SOLDERING ON
Enhanced Sound: 22 Electronics Construction Projects for the Audiophile by Richard J. Kaufman. TAB Books Division of McGraw-Hill, softcover, 170 pp., $12.60.
Richard J. Kaufman's articles have appeared for years in Audio and are popular among those of us who actually take a soldering iron in hand occasionally. Small-scale projects suitable for an evening or weekend have been the subjects of his articles, and now he can add this book to his goal of, in one way or another, improving the sound of our systems. Examples of the Audio articles are "Build a Polarity Inverter" and "Build an Op-Amp Power Supply" from December 1987, two quick-build car projects ("Op-Amp Power Supply" and "Subwoofer Crossover") from the May 1989 issue, and more recently, "Build a Simple Surround Decoder" from June 1991. Kaufman's circuits tend to be simple, workable examples of how to achieve a given audio function in a relatively straightforward manner. They also have the strong appeal of using readily available, moderately priced, non-exotic parts. This makes the circuits easy to duplicate, with reasonable confidence that they will function as planned.
I should preface my remarks with the fact that I am reviewing a book dedicated to basic concepts I personally endorse. Quite simply, it is my own feeling that the audio world needs more and various such circuits, as examples of how-to, as idea stimulators, or just as continuing reminders that we as creators and builders (albeit on a small scale) can indeed alter and improve our own sonic fortunes. Not only do we need these reminders, we need them on a continuing basis and, at best, with an associated dialog of feedback experiences, application pros and cons, and the generally healthy exchange of ideas.
There could be a tendency to aim a book like this either too low or too high, in terms of the experience level required. Enhanced Sound strikes a reasonable balance here, with three introductory chapters on construction and semiconductor basics and then eight more chapters dealing with actual project examples, in some cases several in each. These chapters include such headings as Projects Without Power Supplies, Power Supplies, Preamps and Amplifiers, Basic Op-Amp Projects, Active Filters, Active Crossover Networks, Speaker Design Programs, and FM Antennas. The 22 project examples within them include passive and active preamps, tone controls, and even a power amplifier design.
At times, the art accompanying the circuits discussed is found lacking. For example, the RIAA response curve (Fig. 6-5) is so crudely drawn as to be almost meaningless (no label for the vertical axis, and the curve itself is not accurate). In other instances, there are missed connections or component values, or ambiguities in schematics (Figs. 5-5 and 6-3).
For parts callouts, Kaufman suggests relatively commonplace parts, which is generally fine for the overall context of the book. For example, TL072 op-amps are standard items, acceptable for general purposes, but some lower noise alternates should also be mentioned. Dedicated p.c. lay outs or boards are not available for the projects, but a functional alternate in the form of stuffing guides for Radio Shack boards can be purchased for every project and are available from Rivera, which also stocks all the individual resistors and capacitors.
The power amplifier presented is not discussed so much as a circuit "ready to build" but more as a typical design example, available from a kit vendor in the Orient (source specified in the appendix). This design, quoted as capable of 100 watts per channel into 8 ohms with proper supply, is strongly reminiscent of a Hafler DH-200 series but with a bipolar output stage. A table of parts is listed for it, however, presumably for those wishing to build the circuit from scratch. I would suggest anyone so inclined should check out the circuit thoroughly, though, as there appears to be a schematic connection dot missing at R14/C7 that should seemingly go to the collectors of Q3-Q5. (I note this apparent error in the hopes that few will actually suffer from it in building the circuit up.) In other chapters, Kaufman gets into examples of active filters, even including BASIC source code for multiple feedback filter circuits. Active crossovers are illustrated by several different types, including constant voltage and fourth-order Linkwitz-Riley styles.
Vented-box enclosure arrangements are also shown, with BASIC listings for computer programs to calculate a de sign using Thiele-Small parameters.
The book concludes with a chapter on FM antennas, which includes construction details for basic dipole types, a double-loop circularly polarized unit, and even a relatively exotic helical type. The appendix and index wrap it all up, the former by two pages of parts sources, while the index is three pages long.
