Theoretical Analysis and Design of Analog Distortion Circuitry
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Rochester Institute of Technology RIT Scholar Works Theses 5-2020 Theoretical Analysis and Design of Analog Distortion Circuitry Daniel Saber [email protected] Follow this and additional works at: https://scholarworks.rit.edu/theses Recommended Citation Saber, Daniel, "Theoretical Analysis and Design of Analog Distortion Circuitry" (2020). Thesis. Rochester Institute of Technology. Accessed from This Master's Project is brought to you for free and open access by RIT Scholar Works. It has been accepted for inclusion in Theses by an authorized administrator of RIT Scholar Works. For more information, please contact [email protected]. THEORETICAL ANALYSIS AND DESIGN OF ANALOG DISTORTION CIRCUITRY by DANIEL SABER GRADUATE PAPER Submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE in Electrical Engineering Approved by: Mr. Mark A. Indovina, Senior Lecturer Graduate Research Advisor, Department of Electrical and Microelectronic Engineering Dr. Sohail A. Dianat, Professor Department Head, Department of Electrical and Microelectronic Engineering DEPARTMENT OF ELECTRICAL AND MICROELECTRONIC ENGINEERING KATE GLEASON COLLEGE OF ENGINEERING ROCHESTER INSTITUTE OF TECHNOLOGY ROCHESTER,NEW YORK MAY, 2020 I dedicate this work to my father Dr. Eli Saber, my mother Debra Saber, and my brothers Paul and Joseph Saber. Declaration I hereby declare that except where specific reference is made to the work of others, that all content of this Graduate Paper are original and have not been submitted in whole or in part for consideration for any other degree or qualification in this, or any other University. This Graduate Project is the result of my own work and includes nothing which is the outcome of work done in collaboration, except where specifically indicated in the text. Daniel Saber May, 2020 Acknowledgements I would like to take this opportunity to thank my family. Thank you Paul, Joe, Mom, and Dad for your continual support throughout my college career. I would also like to thank my friends for their support as well; the friendships I have made with some of my colleagues have been invaluable to my success. Lastly, I would like to thank Professor Mark Indovina for offering me advice, guidance, and setting me up to be successful in my research. Abstract The music industry is one that demands the use of modern engineering technologies, such as ef- fects pedals, in order to achieve a customizable tone for a unique style. Using effects pedals such as distortion, delay, reverb, and many more, a musician can create a specific tone with distinct characteristics and adjust certain parameters of the sound to their own preference. This paper will focus on distortion pedals and the theory revolving around the design of a custom distortion pedal. Different kinds of distortion require different circuitry and different components. Certain types of guitar distortion pedals create distortion using simple transistor circuits and/or diode clipping. Others employ the use of operational amplifiers paired with diodes to create a“dis- torted” sound. Different musicians may demand various kinds of distortion, and certain types of distortion are used for different styles. For example, fuzz is a type of distortion which is very ‘messy’ in quality, but widely used for funk, blues, and rock music. There are two main clas- sifications of distortion: overdrive (soft clipping), and regular distortion (hard clipping). Within these two categories, many different types of distortion can be produced. Using specific circuitry is imperative to attaining a specific tonality. By investigating and experimenting with different designs, this research paper attempts to explain and justify the theory behind the creation of distortion in a guitar pedal. Contents Contents v List of Figures viii 1 Introduction1 1.0.1 Research Goals . .2 1.0.2 Contributions . .3 1.0.3 Organization . .3 2 Related Work5 2.1 Introduction . .5 2.2 A Brief History of the Electric Guitar . .6 2.3 The Electric Guitar: Elementary Concepts . .7 2.3.1 Magnetic Guitar Pickups . .7 2.3.2 Guitar Amplifiers: Valve vs Solid State . 10 2.3.3 Guitar Effects Pedals: Analog and Digital Models . 12 2.3.4 Creating Distortion and Overdrive . 13 3 Architecture and Implementation of Design 16 3.1 Block Diagram Overview . 16 Contents vi 3.1.1 Top Level Block Diagram . 16 3.2 Power Block . 17 3.3 Buffer Stage . 18 3.4 Gain Stage . 20 3.5 Hard Clipping Stage . 20 3.6 Tone Control Stage . 23 4 Theoretical Analysis and Design 25 4.1 Fundamental Theoretical Concepts . 25 4.1.1 Operational Amplifiers . 25 4.1.2 Diodes and Clipping Circuits . 27 4.2 Theoretical Design and Simulation . 31 4.2.1 Buffer Circuit Design . 31 4.2.2 Gain Stage . 33 4.2.3 Hard Clipping Stage . 40 4.2.4 Tone Control Stage . 