The Audiophile's Project Sourcebook: 120 High-Performance Audio Electronics Projects

By G. Randy Slone

THE AUDIOPHILE’S PROJECT SOURCEBOOK

Build audio projects that produce great sound for far less than they cost in the store, with audio hobbyists’ favorite writer Randy Slone. In The Audiophile’s Project Sourcebook, Slone gives you—

• Clear, illustrated schematics and instructions for high-quality, high-power electronic audio components that you can build at home
• Carefully constructed designs for virtually all standard high-end audio projects, backed by an author who answers his email
• 8 power-amp designs that suit virtually any need
• Instructions for making your own inexpensive testing equipment
• Comprehensible explanations of the electronics at work in the projects you want to construct, spiced with humor and insight into the electronics hobbyist’s process
• Complete parts lists

"The Audiophile's Project Sourcebook" is devoid of the hype, superstition, myths, and expensive fanaticism often associated with 'high-end' audio systems. It provides straightforward help in building and understanding top quality audio electronic projects that are based on solid science and produce fantastic sound!

THE PROJECTS YOU WANT, FOR LESS

Balanced input driver/receiver circuits
Signal conditioning techniques
Voltage amplifiers
Preamps for home and stage
Tone controls
Passive and active filters
Parametric filters
Graphic equalizers
Bi-amping and tri-amping filters
Headphone amplifiers
Power amplifiers
Speaker protection systems
Clip detection circuits
Power supplies
Delay circuits
Level indicators
Homemade test equipment

• Language: English
• Publisher: McGraw-Hill Education
• Release date: Nov 20, 2001
• ISBN: 9780071706223

Book preview

THE AUDIOPHILE’S PROJECT SOURCEBOOK

THE AUDIOPHILE’S PROJECT SOURCEBOOK

G. Randy Slone

Copyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved. Except as permitted under the United States Copyright Act of 1976, no part of this publication may be reproduced or distributed in any form or by any means, or stored in a database or retrieval system, without the prior written permission of the publisher.

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CONTENTS

Preface

Acknowledgments

Chapter 1 Establishing the Basics

The Psychological Tie Between Sound and the Human Mind

Why Audio Electronics?

The Goal of High-Performance Audio Equipment

Harmonic Distortion

What About Intermodulation Distortion?

Noise

Frequency Response (Bandwidth)

Slew Rate

Phase Considerations

Additive Effects in Audio Systems

A Final Word on Performance

Safety Considerations

Chapter 2 Beginning at the Beginning

To Balun or not to Balun? That Is the Question!

Solid-State Balun Variations

Jumping from the Pot onto the Step Ladder

Chapter 3 Audio Preamplifier Systems

Passive Preamplifiers in an Active World

Conventional Preamplifier Systems

Chapter 4 Audio Filter Circuits

Domestic Hi-Fi Considerations

Professional Considerations

Audio Filter Circuit Projects

Chapter 5 Headphone Amplifiers

Why Listen to Music through Headphones?

