Combining Gain Stages With Active Filters
    4. Amplifier Stages With Gain From Zero Upwards: Single-Gain Pot
    5. Amplifier Stages With Gain From Zero Upwards: Dual-Gain Pot
    6. Switched-Gain Amplifiers
  17. Chapter 9 Moving-Magnet Inputs: Levels and RIAA Equalisation
    1. Cartridge Types
    2. The Vinyl Medium
    3. Spurious Signals
    4. Other Vinyl Problems
    5. Maximum Signal Levels From Vinyl
    6. Moving-Magnet Cartridge Sensitivities
    7. Overload Margins and Amplifier Limitations
    8. Equalisation and Its Discontents
    9. The Unloved IEC Amendment
    10. The “Neumann Pole”
    11. MM Amplifier Configurations
    12. Opamp MM Input Stages
    13. Calculating the RIAA Equalisation Components
    14. Implementing RIAA Equalisation
    15. Implementing the IEC Amendment
    16. RIAA Series-Feedback Network Configurations
    17. RIAA Optimisation: C1 as a Single E6 Capacitor, 2xE24
    18. RIAA Optimisation: C1 as 3 x 10 nF Capacitors, 2xE24
    19. RIAA Optimisation: C1 as 4 x 10 nF Capacitors, 2xE24
    20. RIAA Optimisation: The Willmann Tables
    21. RIAA Optimisation: C1 as 3 x 10 nF Capacitors, 3xE24
    22. RIAA Optimisation: C1 as 4 x 10 nF Capacitors, 3xE24
    23. Switched-Gain MM RIAA Amplifiers
    24. Switched-Gain MM/MC RIAA Amplifiers
    25. Open-Loop Gain and RIAA Accuracy
    26. Passive and Semi-Passive RIAA Equalisation
    27. MM Cartridge Loading and Frequency Response
    28. MM Cartridge–Preamplifier Interaction
    29. MM Cartridge DC and AC Coupling
    30. Noise in MM RIAA Preamplifiers
    31. Hybrid MM Amplifiers
    32. Balanced MM Inputs
    33. Noise in Balanced MM Inputs
    34. Noise Weighting
    35. Noise Measurements
    36. Cartridge Load Synthesis for Lower Noise
    37. Subsonic Filters
      1. Subsonic Filtering: Butterworth Filters
      2. Subsonic Filtering: Elliptical Filters
      3. Subsonic Filtering by Cancellation
    38. Ultrasonic Filters
    39. A Practical MM Amplifier #3
  18. Chapter 10 Moving-Coil Head Amplifiers
    1. Moving-Coil Cartridge Characteristics
    2. The Limits on MC Noise Performance
    3. Amplification Strategies
    4. Moving-Coil Transformers
    5. Moving-Coil Input Amplifiers
    6. An Effective MC Amplifier Configuration
    7. The Complete Circuit
    8. Performance
  19. Chapter 11 Tape Replay
    1. The Return of Tape
    2. A Brief History of Tape Recording
    3. The Basics of Tape Recording
    4. Multi-Track Recording
    5. Tape Heads
    6. Tape Replay
    7. Tape Replay Equalisation
    8. Tape Replay Amplifiers
    9. Replay Noise: Calculation
    10. Replay Noise: Measurements
    11. Load Synthesis
    12. Noise Reduction Systems
    13. Dolby HX-Pro
  20. Chapter 12 Guitar Preamplifiers
    1. Electric Guitar Technology
    2. Guitar Pickups
    3. Pickup Characteristics
    4. Guitar Wiring
    5. Guitar Leads
    6. Guitar Preamplifiers
    7. Guitar Preamplifier Noise: Calculations
    8. Guitar Preamplifier Noise: Measurements
    9. Guitar Amplifiers and Guitar Effects
    10. Guitar Direct Injection
  21. Chapter 13 Volume Controls
    1. Volume Controls
    2. Volume Control Laws
    3. Loaded Linear Pots
    4. Dual-Action Volume Controls
    5. Tapped Volume Controls
    6. Slide Faders
    7. Active Volume Controls
    8. The Baxandall Active Volume Control
    9. The Baxandall Volume Control Law
    10. A Practical Baxandall Active Volume Stage
    11. Low-Noise Baxandall Active Volume Stages
    12. The Baxandall Volume Control: Loading Effects
    13. An Improved Baxandall Active Volume Stage With Lower Noise
    14. Baxandall Active Volume Stage Plus Passive Control
    15. The Overlap Penalty
    16. Potentiometers and DC
    17. Belt-Ganged Volume Controls
    18. Motorised Potentiometers
    19. Stepped Volume Controls
    20. Switched Attenuator Volume Controls
    21. Relay-Switched Volume Controls
    22. Transformer-Tap Volume Controls
    23. Integrated Circuit Volume Controls
    24. Loudness Controls
    25. The Newcomb and Young Loudness Control
  22. Chapter 14 Balance Controls
    1. The Ideal Balance Law
    2. Balance Controls: Passive
    3. Balance Controls: Active
    4. Combining Balance Controls With Other Stages
    5. Switched Balance Controls
    6. Mono-Stereo Switches
