Douglas Self’s excellent technical reference book for solid-state audio-gear designers has been updated.
Since reviewing the original version of this superb book back in June 2011, I’ve found myself referring to it regularly. For those not aware of author Douglas Self’s credentials, he studied engineering at Cambridge and psycho-acoustics in Sussex, worked at the sharp end of professional mixing console and high–end hi–fi design for many years, and has several audio-technology patents to his name. He now works as an audio design consultant, and has authored several excellent audio electronics books, including the Audio Power Amplifier Design Handbook, and Self On Audio. This new edition of Small Signal Audio Design (SSAD) expands considerably on its predecessor, with roughly 200 more pages and five more chapters! I’ll concentrate on those new additions — to gain a picture of the full breadth of content you can access the original review free on our web site (http://sosm.ag/douglas-self-ssad-1st-ed).
The opening chapter on electronic basics is unchanged, but the second chapter on electronic components (and their foibles) has gained 10 pages, and Chapter 3 on discrete transistor circuitry has been expanded three-fold. The first all-new chapter (5) concerns the use of low-voltage op amps running on 5V and 3.3V single-rail supplies (for battery- and USB-powered devices, for example). This includes a typically thorough evaluation of the performance of suitable op amps, and some helpful design tips and strategies, particularly regarding grounding practices.
The most developed section of the book, by a considerable margin, is the section on preamp design for record-player pickups, which has easily doubled in size, with the original and new material subdivided into five chapters instead of two. Chapter headings now cover moving magnet levels and RIAA equalisation, archival and non-standard EQ (for 78s, wax cylinders and so forth), discrete circuitry stages, noise and distortion, and moving-coil head amplifiers. As Self says in his preface, “the fact that it takes four whole chapters to cover the process of extracting a reasonable signal from a record groove indicates to me that there is something amiss with the whole concept.” To which I must add that that’s without even considering the implausible mechanical issues!
Another chapter which has been expanded and split into two concerns volume controls, where the original section on active volume controls has been expanded by 10 pages, and the balance-control portion allocated a chapter of its own. The Tone Control and EQ chapter has also been expanded to include some very clever new low-impedance designs which minimise noise. The chapter on mixers gains more on routing systems, balanced summing amps, and level-indication techniques too, and the audio-interfacing chapters now include more on using instrumentation amplifier techniques to advantage, as well as some clever output topologies including ground-cancelling and zero-distortion transformer techniques. Headphone amplifiers gain an entirely new chapter, as well, covering hybrid solutions and class-A designs with ultra-low distortion, while the final chapter on interfacing with the digital domain now examines the use of micro–controllers for ‘housekeeping’ and other key functions.
Douglas Self provides solid, well-explained technical information throughout the book, all gained from years of experience and a thorough understanding of the entire topic, and all verified by measurement and practical applications in the field. His book exudes skilful engineering on every page, and I found it a very refreshing, enjoyable and inspirational read. Self writes in his preface that he dares to hope that he has moved analogue audio design a bit further forward. He certainly has for me, and if you have the slightest interest in audio circuit design this book has to be considered an essential reference. Very highly recommended. Hugh Robjohns