Electronics for Guitarists

This updated, augmented third edition is aimed at hobbyists, students, engineers, and others who would like to learn more about the design and operation of electronic circuits used by guitarists. This book presents accessible qualitative and quantitative descriptions and analysis of a wide range of popular amplifier and effects circuits, along with basic design techniques allowing the reader to design their own circuits. The new edition further includes several additional circuits and topics suggested by readers of the previous editions, including noise gates, analog multipliers, the effects loop, and additional tube amplifier design examples. Extends amp analysis and design, adds effects loop in amp design, and clarifies the effect-circuit operation; Adds additional vacuum tube amp design examples and extracting parameters from tube characteristic curves; Includes new coverage of the operation and design of noise gate circuits Preface Who This Book Is Written For Analog Rules! About the Math Building the Circuits Vacuum Tubes The Third Edition Safety Disclaimer Acknowledgments Contact Information Internet Links and Descriptions Used in Text Contents List of Figures Chapter 1: Power Supplies Introduction A Simple Power Supply Circuit The Transformer The Rectifier Analysis of the Rectifier The Frequency Domain The Filter Ripple Voltage Filter Analysis: The Frequency Domain Response Curves, Decades, and Octaves Power Indicators Neon Lamps Light-Emitting Diodes LED Current Limiting Resistor Calculation Incandescent Lamps A Basic Regulated Power Supply The 78xx Voltage Regulator Dropout Voltage Power Dissipation Bipolar Power Supplies Using Batteries for Bipolar Power A Typical Bipolar Power Supply A Regulated Bipolar Power Supply Two-Diode, Full-Wave Rectifier Basic Vacuum Tube Diode Power Supplies Vacuum Tube Diodes Reverse Bias Forward Bias The 5AR4, 5U4-GB, and 5Y3-GT Diodes Typical Vacuum Tube Diode Power Supplies The LC, Pi Filter RC Pi Filter Supply Voltage Distribution Final Comments Summary of Equations Chapter 2: Pickups and Volume and Tone Controls Introduction Single-Coil Magnetic Pickups Humbucker Pickups Peak and Average Output Voltages More Magnetic Pickup Analysis Inductance A Pickup Winding Example Winding Resistance Winding Capacitance Approximate Circuit Model for a Magnetic Pickup Piezoelectric Pickups Piezoelectric Pickup Analysis Example of Calculation: Input Resistance and Corner Frequency Guitar Volume and Tone Control Circuits Potentiometers Potentiometer Taper The Transfer Function Rheostats Basic Guitar Tone Control Operation Damping Multiple Pickups Pickup Phasing Amplifier Tone Control Circuits A Basic Tone Control Circuit Improved Single-Pot Tone Control Baxandall Tone Control Other Tone Control Circuits Final Comments Summary of Equations Chapter 3: Small-Signal and Low-Power Amplifiers Introduction Gain Decibels Other Amplifier Parameters Distortion Input Resistance Output Resistance Bandwidth Slew Rate Amplifier Classifications and Biasing Bipolar Junction Transistors The Active Region Saturation Cutoff Biasing Class A Class B Class AB The Load Line Clipping DC and AC Load Lines Class A Power Dissipation Characteristics The Common Emitter Configuration The Emitter Follower (Common Collector) Configuration The Common Base Configuration Field Effect Transistors Bipolar Transistor Specifications Basic BJT Amplifier Operation Voltage Divider Biased CE Amplifier DC Q-Point Analysis Equations for Fig. 3.13 Beta Independence AC Analysis Equations for Fig. 3.13 Common Emitter Amplifier Analysis Example DC Q-Point Analysis AC Analysis Experimental Results Some Practical Testing and Measurement Tips Amplifying a Guitar Signal Frequency Response Negative Feedback Local and Global Feedback A JFET Common Source, Class A Amplifier JFET Parameters JFET Amplifier Overview JFET Centered Q-Point BJT vs. JFET Piezoelectric Pickup Preamplifier Phone Jack Power Switching Increasing Voltage Gain A JFET-BJT Multiple-Stage Amplifier Some Useful Modifications A Closer Look at Transconductance BJT, JFET, and MOSFET Transconductance Equations A MOSFET Common Source Amplifier Theoretical Analysis Experimental Results Operational Amplifiers Basic Noninverting and Inverting Op Amp Equations Noninverting and Inverting Amplifier Analysis Power Bandwidth Single-Polarity Supply Operation Noninverting Amplifier The Two Golden Rules of Op Amp Analysis Inverting Amplifier Parasitic Oscillation Inside the Op Amp Operational Transconductance Amplifiers An OTA Analysis Example The OTA as a Voltage-Controlled Amplifier Current Difference Amplifiers Your Turn Miscellaneous Useful Circuits An Audio Test Oscillator A Closer Look at