44 4.3 Complete Analog Circuit: Final Theoretical Simulations . 47 4.3.1 Simulation and Validation . 47 5 Hardware Analysis and Testing 52 5.1 Final Hardware Schematic and PCB Layout . 52 5.2 Hardware Testing and Validation . 55 5.2.1 Validation: Buffer Circuit . 55 5.2.2 Validation: Gain Stage with Hard Clipping . 57 5.2.3 Validation: Tone Control Stage . 61 5.2.4 Validation: Complete Circuit . 62 Contents vii 5.3 Modeling of Diodes . 62 5.3.1 Diode Hard Clipping Profiles . 62 5.3.2 Diode Soft Clipping Profiles . 71 6 Conclusions 76 6.1 Summary of Results . 76 6.2 Outlook and Future Work . 77 References 78 I Appendix I-1 I.1 Ibanez Tube Screamer . I-2 I.2 BOSS DS-1 . I-3 I.3 Pedal Enclosure . I-4 List of Figures 2.1 Single Coil Guitar Pickup [1]............................7 2.2 Magnetic Field as a Function of Vertical Displacement [2]............9 2.3 Changing Magnetic Field Due to Vibrating Wire [2]................9 2.4 Valve vs Solid State Frequency Response [3]................... 11 2.5 Different Types of Clipping by Guitar Amplifiers [4]............... 12 2.6 Boss DS-1 Block Diagram [5]........................... 15 2.7 General Diode Clipping Circuit [5]......................... 15 3.1 Top Level Block Diagram . 17 3.2 Power Block . 18 3.3 Buffer Circuit . 19 3.4 Non-inverting Amplifier: Gain Stage . 21 3.5 Hard Clipping Stage . 22 3.6 Tone Control Stage . 24 4.1 Ideal Operational Amplifier [6]........................... 27 4.2 Non-inverting Configuration [6].......................... 28 4.3 Diode IV Curve [6]................................. 29 4.4 General Diode Clipping Circuit . 31 List of Figures ix 4.5 Buffer Circuit Theoretical Design . 33 4.6 DC Voltages . 34 4.7 Buffer: Theoretical Simulation . 34 4.8 Theoretical Schematic: Gain Stage . 35 4.9 Minimum Gain Setting: Potentiometer = 1MW ................... 37 4.10 Potentiometer = 250kW ............................... 37 4.11 Potentiometer = 10kW ................................ 38 4.12 Maximum Gain Setting: Potentiometer = 100 W .................. 38 4.13 Gain Stage: Frequency Response . 39 4.14 Gain Stage with Hard Clipping Stage . 40 4.15 Volume Test: Load Resistor = 10W ......................... 41 4.16 Volume Test: Load Resistor = 1kW ......................... 41 4.17 Volume Test: Load Resistor = 100kW ....................... 41 4.18 Clipping Test: Gain Resistor = 250kW ....................... 42 4.19 Clipping Test: Gain Resistor = 6.2kW ....................... 43 4.20 Clipping Test: Gain Resistor = 100 W ....................... 43 4.21 Tone Control Theoretical Schematic . 45 4.22 Tone Control Frequency Response . 45 4.23 Tone Control: DC Voltages . 46 4.24 Tone Control: Transient Simulation . 46 4.25 Complete Theoretical Schematic . 47 4.26 Transient 1: Gain potentiometer = 1MW ...................... 48 4.27 Transient 2: Gain potentiometer = 20kW ...................... 49 4.28 Transient 3: Gain potentiometer = 8kW ...................... 49 4.29 Frequency Response: Gain potentiometer = 1MW ................. 50 List of Figures x 4.30 Frequency Response: Gain potentiometer = 100kW ................ 50 4.31 Frequency Response: Gain potentiometer = 10kW ................ 51 5.1 Final Altium Schematic . 54 5.2 Final PCB Layout . 56 5.3 Hardware Buffer Simulation . 57 5.4 Hardware Gain Simulation: 1MW Potentiometer . 58 5.5 Hardware Gain Simulation: 10kW Potentiometer . 59 5.6 Hardware Gain Simulation: 4.7kW Potentiometer . 60 5.7 Hardware Tone Control Simulation . 61 5.8 Hardware Gain Simulation: 1MW Potentiometer . 63 5.9 Hardware Gain Simulation: 10kW Potentiometer . 64 5.10 Hardware Gain Simulation: 4.7kW Potentiometer . 65 5.11 Simulation of 1N4735 Diode . 67 5.12 Simulation of 1N4148 Diode . 68 5.13 Simulation of 1N914 Diode . 69 5.14 Simulation of 1N4004 Diode . 70 5.15 Simulation of Red LED . 71 5.16 Simulation of 1N914 Diode . 73 5.17 Simulation of 1N4004 . 74 5.18 Simulation of Red LED . 75 I.1 Ibanez Guitar Pedal . I-2 I.2 BOSS Guitar Pedal . I-3 I.3 Enclosure for Custom Analog pedal . I-4 Chapter 1 Introduction Guitar pedal technology has been extremely prevalent in the rock and roll scene since its in- ception in 1948. Different guitar virtuosos have achieved their signature tone through the use of very specific rigs, using specific pedals, which create a one-of-a-kind sound. Guitarists such Jimi Hendrix, Kirk Hammett, and Zakk Wylde are widely known for using wah pedals in their playing to create their signature tones. Randy Rhoads is known for using chorus pedals on his shred solos, and his high distorted tone is sought after by many. Using guitar pedals, musicians can invent and create different sounds for different styles, and build a brand based on said style. There are many different kinds of effects that a musician can employ into their rig to create a unique sound. Such effects include delay, reverb, distortion, phasors, and many more. There are many ways to design.