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PUBLISHER’S LETTER www.siliconchip.com.au Publisher & Editor-in-Chief Leo Simpson, B.Bus., FAICD Production Manager Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Robert Flynn Ross Tester Rick Walters Reader Services Ann Jenkinson Advertising Enquiries Rick Winkler Phone (02) 9979 5644 Fax (02) 9979 6503 Mobile: 0414 34 6669 Regular Contributors Brendan Akhurst Rodney Champness Garry Cratt, VK2YBX Julian Edgar, Dip.T.(Sec.), B.Ed Mike Sheriff, B.Sc, VK2YFK Philip Watson, MIREE, VK2ZPW Bob Young SILICON CHIP is published 12 times a year by Silicon Chip Publications Pty Ltd. A.C.N. 003 205 490. All material copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Printing: Macquarie Print, Dubbo, NSW. Distribution: Network Distribution Company. Subscription rates: $59 per year in Australia. For overseas rates, see the subscription page in this issue. Editorial & advertising offices: Unit 8, 101 Darley St, Mona Vale, NSW 2103. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 9979 5644. Fax (02) 9979 6503. E-mail: silchip<at>siliconchip.com.au ISSN 1030-2662 * Recommended and maximum price only. 2  Silicon Chip Faith & hope are no substitute for measurements As time goes on and new technology presents consumers with ever more gee-whiz choices, it is surprising just how many people still have an abiding interest in hifi amplifiers and speakers. In one aspect this is not surprising though, because it really is only in the area of amplifiers and speakers that hifi enthusiasts have an opportunity to have an input in producing their “ultimate system”. Designing and building your own hifi equipment is very satisfying, for all sorts of reasons. That said, I am quite often button-holed by people who want me to consider their latest amplifier creation which sounds, to them, truly wonderful. Typically, this amplifier will be a compilation of the design features of notable designers and reviewers from around the world. It may have low feedback or no feedback, to give really “natural” sound, or it may have lots of feedback and have a very fast slew rate (maybe 300V/µs) to give a really “fast” sound. According to the person’s beliefs, the amplifier may use Mosfets because of their indestructibility or bipolars because they sound “cleaner” and so on. Whatever the particular person’s design philosophy, he will always be adamant that it is the best system he has ever heard (perhaps it is) and that it is probably the best available in the world (highly unlikely). But when I ask about distortion measurements, the conversation always gets bogged down. In fact, it often turns out that no measurements have been made at all, not even for power output and frequency response. Now while these people may genuinely believe that they have produced a masterpiece, the odds of them doing so, without having made exhaustive measurements to confirm their beliefs, are extremely long. In fact, it’s just not possible. We have found on any number of occasions, the number of variables effecting an amplifier’s performance is very large and even the position of a single supply or signal wire can have a major effect on the distortion and therefore, the sound quality. Moreover, if you randomly vary something, you usually get a worse result! So if you make any alteration to a design, you must then do exhaustive measurements to see if the results are better. But try and tell this to anyone who is convinced of the beauty of his own design and you will usually not get a good reception. In fact, it is better to just nod sagely and say something vague and complimentary. So if you are in the same situation and someone tells you that he has produced a wonderful new amplifier or speaker design, by all means have a listen to it. It will probably be very enjoyable. But if measurements haven’t been made somewhere along the line, there could be a large proportion of delusion in the enjoyment. Leo Simpson