the Oscillator Output Signal The Rail Splitter High-Power Rail Splitter Use with Pedal Boards and Daisy Chain Power Cords Charge Pumps Charge Pump vs. Rail Splitter Class A, Collector Feedback, Germanium Transistor Amplifier DC Analysis AC Analysis Experimental Results Practical Use of the Amplifier An Alternate JFET Input Version Mixing Magnetic and Piezo Pickups Final Comments Summary of Equations Chapter 4: Solid-State Power Amplifiers Introduction The Basic Push-Pull Stage Class AB: Eliminating Crossover Distortion Output Power Determination Bipolar Power Supply Operation Power Transistors Composite Transistors Darlington Transistors Sziklai Transistors A Complete Power Amplifier Output Stage Analysis Transistor Thermal Analysis Parallel-Connected Power Transistors Thermal Runaway Push-Pull Stage with Parallel Transistors Adding a Tone Control Amplifier Stability Issues Ground Reference Star Grounding Motorboating Decoupling Capacitors The Zobel Network MOSFET Output Stages The VBE Multiplier The Rail Splitter Revisited Enclosing Base-Emitter Junction in the Feedback Loop Converting the Rail Splitter to an Amplifier Slew Rate-Induced Crossover Distortion Final Comments Summary of Equations Chapter 5: Effects Circuits Introduction Signals and Spectra Time, Period, Frequency, and Pitch Sinusoids in the Time Domain Waveform Shape, Symmetry, and Harmonic Relationships Transfer Function Symmetry and Harmonic Distortion An Odd Symmetry Example An Even Symmetry Example An Example of Neither Even Nor Odd Symmetry Intermodulation Distortion Influence of Amplifier Design on Distortion Effects of Negative Feedback Single-Ended vs. Push-Pull Effects of Device Transfer Characteristics on Distortion BJTs FETs Triodes Effect Bypassing Overdrive Circuits Single-Stage Transistor Overdrives Simple BJT Overdrive Sziklai Overdrive Circuit Darlington Overdrive Circuit Multiple-Stage Overdrive Circuits JFET/BJT Overdrive MOSFET/PNP Germanium Overdrive An Op Amp Overdrive Circuit Distortion Circuits Fuzz vs. Distortion Diode Clippers Asymmetrical Clipper with Power Indicator Adjustable Op Amp Distortion Circuit Logarithmic Amplifiers Log Amp Output Equation Derivation Log Amp Distortion Circuit Phase Shifters The All-Pass Filter Optocouplers An Experimental Phase Shifter Circuit Flangers Flanging vs. Phase-Shifting Bucket-Brigade Devices Clock and LFO Generation A BBD-Based Flanger Sampling Frequency and Aliasing Anti-aliasing and Reconstruction Filters Oversampling Chorus Effect Envelope Followers Signal Envelope Precision Rectifier Circuits Precision Half-Wave Rectifiers Precision Full-Wave Rectifier An Experimental Envelope Follower String Frequency-to-Pulse Converter Compression, Sustain, and Dynamic Range Voltage-Controlled Amplifiers Experimental OTA-Based Compressor Experimental LDR-Based Compression/Sustain Tremolo Reverberation Delay Time Decay Time Reverb Springs A Digital Reverb Modulation and Pitch Shifting Amplitude Modulation Balanced (Ring) Modulation An Experimental Ring Modulator Frequency Doubling A Deeper Dive Analog Multipliers Vocoders Wah-Wah Circuits IGMF Bandpass Filter An IGMF Design Example Varying fo of the IGMF Experimental IGMF Wah-Wah Circuits Eliminating Switching Pop A Gyrator-Based Wah-Wah Circuit Envelope-Controlled Filter (Auto-Wah) Noise Gates A Little Deeper Look at the LM358 Sampling, Quantization, DACs, and ADCs The R-2R Ladder DAC Operation Effect on an Audio Signal Final Comments Summary of Equations Chapter 6: Low-Power Vacuum Tube Amplifiers Introduction Commonly Used Vacuum Tubes Parts Sources and Availability Vacuum Tube Parameters and Data Sheets Absolute Maximum Ratings Other Data Sheet Parameters Tube Pin Numbering General Amplifier Design Principles Cathode Feedback Biasing Fixed Biasing Class A, Resistance-Coupled, Common Cathode Amps 12AU7 Low-Power Amp Design Example Alternative Determination of Cathode Resistance RK DC and AC Load Lines Amplifier AC Performance Output Voltage Compliance Experimental Test Results Q-Point Location and Distortion 6AN8 Triode, Low-Power Amp Design Example Amplifier AC Performance The AC Load Line Output Voltage Compliance 12AX7 Low-Power Amp Design Example Amplifier AC Performance The AC Load Line Output Voltage Compliance Experimental Results 12AT7 Low-Power Amp Design Example Amplifier AC Performance Output Voltage Compliance Pentodes Screen Grid (G2) Suppressor Grid (G3) 6AN8 Pentode, Low-Power Amp Design Example Amplifier AC Performance Output Voltage Compliance Cathode Followers and Phase Splitters Cathodyne Phase Splitter Design Cathode Resistor Determination AC Characteristics A Cathodyne Variation Differential Pair Phase Splitter A Practical Differential Phase Splitter