Small Signal Audio Design

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:
Chapter 1: The Basics Signals Amplifiers Voltage amplifiers Transconductance amplifiers Current amplifiers Transimpedance amplifiers Negative feedback Nominal signal levels and dynamic range Frequency response Frequency response: cascaded stages Phase perception Gain structures Amplification then attenuation Attenuation then amplification Raising the input signal to the nominal level Active-gain-controls Noise Johnson noise Shot noise 1/f noise (flicker noise) Popcorn noise Summing noise sources Noise in amplifiers Noise in bipolar transistors Bipolar transistor voltage noise Bipolar transistor current voltage Noise in JFETs Noise in opamps Noise gain Low-noise opamp circuitry Noise measurements How to attenuate quietly How to amplify quietly How to invert quietly How to balance quietly Ultra low-noise design with multipath amplifiers Ultra low-noise voltage buffers Ultra low-noise amplifiers Multiple amplifiers for greater drive capability Chapter 2: Components Conductors Copper and other conductive elements The metallurgy of copper Gold and its uses Cable and wiring resistance PCB track resistance PCB track-to-track crosstalk The 3-layer PCB Impedances and crosstalk: a case history Resistors Through-hole resistors Surface-mount resistors Resistor series Resistor accuracy: two resistor combinations Resistor accuracy: three resistor combinations Other resistor combinations Resistor value distributions The uniform distribution Resistor imperfections Resistor excess noise Resistor non-linearity Capacitors Capacitor series Capacitor non-linearity examined Non-electrolytic capacitor non-linearity Electrolytic capacitor non-linearity Inductors Chapter 3: Discrete transistor circuitry Why use discrete transistor circuitry? Bipolars and FETs Bipolar junction transistors The transistor equation Beta Unity-gain buffer stages The simple emitter-follower The constant-current emitter-follower The push-pull emitter-follower Emitter-follower stability CFP emitter-followers Improved unity-gain buffers Gain stages One-transistor shunt-feedback gain stages One-transistor series-feedback gain stages Two-transistor shunt-feedback gain stages Two-transistor shunt-feedback stages: improving linearity Two-transistor shunt-feedback stages: noise Two-transistor shunt-feedback stages: bootstrapping Two-transistor shunt-feedback stages as summing amplifiers Two-transistor series-feedback gain stages Discrete opamp design Discrete opamp design: the input stage Discrete opamp design: the second stage Discrete opamp design: the output stage High input impedance bipolar stages Chapter 4: Opamps and their properties Introduction A Very Brief History of Opamps. Opamp properties: noise Opamp properties: slew rate Opamp properties: common mode range Opamp properties: input offset voltage Opamp properties: bias current Opamp properties: cost Opamp properties: distortion Opamp internal distortion Slew-rate limiting distortion Distortion due to loading Thermal distortion Common-mode distortion Common-mode distortion: Bipolar input opamps Common-mode distortion: JFET opamps Selecting The Right Opamp Opamps surveyed: BJT input types The LM741 opamp The NE5532/5534 opamp Deconstructing the 5532 The LM4562 opamp The AD797 opamp The OP27 opamp The OP270 opamp The OP275 opamp Opamps surveyed: JFET input types The TL072 opamp The TL052 opamp The OPA2134 opamp The OPA604 opamp The OPA627 opamp Chapter 5: Opamps for low voltages High Fidelity from Low Voltages Running opamps from a single +5V supply rail Opamps for 5V operation The NE5532 in +5V operation The LM4562 in +5V operation The AD8022 in +5V operation The AD8397 in +5V operation Opamps for 3.3 V operation Chapter 6: Filters Introduction Passive filters Active filters Low pass filters High pass filters Combined low pass & high pass filters Bandpass filters Notch filters All-pass filters Filter characteristics Sallen & Key lowpass filters Sallen & Key highpass filters Distortion in Sallen & Key filters Multiple-feedback bandpass filters Notch filters Differential Filters Chapter 7: Preamplifier architectures Passive preamplifiers Active preamplifiers Amplification and the gain-distribution problem Active gain controls plus passive attenuators Recording facilities Tone controls Chapter 8: Variable gain stages Amplifier stages with gain from unity upwards: single gain pot Amplifier stages with gain from unity upwards: dual gain pot Combining gain stages with active filters Amplifier stages with gain from zero upwards: single gain pot Amplifier stages with gain from zero upwards: dual gain pot Switched-gain amplifiers Chapter 9: Moving-magnet inputs: levels & RIAA equalisation Cartridge types The vinyl medium Spurious signals Other vinyl problems Maximum signal levels from vinyl Moving-Magnet cartridge sensitivities Overload margins and amplifier limitations Equalisation and its discontents The unloved IEC Amendment The ‘Neumann pole’ MM amplifier configurations Opamp MM input stages Calculating the RIAA equalisation components Implementing RIAA equalisation Implementing the IEC amendment RIAA series-feedback network configurations RIAA optimisation: C1 as a single E6 capacitor, 2xE24 RIAA optimisation: C1 as 3x10nF capacitors, 2xE24 RIAA optimisation: C1 as 4x10nF capacitors, 2xE24 RIAA optimisation: the Willmann Tables RIAA optimisation: C1 as 3x10nF capacitors, 3xE24 RIAA optimisation: C1 as 4x10nF capacitors, 3xE24 Switched-gain MM RIAA amplifiers Switched-gain MM/MC RIAA amplifiers Open-loop gain and RIAA accuracy Passive and semi- passive RIAA equalisation MM cartridge loading & frequency response MM cartridge-preamplifier interaction MM cartridge DC and AC coupling Noise in MM RIAA preamplifiers Hybrid MM amplifiers Balanced MM inputs Noise in balanced MM inputs Noise weighting Noise measurements Cartridge load synthesis for lower noise Subsonic filters Subsonic filtering: Butterworth filters Subsonic filtering: elliptical filters Subsonic filtering by cancellation Ultrasonic filters A practical MM amplifier: #3 Chapter 10: Moving-coil head amplifiers Moving-coil cartridge characteristics The limits on MC noise performance Amplification strategies Moving-coil transformers Moving-coil input amplifiers An effective MC amplifier configuration The complete circuit Performance Chapter 11: Tape replay The Return of Tape A brief history of tape recording The basics of tape recording Multitrack recording Tape heads Tape replay Tape replay equalisation Tape replay amplifiers Replay noise: calculation Replay noise: measurements Load synthesis Noise reduction systems Dolby HX-Pro Chapter 12: Guitar preamplifiers Electric guitar technology Guitar pickups Pickup characteristics Guitar wiring Guitar leads Guitar preamplifiers Guitar preamplifier noise: calculations Guitar preamplifier noise: measurements Guitar amplifiers and guitar effects Guitar direct injection Chapter 13: Volume controls Volume controls Volume control laws Loaded linear pots Dual-action volume controls Tapped volume controls Slide faders Active Volume controls The Baxandall active volume control The Baxandall volume control law A practical Baxandall active volume stage Low-noise Baxandall active volume stages The Baxandall volume control: loading effects An improved Baxandall active volume stage with lower noise Baxandall active volume stage plus passive control The Overlap Penalty Potentiometers and DC Belt-ganged volume controls Motorised potentiometers Stepped volume controls Switched attenuator volume controls Relay-switched volume controls Transformer-tap volume controls Integrated circuit volume controls Loudness controls The Newcomb and Young loudness control Chapter 14: Balance controls The ideal balance law Balance controls: passive Balance controls: active Combining balance controls with other stages Switched balance controls Mono-stereo switches Width controls Chapter 15: Tone controls & equalisers Introduction Passive tone controls Baxandall Tone Controls The Baxandall one-LF-capacitor Tone Control The Baxandall two-LF-capacitor Tone Control The Baxandall two-HF-capacitor tone control The Baxandall tone control: impedance and noise Combining a Baxandall stage with an active balance control Switched-HF-frequency Baxandall controls Variable-frequency HF EQ Variable-frequency LF EQ A new type of switched-frequency LF EQ Variable-frequency HF and LF EQ in one stage Tilt or tone-balance controls Middle controls Fixed frequency Baxandall middle controls Three-band Baxandall EQ in one stage Wien fixed middle EQ Wien fixed middle EQ: altering the Q Variable-frequency middle EQ Single-gang variable-frequency middle EQ Switched-Q variable-frequency Wien middle EQ Switchable peak/shelving LF/HF EQ Parametric middle EQ Graphic equalisers Chapter 16: Mixer architecture Introduction Performance factors Mixer internal levels Mixer architecture The split mixing architecture The in-line mixing architecture A closer look at split format modules The channel module (split format) Effect return modules The group module The master module Talkback and oscillator systems The in-line channel module Chapter 17: Microphone preamplifiers Microphone types Microphone preamplifier requirements Transformer microphone inputs The simple hybrid microphone preamplifier The balanced-feedback hybrid microphone preamplifier Microphone and line input pads The padless microphone preamplifier Capacitor microphone head amplifiers Ribbon microphone amplifiers Chapter 18: Line inputs External signal levels Internal signal levels Input amplifier functions Unbalanced inputs Balanced interconnections The advantages of balanced interconnections The disadvantages of balanced interconnections Balanced cables and interference Balanced connectors Balanced signal levels Electronic vs transformer balanced inputs Common mode rejection The basic electronic balanced input Common-mode rejection The basic electronic balanced input The basic balanced input and opamp effects Opamp frequency response effects Opamp CMRR effects Amplifier component mismatch effects A practical balanced input Variations on the balanced input stage Combined unbalanced and balanced inputs The Superbal input Switched-gain balanced inputs Variable-gain balanced inputs Combined line input and balance control stage with low noise The Self variable-gain line input High input-impedance balanced inputs