    7. Width Controls
  23. Chapter 15 Tone Controls and Equalisers
    1. Introduction
    2. Passive Tone Controls
    3. Baxandall Tone Controls
      1. The Baxandall One-LF-Capacitor Tone Control
      2. The Baxandall Two-LF-Capacitor Tone Control
      3. The Baxandall Two-HF-Capacitor Tone Control
      4. The Baxandall Tone Control: Impedance and Noise
      5. Combining a Baxandall Stage With an Active Balance Control
      6. Switched-HF-Frequency Baxandall Controls
    4. Variable-Frequency HF EQ
    5. Variable-Frequency LF EQ
    6. A New Type of Switched-Frequency LF EQ
    7. Variable-Frequency HF and LF EQ in One Stage
    8. Tilt or Tone-Balance Controls
    9. Middle Controls
      1. Fixed Frequency Baxandall Middle Controls
      2. Three-Band Baxandall EQ in One Stage
      3. Wien Fixed Middle EQ
      4. Wien Fixed Middle EQ: Altering the Q
      5. Variable-Frequency Middle EQ
      6. Single-Gang Variable-Frequency Middle EQ
      7. Switched-Q Variable-Frequency Wien Middle EQ
    10. Switchable Peak/Shelving LF/HF EQ
    11. Parametric Middle EQ
    12. Graphic Equalisers
  24. Chapter 16 Mixer Architecture
    1. Introduction
    2. Performance Factors
    3. Mixer Internal Levels
    4. Mixer Architecture
    5. The Split Mixing Architecture
    6. The In-Line Mixing Architecture
    7. A Closer Look at Split-Format Modules
      1. The Channel Module (Split Format)
      2. Effect Return Modules
      3. The Group Module
      4. The Master Module
      5. Talkback and Oscillator Systems
    8. The In-Line Channel Module
  25. Chapter 17 Microphone Preamplifiers
    1. Microphone Types
    2. Microphone Preamplifier Requirements
    3. Transformer Microphone Inputs
    4. The Simple Hybrid Microphone Preamplifier
    5. The Balanced-Feedback Hybrid Microphone Preamplifier (BFMA)
    6. Microphone and Line Input Pads
    7. The Padless Microphone Preamplifier
    8. Capacitor Microphone Head Amplifiers
    9. Ribbon Microphone Amplifiers
  26. Chapter 18 Line Inputs
    1. External Signal Levels
    2. Internal Signal Levels
    3. Input Amplifier Functions
    4. Unbalanced Inputs
    5. Balanced Interconnections
    6. The Advantages of Balanced Interconnections
    7. The Disadvantages of Balanced Interconnections
    8. Balanced Cables and Interference
    9. Balanced Connectors
    10. Balanced Signal Levels
    11. Electronic Versus Transformer Balanced Inputs
    12. Common Mode Rejection
      1. The Basic Electronic Balanced Input
      2. The Basic Balanced Input and Opamp Effects
    13. Opamp Frequency Response Effects
    14. Opamp CMRR Effects
    15. Amplifier Component Mismatch Effects
    16. A Practical Balanced Input
    17. Variations on the Balanced Input Stage
      1. Combined Unbalanced and Balanced Inputs
      2. The Superbal Input
      3. Switched-Gain Balanced Inputs
      4. Variable-Gain Balanced Inputs
      5. Combined Line Input and Balance Control Stage With Low Noise
      6. The Self Variable-Gain Line Input
      7. High Input-Impedance Balanced Inputs
      8. The Inverting Two-Opamp Input
      9. The Instrumentation Amplifier
      10. Instrumentation Amplifier Applications
      11. The Instrumentation Amplifier With 4x Gain
      12. The Instrumentation Amplifier at Unity Gain
      13. The Instrumentation Amplifier and Gain Controls
      14. The Instrumentation Amplifier and the Whitlock Bootstrap
    18. Transformer Balanced Inputs
    19. Input Overvoltage Protection
    20. Low-Noise Balanced Inputs
    21. Low-Noise Balanced Inputs in Action
    22. Ultra-Low-Noise Balanced Inputs
  27. Chapter 19 Line Outputs
    1. Unbalanced Outputs
    2. Zero-Impedance Outputs
    3. Ground-Cancelling Outputs: Basics
    4. Ground-Cancelling Outputs: Zero-Impedance Output
    5. Ground-Cancelling Outputs: CMRR
    6. Ground-Cancelling Outputs: Send Amplifier Noise
    7. Ground-Cancelling Outputs: Into a Balanced Input
    8. Ground-Cancelling Outputs: History
    9. Balanced Outputs: Basics
    10. Balanced Outputs: Output Impedance
    11. Balanced Outputs: Noise
    12. Quasi-Floating Outputs
    13. Transformer Balanced Outputs
    14. Output Transformer Frequency Response
    15. Output Transformer Distortion
    16. Reducing Output Transformer Distortion
