The further adventures of a Self-made amplifier
By Joshua Israelsohn -- EDN, January 23, 2003
When a fire alarm goes off in your office, what do you do? What you're supposed to do is immediately leave your desk and walk "in an orderly fashion" to the nearest emergency exit. But what you most likely actually do is grab your laptop, cell phone, PDA, briefcase, car keys, and jacket; make sure you have your wallet; pack everything up; and then head out the door. During your stroll to the exit you meet up with many of your co-workers who are similarly tardy and similarly equipped.
I do things just a bit differently.
I figure the laptop is backed up to the server, the cell phone and PDA have been out of date since I've owned them, and, unless I'm working out of our Greenland office, I can probably do without my jacket. What I grab first is the empty box that lives under my desk, and I place into it the six or seven books that I'd rather not do without—what I call "foundation" books. Then, I grab the box and my car keys, and I'm out the door before most folks I work with have undocked their laptops.
A couple of years ago, I made room in the box for another volume—the Audio Power Amplifier Design Handbook by Douglas Self—available now in a new third edition from Newnes (Picture). This $39.99 book (ISBN 0-7506-5636-0) has many useful traits to recommend it, not the least of which is the author's clarity and uncommonly engaging writing style. This clarity extends beyond the prose style to the organization and presentation of the core technical material including, for example, a remarkable disintegration of an amplifier's harmonic-distortion terms, their sources, and their relationships to design decisions. In addition to numerous schematics, Self includes performance plots of the various structures he presents that form the bases for concise comparisons between topological options.
This is a true handbook in the "just-about-everything-you'd-want-to know-in-one-volume" sense of the word. It is decidedly not a cookbook. It is a resource for those who would like to gain some of Self's deep understanding of the subtleties of amplifier design—not those who want an easy schematic to rip off. The third edition continues along the same path its predecessors forged. It adds a chapter on Class G amplifiers—circuits that beat the efficiency of standard linear amplifiers by operating on and switching between multiple supplies as the signal level demands. Also new in this edition is Self's trimodal-amplifier design that can operate in class A, AB, or B.
Elsewhere in the third edition, the author also treats thermal issues, amplifier and speaker protection, grounding, and layout concerns, taking this handbook far beyond a theoretical textbook treatment to include solid information about the practical requirements of building high-quality, reliable amplifiers.
Newnes, www.newnespress.com.