Generalities of Headphone Systems

Headphone Amplifier Projects

Chapter 6 Audio Power Amplifiers

Audio Power Amplifier Performance Goals

Audio Power Amplifier Classes

Vacuum Tube Power Amplifiers versus Solid-State Power Amplifiers

Audio Power Amplifier Fundamentals

Audio Power Amplifier Cookbook Designs

Bias Adjustment Without the Use of a Distortion Analyzer

Some Final Thoughts on Audio Power Amplifier Construction

Chapter 7 Power Supplies

Power Supplies for Audio Power Amplifiers

An Evaluation of the Three Main Types of Power Amplifier Power Supplies

Choosing a Power Supply Type for an Audio Power Amplifier Application

Power Transformer Considerations

Transformer EMI Problems

Rectification

Power Supply Fusing

Reservoir Capacitors

Typical Power Supply Designs for Audio Power Amplifiers

Power Supply Calculations

Power Supplies for Signal-Processing Applications

Chapter 8 Protection Circuits

DC and Transient Speaker Protection

Soft-Start Circuits

Clip Detection Circuits

Chapter 9 Miscellaneous Audio Circuits

Display Circuits

Phase Control

Delay Effects

Chapter 10 General Construction Information

Hum, Noise, and Grounding Considerations

General Wiring Considerations

Printed Circuit Board Construction Techniques

Making Printed Circuit Boards by Hand

Making Printed Circuit Boards by Computer/Photographic Methods

Heatsinks

Project Enclosures

Appendix A Audio Electronics Terminology

Appendix B Sources of Information and Materials

Appendix C PC Board Artwork

Index

PREFACE

The Audiophile’s Project Sourcebook is intended for electronics hobbyists and audiophiles who enjoy constructing their own high-end audio equipment, and who also desire a more complete understanding of the fundamentals involved with audio design. In addition, the information contained in this book will equip audio enthusiasts with the practical knowledge for experimentation and modifications to existing audio equipment, as well as clarifying issues of application compatibility.

A well-rounded variety of domestic and professional audio projects is provided, including preamplifiers, filter circuits, headphone amplifiers, power amplifiers, effects circuits, power supplies, protection circuits, and display circuits. For the most part, these projects represent the state of the art in performance capabilities, and will exceed the performance parameters of most commercially available equipment. In addition to the complete schematics and technical descriptions, I have provided the PC board artwork and layout illustrations for many of the more complex designs.

I have assumed that the reader is experienced in the fundamentals of electronics and electronic construction, but I have made few assumptions regarding the reader’s expertise relating specifically to audio electronics. Appendix A provides a reasonably exhaustive clarification of audio electronics terms and modern buzz words as a further barrier against confusion.

The Audiophile’s Project Sourcebook is for hobbyists and audio-philes who have been discouraged by the apparent schism between audio professionals and extravagant esoterics. It is designed to help anyone experience the ultimate in sonic quality at a reasonable expense. The concepts and principles presented are not subjective, mythical, or traditional; they are scientific and extensively supported with provable analysis. Many readers will be pleasantly surprised at the low cost involved with even the best audio systems.

Above all, I have directed this book toward people who want to experience the fun, satisfaction, and fulfillment of superb and practical electronic projects (not to mention the significant cost savings). This text is not infested with watered-down demonstration or educational projects—it is a sourcebook of impressive, high-performance designs that lend legitimacy to the reader’s construction efforts. I sincerely hope that many will enjoy it and benefit from it.

ACKNOWLEDGMENTS

As a Christian, my first and foremost expression of appreciation belongs to my Lord and Savior, Jesus Christ, who keeps me and assists me in all honorable and productive goals. Also along the personal vein, a special debt of gratitude goes out to my wife, Mary Ann, who somehow manages to provide me with great measures of understanding and encouragement, even though she seldom understands what the heck I’m doing.

From the professional perspective, I am greatly indebted to my friend and associate at ZUS Audio, Russell Torlage, for his continual feedback and support of this project. A heartfelt thanks also goes out to Joe Koenig, Luis Alves, and the exemplary team at Electronics Workbench for their assistance in many problematic technical areas.

The heart of this book has been beating in audiophiles for the past four decades, so the majority of credit for this work really belongs to many pioneers, both past and present. Progress in the audio fields is effectively a group effort, with many excellent audio engineers and dedicated hobbyists deserving the majority of credit.

And finally, all of my efforts and support would be meaningless without the professionalism and expertise provided by the incomparable group at McGraw-Hill. I am greatly indebted to their progressive leading and encouragement.

G. Randy Slone

THE AUDIOPHILE’S PROJECT SOURCEBOOK

CHAPTER 1

ESTABLISHING THE BASICS

It is prudent to establish a basic foundation of concepts and goals as an opening prelude to this textbook. It is only fair to begin with a few brief comments that lend legitimacy to the serious time and money invested in the audio fields by many dedicated hobbyists and professionals, followed by a brief discussion of the common denominators inherent to all audio circuit designs.

The Psychological Tie Between Sound and the Human Mind

For a variety of reasons, sound is often placed on the back burner of human senses—we have the tendency to take it for granted. It is common to associate the importance of a sense with our ability to function without it. From this perspective, most every person will acknowledge our sense of sight as being of paramount importance, which is undoubtedly true. But have you ever taken a few moments to seriously consider how tightly your sense of hearing is integrated into the deepest recesses of your very being?