  28. Chapter 20 Headphone Amplifiers
    1. Driving Heavy Loads
    2. Driving Headphones
    3. Special Opamps
    4. Multiple Opamps
    5. Opamp-Transistor Hybrid Amplifiers
    6. Discrete Class-AB Headphone Amplifiers
    7. Discrete Class-A Headphone Amplifiers
      1. Gain
      2. Maximum Output
      3. Noise Performance
      4. Power Consumption
    8. Balanced Headphone Amplifiers
  29. Chapter 21 Signal Switching
    1. Mechanical Switches
    2. Input-Select Switching: Mechanical
    3. The Virtual Contact: Mechanical
    4. Relay Switching
    5. Electronic Switching
    6. Switching with CMOS Analogue Gates
      1. CMOS Gates in Voltage Mode
      2. CMOS Gates in Current Mode
      3. CMOS Series-Shunt Current Mode
      4. Control Voltage Feedthrough in CMOS Gates
      5. CMOS Gates at Higher Voltages
      6. CMOS Gates at Low Voltages
      7. CMOS Gate Costs
    7. Discrete JFET Switching
      1. The Series JFET Switch in Voltage Mode
      2. The Shunt JFET Switch in Voltage Mode
      3. JFETs in Current Mode
      4. Reducing Distortion by Biasing
      5. JFET Drive Circuitry
      6. Physical Layout and Offness
      7. Dealing With the DC Conditions
      8. A Soft Changeover Circuit
      9. Control Voltage Feedthrough in JFETS
  30. Chapter 22 Mixer Sub-Systems
    1. Mixer Bus Systems
    2. Input Arrangements
    3. Equalisation
    4. Insert Points
    5. How to Move a Circuit Block
    6. Faders
      1. Improving Fader Offness
    7. Post-Fade Amplifiers
    8. Direct Outputs
    9. Panpots
      1. Passive Panpots
      2. The Active Panpot
      3. LCR Panpots
    10. Routing Systems
    11. Auxiliary Sends
    12. Group Module Circuit Blocks
    13. Summing Systems: Voltage Summing
    14. Summing Systems: Virtual-Earth Summing
    15. Balanced Summing Systems
    16. Ground-Cancelling Summing Systems
    17. Distributed Summing Systems
    18. Summing Amplifiers
    19. Hybrid Summing Amplifiers
    20. Balanced Hybrid Summing Amplifiers
    21. Balancing Tracks to Reduce Crosstalk
    22. The Multi-Function Summing Amplifier
    23. PFL Systems
      1. PFL Summing
      2. PFL Switching
      3. PFL Detection
      4. Virtual-Earth PFL Detection
    24. AFL Systems
    25. Solo-in-Place Systems
    26. Talkback Microphone Amplifiers
    27. Line-Up Oscillators
    28. The Flash Bus
    29. Power Supply Protection
    30. Console Cooling and Component Lifetimes
  31. Chapter 23 Level Indication and Metering
    1. Signal-Present Indication
    2. Peak Indication
    3. The Log Law Level LED (LLLL)
    4. Distributed Peak Detection
    5. Combined LED Indicators
    6. VU Meters
    7. PPMs
    8. LED Bar-Graph Metering
    9. A More Efficient LED Bar-Graph Architecture
    10. Vacuum Fluorescent Displays
    11. Plasma Displays
    12. Liquid Crystal Displays
  32. Chapter 24 Level Control and Special Circuits
    1. Gain-Control Elements
      1. A Brief History of Gain-Control Elements
      2. JFETs
      3. Operational Transconductance Amplifiers (OTAs)
      4. Voltage-Controlled Amplifiers (VCAs)
    2. Compressors and Limiters
      1. Attack Artefacts
      2. Decay Artefacts
      3. Subtractive VCA Control
    3. Noise Gates
    4. Clipping
      1. Diode Clipping
      2. Active Clipping With Transistors
      3. Active Clipping With Opamps
    5. 1. Clipping by Clamping
    6. 2. Negative-Feedback Clipping
    7. 3. Feedforward Clipping
    8. Noise Generators
    9. Pinkening Filters
  33. Chapter 25 Power Supplies
    1. Opamp Supply Rail Voltages
    2. Designing a ±15 V Supply
    3. Designing a ±17 V Supply
    4. Using Variable-Voltage Regulators
    5. Improving Ripple Performance
    6. Dual Supplies From a Single Winding
    7. Power Supplies for Discrete Circuitry
    8. Larger Power Supplies
    9. Mutual Shutdown Circuitry
    10. Very Large Power Supplies
    11. Microcontroller and Relay Supplies
    12. +48 V Phantom Power Supplies
  34. Chapter 26 Interfacing With the Digital Domain
    1. PCB Layout Considerations
    2. Nominal Levels and ADCs
    3. Some Typical ADCs
    4. Interfacing With ADC Inputs
    5. Some Typical DACs
    6. Interfacing With DAC Outputs
    7. Interfacing With Microcontrollers
  35. Appendix
  36. Index
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