Transformer-Coupled Phase Splitter Determination of Tube Parameters: gm, rP, and μ Basic Definitions of gm, rP, and μ Determination of Triode-Mode Transconductance Determination of Triode-Mode Mu Determination of Triode Dynamic Plate Resistance Final Comments Summary of Equations Chapter 7: Vacuum Tube Power Amplifiers Introduction Maximum Power Transfer Basic Transformer Operation Reflected Load Resistance Magnetic Saturation Transformer Coupling Advantages and Disadvantages A Sampling of Audio Output Transformers Class A, Single-Ended Amplifiers 6L6GC Triode-Mode, SE Amplifier Design Example Choosing an Output Tube Choosing Power Supply Voltage Choosing Quiescent Plate Current IPQ Output Transformer Selection The DC Load Line Two Useful Approximations The AC Load Line Q-Point Voltage Limits AC Characteristics of the Amplifier Grid Resistors and the Gamma Network Substituting an EL34 Q-Point Analysis 6L6GC Pentode-Mode, SE Amplifier Design Example Choosing Power Supply Voltage Choosing Quiescent Plate Current IPQ Output Transformer Selection The AC Load Line Q-Point Voltage Limits AC Characteristics of the Amplifier Grid Resistor and Gamma Network The Screen Grid Resistor, R3 EL84 Pentode-Mode, SE Amplifier Design Example Choosing Power Supply Voltage Q-Point Selection Output Transformer and R′L Selection Determine Cathode Resistance R4 The AC Load Line Q-Point Voltage Limits AC Characteristics of the Amplifier Grid Resistor and Gamma Network The Screen Grid Resistor EL34 Pentode-Mode, SE Amplifier Design Example Plot Q-Point Determine Cathode Resistance RK Select Output Transformer Plot AC Load Line Q-Point Voltage Compliance AC Characteristics of the Amplifier Grid Resistors and Gamma Network Selectable Triode/Pentode Operation Switching RK and Suppressor Grid G2 Switching Only G2 Parallel-Connected Tubes Complete SE Amplifier Examples 6AQ5 Low-Power, SE Practice Amp Amplifier Analysis The Power Supply Efficiency The Finished Amplifier 6L6/EL34 Dual-Mode, SE Amplifier The Power Supply Eliminating the Choke Amplifier Performance Adding A Spring Reverb The Reverb Tank Reverb Design Considerations EL84, 4 Watt, SE Amplifier Adding a Reverb The Power Supply Class A, Single-Ended Amp Distortion Push-Pull Amplifiers Basic DC Operation Basic AC Operation AC Analysis of the Push-Pull Output Transformer Push-Pull Class A Distortion EL34 Triode-Mode, Push-Pull Design Example Q-Point Location and Determination of RK Output Transformer Selection The AC Load Line AC Characteristics of the Amplifier The Cathode Bypass Capacitor A Complete EL34 Triode-Mode Amplifier 6L6GC Pentode-Mode, Push-Pull Design Example Q-Point Location and Determination of RK Output Transformer Selection The AC Load Line AC Characteristics of the Amplifier A Complete 6L6GC Amplifier Standby Operation 6V6 Amplifier with Effects Loop The Effects Loop Low-Power Sections The Output Stage The Power Supply Ultralinear Amplifiers Construction Techniques and Tips Chassis Materials Wiring Tips Testing Tips Build and Test the Amp in Stages Never Operate the Amp Without a Load Final Comments Summary of Equations Appendices Appendix A: Some Basic Circuit Theory Voltage and Current Polarities and Conventions Linear Circuits Series Circuits Ohm ́s Law Kirchhoff ́s Voltage Law Parallel Circuits Nodes Branches Kirchhoff ́s Current Law The Superposition Principle Capacitors, Inductors, and Complex Numbers Transient Behavior Steady-State Behavior Summary of Useful Formulas Ohm ́s Law n Series Resistances n Parallel Resistances Frequency and Period Charging and Discharging Capacitor Inductive and Capacitive Reactance Bipolar Transistor Relationships Triode Relationships JFET Relationships Appendix B: Selected Tube Characteristic Curves Appendix C: Basic Vacuum Tube Operating Principles Diodes Reverse Bias Forward Bias Triodes Amplification Factor Transconductance Dynamic Plate Resistance Tetrodes Pentodes Index This book covers the operation and design of guitar-related electronics circuits. Starting with simple power supply circuits, the book then covers basic transistor amplifiers and op amps, then effects circuits including flangers, phasers, filters and so on. The last chapter covers tube amplifier design. Several practical design examples are presented, as well as complete tube amps of various power output. Details of how to add a spring reverb are also covered here. This is a pretty technical book, but still very interesting. It really helps to demystify the operation of some pretty complex circuits. The math behind all of thet circuits is presented, but you can skip it and just build the circuits to experiment with, or read the circuit descriptions to get a better feel for how effects and amps work.