The inverting two-opamp input The instrumentation amplifier Instrumentation amplifier applications The instrumentation amplifier with 4x gain The instrumentation amplifier at unity gain The instrumentation amplifier and gain controls The instrumentation amplifier and the Whitlock bootstrap Transformer balanced inputs Input overvoltage protection Low-noise balanced inputs Low-noise balanced inputs in action Ultra-low-noise balanced inputs Chapter 19: Line outputs Unbalanced outputs Zero-impedance outputs Ground-cancelling outputs: basics Ground-cancelling outputs: zero-impedance output Ground-cancelling outputs: CMRR Ground-cancelling outputs: send amplifier noise Ground-cancelling outputs: into a balanced input Ground-cancelling outputs: history Balanced outputs: basics Balanced outputs: output impedance Balanced outputs: noise Quasi-floating outputs Transformer balanced outputs Output transformer frequency response Output transformer distortion Reducing output transformer distortion Chapter 20: Headphone amplifiers Driving heavy loads Driving headphones Special opamps Multiple opamps Opamp-transistor hybrid amplifiers Discrete Class-AB headphone amplifiers Discrete Class-A headphone amplifiers Balanced headphone amplifiers Chapter 21: Signal switching Mechanical switches Input-select switching: mechanical The Virtual Contact: mechanical Relay switching Electronic switching Switching with CMOS analogue gates CMOS gates in voltage mode CMOS gates in current mode CMOS series-shunt current mode Control voltage feedthrough in CMOS gates CMOS gates at higher voltages CMOS gates at low voltages CMOS gate costs Discrete JFET switching The series JFET switch in voltage mode The shunt JFET switch in voltage mode JFETS in current mode Reducing distortion by biasing JFET drive circuitry Physical layout and offness Dealing with the DC conditions A soft changeover circuit Control voltage feedthrough in JFETS Chapter 22: Mixer subsystems Mixer bus systems Input arrangements Equalisation Insert points How to move a circuit block Faders Improving fader offness Post-fade amplifiers Direct outputs Panpots Passive panpots The active panpot LCR panpots Routing systems Auxiliary sends Group module circuit blocks Summing systems: voltage summing Summing systems: Virtual-earth summing Balanced summing systems Ground-cancelling summing systems Distributed summing systems Summing amplifiers Hybrid summing amplifiers Balanced hybrid summing amplifiers Balancing tracks to reduce crosstalk The multi-function summing amplifier PFL systems PFL summing PFL switching PFL detection Virtual-earth PFL detection AFL systems Solo-In-Place systems Talkback microphone amplifiers Line-up oscillators The flash bus Power supply protection Console cooling and component lifetimes Chapter 23: Level indication & metering Signal-present indication Peak indication The Log Law Level LED (LLLL) Distributed peak detection Combined LED indicators VU meters PPM meters LED bargraph metering A more efficient LED bargraph architecture Vacuum fluorescent displays Plasma displays Liquid crystal displays Chapter 24: Level control & special circuits Gain-control elements A brief history of gain-control elements JFETs Operational transconductance amplifiers (OTAs) Voltage-Controlled Amplifiers (VCAs) Compressors and limiters Attack artefacts Decay artefacts Subtractive VCA control Noise gates Clipping Diode clipping Active clipping with transistors Active clipping with opamps Noise generators Pinkening filters Chapter 25: Power supplies Opamp supply rail voltages Designing a ±15V supply Designing a ±17V supply Using variable-voltage regulators Improving ripple performance Dual supplies from a single winding Power supplies for discrete circuitry Large power supplies Mutual shutdown circuitry Very Large power supplies Microcontroller and relay supplies +48V phantom power supplies Chapter 26: Interfacing with the digital domain PCB layout considerations Nominal levels and ADCs Some typical ADCs Interfacing with ADC inputs Some typical DACs Interfacing with DAC outputs Interfacing with microcontrollers

About the Author :
Douglas Self studied engineering at Cambridge University then psychoacoustics at Sussex University. He has spent many years working at the top level of design in both the professional audio and hi-fi industries and has taken out a number of patents in the field of audio technology. He currently acts as a consultant engineer in the field of audio design.

Review :
"Self provides solid, well-explained technical information throughout the book, all gained from years of experience and a thorough understanding of the entire topic (...) His book exudes skilful engineering on every page, and I found it a very refreshing, enjoyable, and inspirational read (...) if you have the slightest interest in audio circuit design this book has to be considered an essential reference. Very highly recommended." - Hugh Robjohns, Sound on Sound Magazine "This book presents a large body of knowledge and countless insider-tips from an award-winning commercial audio designer (...) Douglas Self dumps a lifetime's worth of thoroughly-tested audio circuit knowledge into one biblical tome." - Joseph Lemmer, Tape Op