For example, when was the last time that you had an experience of such beauty that you felt the tendency to cry? Was it due to something you saw or something you heard? Are the majority of the most profound events in your life associated with things you heard or things you saw? Does a beautiful painting incite the same levels of emotional swell inside of you as a beautiful song? How many musical CDs do you own compared to the number of artistic paintings in your home? There is no question that the same emotional heights reached at sporting events can also be seen at musical concerts. Fan clubs established for famous musicians have equal enthusiasm with fan clubs devoted to movie stars. From the perspective of the effect generated in our lives, it would be difficult to assign a greater degree of importance to either sound or sight.

Hundreds of years before the birth of Christ, Aristotle (BC 384–322) offered a somewhat enigmatic statement, Why do rhythms and melodies, which are composed of sound, resemble the feelings; while this is not the case for tastes, colors, or smells? Those professionals who have undertaken serious research into the emotional, psychological, and spiritual connections between sound and human response (called psychoacousticians) have discovered profound relationships that are not fully documented or adequately understood. Such underfunded research continues as I write this text. Even with the shortcomings of understanding associated with psychoacoustics, it is a well-documented fact that for thousands of years (presumably since the beginning of humankind), music and song have been the fundamental basis for celebration, entertainment, religious worship, and almost every facet of recreation in general. Patriotic song has always been a tool for unifying a large mass of people in nationalistic fervor. Drums have been used by civilizations all over the world, throughout history, to trigger aggressive tendencies as preparation for war, and trumpets have traditionally voiced the battle cries. Every significant cause has an associative song. Angels are associated with song and music throughout the Bible, and Christmas music is the heart of the yearly holiday season. We listen to music in our homes, cars, and businesses; we even wear portable tape players while jogging. There is always a multitude of boom boxes at the beach, stereo systems at parties, background music in commercial businesses, and even elevator music in elevators!

The physics relevant to sound is a fascinating study to undertake. The human ear and eye are both incredible at their sensitivity and dynamic range. For example, the eye is capable of perceiving a single photon, while the ear is capable of hearing a sound created by air moving over a distance equal to the radius of a hydrogen atom! Comparing both of these sensitivity levels to the brightest flash of light or the loudest boom of sound, the dynamic range of our audio/video senses is approximately 1000 million times. However, when we compare the bandwidth of light to audio, the difference is quite dramatic. The entire visible light spectrum is concentrated into approximately one octave of bandwidth, whereas the audio spectrum spans 10 octaves. Here is another interesting thought. We see things in three dimensions—height, width, and depth. How many dimensions do you listen in? I’m not sure that anyone has accurately pinned down that answer yet.

Sound is a survival sense, a tool of education and communication, and an artform. Threatening sounds warn us of impending danger, we listen to our educators and verbally converse with our family and peers, and we appreciate beautiful music as we appreciate a classic painting, a fine glass of wine, or a gourmet meal. It is difficult to place a relative importance on the effect of sound in our lives, and it is abstract, to say the least, to attempt to understand why a variety of frequencies, harmonic qualities, sound pressure levels, and periodical rhythms can be summed together to stir our deepest emotional nature. I’m confident that an improved understanding of the human psychology relative to sound will emerge as more research is continued in the field of virtual reality (VR), since aural simulation will play a dominant role in the overall VR effect. The future of audio in our lives should be very, very interesting.

Why Audio Electronics?

Most individuals who are deeply interested in achieving high-quality performance from their audio equipment (commonly called audiophiles) have a natural and logical interest in the mechanics of sound. In the beginning, such interest may manifest itself in simpler, less technically oriented tasks, such as experimenting with speaker cables, adding commercial subwoofer units, or auditioning differing program formats. However, if the audiophile’s interest is sufficiently fueled by messing around with the easier stuff, the natural progression is to become involved with the deeper, more complex areas of audio electronics. To aid the audiophile in this endeavor, there is a consistent outpouring of hobbyist material, in the form of books and periodicals, which serves to keep the interest level sustained while simultaneously training the audiophile in both practical experience and technical prowess. I am repeatedly amazed at the technical knowledge of many audio electronic hobbyists who have never received any formal education in the field of electronics. Oftentimes, they appear to have a better practical knowledge of the field than many formally trained engineers.