As I stated initially, I like the basic idea of what Enhanced Sound is about, and I think Kaufman's choices for circuits and projects are good overall.
While I have some reservations about the publisher's quality control in letting some of the items mentioned slip through, one must decide individually how much these things get in the way.
The thing to bear in mind here is the overall utility and function of this book, as it presents a broad range of useful material. If you have enjoyed Kaufman's Audio articles, you may wish to look it over.
-Walter G. Jung
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The Down Home Guide to the Blues by Frank Scott and the staff of Down Home Music (6921 Stockton, El Cerrito, Cal. 94530). Softcover, 252 pp., $14.98.
For many years, Down Home has supplied the blues record buyer with discs that are largely impossible to find elsewhere. While this is their catalog, the text is by no means an unconsidered touting of the records they sell quite the reverse, and in fact, they include a clip-out coupon entitling you to a 15% discount on an order. For example, here's a line from a Leadbelly disc review: "Overall sound on this collection is a bit muffled but generally good." With more than 3,000 discs covered (I'll take their word for the count) and 100 record "Essential Selections" highlighted, it's pretty hard to go wrong buying this if you're a blues lover. E.P.
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Hearing: An Introduction to Psychological and Physiological
Acoustics, Second Edition by Stanley A. Gelfand, Marcel Dekker, Inc., hardcover,
535 pp., $55.
Despite the statement in Harry Levitt's Foreword that this book is "up to date with respect to new developments in all aspects of the field of hearing science," it falls considerably short of this claim. Stanley A. Gelfand presents a reasonably good view of the state of thinking as it existed 20 to 30 years ago but provides very little information concerning the technological advances, theoretical developments, and experimental approaches that have appeared in the field of hearing science since then.
The book begins with a chapter on the physics of sound. There follow discussions of the anatomy of the ear and the auditory pathways, of the ways in which sound is conducted to the inner ear, and of the functioning of the inner ear. Further chapters are concerned with the functioning of the auditory nerve and of the higher auditory path ways. These chapters focus on the response of the auditory system to simple signals and do not consider the recent findings showing that the hearing mechanism can respond in highly sophisticated ways to complex sounds and patterns of sound.
There are several chapters on psychoacoustics which deal almost exclusively with simple detection and discrimination tasks. Virtually no mention is made of the perception of auditory and musical patterns, of the processes involved in the identification of musical instrument timbre and other sound qualities, or of the ways in which temporal patterns of sound are perceived. A final chapter addresses speech perceptions, and this again draws almost exclusively on earlier findings.
In summary, this book presents a rather depressed account of research and theory concerning the hearing mechanism and does not attempt to consider the exciting new approaches being taken, discoveries being made, and technological capabilities that are available to researchers in the field. Perhaps the third edition will prove more inspiring.
-Diana Deutsch
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The Roots of the Blues: An African Search by Samuel Charters. Da Capo Press, softcover, 152 pp., $10.95.
I first came into contact with musicologist/writer Sam Charters' work about a quarter century ago when I discovered a three-LP set, Chicago/The Blues/Today! One day, I hope to publish an interview of him.
This little book was originally published in 1981 by Marion Boyars, Inc., and has nine photos and a simple map of West Africa. Properly, it ought to be accompanied by the recordings Charters did during his trips, but they do not seem to be available presently (though similar music is available on Playa Sound's Senegal: The Griots' Kora [PLS 65079], distributed by Allegro Im ports). I suspect, however, that other later recordings, using more modern equipment, particularly DATs, will be more satisfactory.
Unhappily, Charters didn't find the source of the blues, but let him tell it:
I had come to Africa to find a kind of song, to find a kind of music and the people who performed it. . . . I'd come looking for a kind of song, and even if I hadn't really found it, I'd found the people who sang it. The journey I'd begun had taken me to places I hadn't expected, and the ideas and attitudes I had at the end of it were different from where I'd started.
It would have been nice if Charters had found the roots, but at the end of the book my ideas and attitudes were different . . . and that made it a nice journey.
- E.P.
(adapted from Audio magazine, Jul. 1992)
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