FIRST THE GOOD NEWS: In the first few chapters Slone has some good comments about many ideas promoted by high-end audiophile "subjectivists". He exposes many ideas as myths with no basis in fact. If you're someone who spent more than $20 for your speaker cables, prepare to be offended. He also does a decent job of covering the basics of amplifiers, the important specs, etc.



RE-HASH OF OTHER BOOKS? The two other big authors on this topic are Douglas Self and John Linsley Hood. Both have written multiple books and articles. Slone's book is newer than the earlier editions from both Self and Hood. In many ways, Slone seems to borrow heavily from the other two authors.



OUTDATED: Like the books by Self and Hood, much of Slone's book is devoted to chasing distortion out of the input and intermediate stages of an amplifier. Slone is proud of his input and voltage amp circuit designs touting them as "unbeatable". Such a bold claim was questionable in 1999 when he wrote the book and today you can buy the National LM4702 for $8 and it matches and even outperforms Slone's best designs. The LM4702 is especially DIY friendly saving a lot of work, grief, testing and parts cost. The LM4702 will provide a better end result than most any DIY effort with discrete parts. So it makes 75% of Slone's book a lesson in history rather than how to build a good amp.



NO CLASS D: Slone's book is dated in other areas as well. He states that class D amplifiers are not viable for audiophile use and probably never will be. That arguably wasn't true in 1999, and certainly isn't true today. Several class D products, like the ICE and BASH modules, have been widely praised by even the golden-eared audiophiles and are showing up in some very high-end designs. They're reliable, measure well and sound great but Slone wrongly dismisses the entire class.



CONFUSING: Slone uses odd abbreviations throughout the book almost as if he's trying only to be different from Self and Hood. The result only makes for confusion. For example he calls the output stage "OPS" and the voltage amplifier stage "VA stage". Self and Hood, for example, use the much more common term "VAS".



ARGUABLY WRONG: Slone states many things as fact, without providing any references, blind listening tests, or even sometimes any test data at all, to back up his bold claims. For example, he strongly states eliminating the DC blocking input capacitor is foolish and a very bad idea. Yet, National Semiconductor in their blind testing concluded: "In listening tests at National's sound room evaluating different circuit components used in the LM4702 demo amplifier, there was one part whose negative effect on audible signal quality was undeniable. A DC blocking capacitor on the input of the LM4702 degraded sound quality" (National App Note AN-1490).



NOT FOR NOVICES: Slone's book doesn't walk you through building even one of his designs. Some big things are missing. Nowhere, for example, does he provide a parts list (bill of materials) for any of his designs. Lots of details are missing like resistor power ratings, capacitor types and voltages, etc. And the company he references selling circuit boards appears to be out of business.



MOSFET LOVER: Slone is a huge fan of lateral MOSFET output devices. This is in direct opposition to Self, and virtually all commercial manufactures, who largely ignore them for some very valid reasons. He even goes so far as to boldly write things like "...all audiophiles would agree that an L-MOSFET OPS design would be the optimum choice if...". The last arguably successful MOSFET design was the Halfer DH series from the early 80's. In the nearly 30 years since then a lot has changed in amplifier technology but apparently not Slone's dated opinions.



BETTER DIY OPTIONS: If you're wanting to build a great DIY amplifier you're better off with either one of the many good class D modules or, if you prefer a more traditional class A/B design, the National LM4702 driver IC. Neither is covered in Slone's book. National and some of the Class D suppliers have excellent application notes for free and there's lots of DIY info on the web. National even has an app note for using MOSFETs with the LM4702.



SAVE MONEY: If you're mainly looking to save money, I'd forget DIY completely. Unlike in Slone's era, much has changed these days with the price of commercial products dropping. I don't think it's possible to build an amp that outperforms and costs less than an Emotiva or Outlaw unless you already have some of the expensive parts laying around. And if $300 for an Emotiva is still too much pro-sound amps start around $150 and used amps for even less. Apples-to-Apples, DIY can't touch these prices and I'd wager an Emotiva will match or beat anything in Slone's book in a blind listening test.



THEORY: If you're looking for a book that covers theory rather than practical designs, you're much better served by the Self or Hood books. Either author does a better job of covering the technical topics compared to Slone. Self and Hood extensively reference their theory and claims while Slone does not.



NOSTALGIA: Finally, if you want to build (or understand) an inferior "retro" amp for perhaps nostalgic reasons, or a musical instrument amp, this book might be useful and it's cheaper than the books from Self or Hood. Slone mentions some of the unique needs of pro/instrument amps and provides some designs that might be useful. But for home listening there are much better options (see above) that are easier, cost less, and perform better than his designs.



SUMMARY: Save your money and don't buy this book unless you're looking for nostalgic and/or musical instrument designs.