As a logical extension of becoming highly proficient in the audio electronics field, there are a variety of professional directions to pursue. Most notable audio engineers started out as weekend hobbyists, and later discovered that they could convert their beloved hobby into a lucrative career. Many audio equipment manufacturers have started from the same humble beginnings. Fortunately, it isn’t necessary to develop a complete line of audio products to achieve such a goal. Rather, it is usually more practical to devote your primary attention to one small facet of the industry that you have the talents to excel in. For example, I have a friend who began by devoting his hobby energies toward developing high-performance passive crossover networks for speaker systems. After investing the time and money to develop a good reputation for himself, he developed a full-time career in manufacturing a variety of crossover networks (and associated components) for the audio marketplace. If you have a great love for audio electronics, the goal of turning your favorite pastime into a profitable career is certainly a strong motivating force to continue and grow in your capabilities.

Most individuals who purchase this book will probably not harbor any aspirations of developing a career for themselves in the field of audio electronics. But from the hobbyist perspective, there are many other motivational factors that come into play as time progresses. One factor is the extraordinary monetary savings that can be realized by building your own equipment.

It is no secret within the electronics manufacturing environment that the materials cost of a product may only represent 10% (or less) of its final selling price. The reasons for this situation are simple. First, the R&D (i.e., research and development) costs of the product must be reclaimed in the selling profit. Second, the labor costs in the manufacture and assembly of the item must be added. Third, the wholesale and retail merchants must receive their profit, along with the manufacturer. And finally, there are marketing, packaging, shipping, and technical support costs that must be added. If the typical audio electronics hobbyist has the necessary technical information, coupled with a sufficient degree of assembly experience, it is possible for the hobbyist to realize a cost savings of 100% to 1000% in comparison to equivalent commercial equipment. Recognizing that an elaborate high-end domestic audio system may cost up to $5000, or more, the savings incurred by constructing much of the equipment in one’s spare time can add up to a substantial amount.

Another motivational factor for being an audio electronics hobbyist is the capability of constructing many items that may not be commercially available (or exorbitantly expensive and/or difficult to obtain). Many audio electronics books or periodicals contain construction and technical information detailing unique amplifiers, preamplifiers, speaker systems, and many other hardware items, which simply may not be available on the commercial market. In many cases, these items may be superior to commercial units, or they may fix a unique problem that is highly application dependent. In any event, it is enjoyable, interesting, and gratifying to construct a variety of these projects. And it never hurts to bolster your ego a little by being able to say to your friends, I built this myself. (Be careful with such harmless boasts—they often backfire! It isn’t unusual to have a dozen friends come back at you with the request, Will you build one for me, considering the fact that we’re such good friends? There goes your spare time for a month!)

One of the strongest motivational factors among audio electronics hobbyists is the fact that they can actually construct audio equipment that is audibly superior to commercial equipment. Manufacturers must remain as competitive as possible, and this results in a large quantity of compromises in the end products. Also, for the most part, the larger manufacturers have not invested very much money into research and development of superior audio products. The result is that the big manufacturers are still producing audio equipment representing designs of two decades ago, even though significant advances have been made since then. I should mention here that I am not including the high-end audio equipment manufacturers in the same category as the larger, more diversified electronic manufacturers. Many of the high-end manufacturers are investing bundles of money in research, and this is clearly evident in the price tag. Within this same context, I should also mention that not all so-called high-end manufacturers are producing high-performance equipment. The actual performance of some high-end audio equipment in the marketplace today would have been considered poor as far back as the 1960s, so the purchase of such equipment is really a buyer beware situation.

Another motivational factor for getting involved with audio electronics is that it is one of the few remaining electronic fields open to the do-it-yourselfer. In the good ole days of being an electronics hobbyist, it was possible to build your own color television sets, radios, shortwave sets, or almost anything based on electronics. (If you happen to be a younger reader, you may find it incredible to believe that anyone could build his or her own TV set. However, back in the 1970s, the Heathkit Company offered some excellent-quality TV kits that were successfully constructed by many enthusiasts.) With the advent of our modern mass production techniques, coupled with the desire for higher performance in a smaller size, it has become impossible for the weekend hobbyist to construct or work on most electronic equipment. Few home labs contain elaborate surface-mount reworking stations, and the typical multilayer PC board is a throw-away item. The traditional home-town TV and radio repair shops have all but disappeared, because modern electronic equipment is not really manufactured to be repaired—it is meant to be replaced. For the most part, the enthusiasm of the modern electronics hobbyist is diminished due to the inability to build anything impressive or practical in the home arena. The major exception to this rule is the field of audio electronics.

Believe it or not, there is another field of electronics besides the digital and communications fields—it’s called analog! (Excuse my sarcasm.) It is common, at present, to encode much of our audio program material into digital formats, such as used in conjunction with CD, DAT, and MP3 programs. However, the accurate high-level reproduction of such material requires analog processing, so the vast majority of all domestic and professional sound systems will continue to rely on linear techniques. We will go into this subject in more detail later on in this text, but for now, allow me to simply state that there are certain laws of physics that will continue to force the field of audio electronics to remain in the analog domain. Past attempts at integrating, downsizing, and miniaturizing high-performance audio equipment have not met with a great deal of success. Consequently, these factors add up to a situation that allows the home-brew hobbyist to actually compete against the large industrialized manufacturers, and win!

It should also be noted that a considerable number of advancements in the design of superior audio equipment have been made by the at-home hobbyist. This illustrates another unique facet of the audio electronics field. It is doubtful that you would have the capabilities of making a breakthrough discovery in the field of particle physics or high-density RAM memory development within the confines of a home-based electronics lab, but it is very possible for the at-home hobbyist to refine and perfect a better audio electronics design. This is due to the fact that audio equipment, for the most part, is dependent upon discrete component construction, since the requirements of high voltages, high slew rates, and the comparatively high-power dissipation factors require such construction. Also, I can state with a great deal of confidence that this situation is not likely to change in the near future (again, due to certain insurmountable limitations of physics). Such a situation results in mandatory construction techniques that allow the audio electronics hobbyist to utilize components and materials that he or she has the capability of working with, and all the while, the definite (although elusive) possibility exists that a design advancement could be accomplished. In the case of many audio electronics hobbyists, the motivation to construct a better piece of equipment is the driving force behind their efforts. (There are few pioneers left in the world today, but they are rampant in the field of audio electronics!) We should not conclude, however, that such an individual will suffer the pangs of failure if such a goal is never realized—it is the excitement of the possibility that adds spice to the hobby. The audio electronics hobbyist looks at a handful of electronic components in the same manner that a professional writer looks at a blank sheet of paper—the potential is there, and it’s just a matter of getting it down right!

We live in an age wherein it is increasingly difficult for the do-it-yourselfer to achieve the pride and self-gratification of an impressive homemade project. Time is at a premium, and many fields have grown too complex for the typical hobbyist. I often receive feedback from audiophiles who spend hundreds of dollars in having customized control knobs machined for their amplifiers. It isn’t uncommon for an enthusiastic audiophile to spend countless hours hand finishing a custom walnut cabinet to house a new project. From my perspective, such behavior isn’t any more extreme than the woodworking hobbyist who spends a month’s worth of spare time making a new coffee table for the living room (considering that an automated machine could probably turn out one in less than 5 minutes). I suppose the creative spirit within all of us is the driving force to build, construct, and accomplish a goal that we can appreciate and take pride in. I hope this book will incite you to daydream at times, visualizing the new master audio project that will embody a little of yourself, or a new concept with the potential of revolutionizing the audio industry. Dreams are adrenaline for the human spirit, and such dreams are, in themselves, an excellent motivation.

I have come to appreciate the fact that there are many good reasons to become an audio electronics hobbyist, some professional, some economical, some educational, some creative, or a combination of all of the aforementioned. Audio electronics is a hobbyist field that is continually progressive, adaptable to any budget, personally gratifying, and I can guarantee that it will still be around long after this textbook has become obsolete.

The Goal of High-Performance Audio Equipment

The trouble with most people is not what they don’t know, but what they know for certain that isn’t true.

—MARK TWAIN

Upon first consideration, the typical person would probably assume that the field of audio electronics is a highly scientific one, since we normally consider the broad field of electronics, in general, to be the crowning glory of our present state of advanced scientific technology. That assumption isn’t necessarily true, although it certainly should be. In reality, the field of audio electronics is inundated with myth, sonic folklore, and a pseudoreligious type of mainstream indoctrination. Audio electronics is the only electronic field that I