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SILICON SILIC CHIP www.siliconchip.com.au Publisher & Editor-in-Chief Leo Simpson, B.Bus., FAICD Production Manager Greg Swain, B.Sc. (Hons.) Technical Editor John Clarke, B.E.(Elec.) Technical Staff Ross Tester Jim Rowe, B.A., B.Sc Nicholas Vinen Photography Ross Tester Reader Services Ann Morris Advertising Enquiries Glyn Smith Phone (02) 9939 3295 Mobile 0431 792 293 glyn<at>siliconchip.com.au Regular Contributors Brendan Akhurst David Maddison B.App.Sc. (Hons 1), PhD, Grad.Dip.Entr.Innov. Kevin Poulter Dave Thompson SILICON CHIP is published 12 times a year by Silicon Chip Publications Pty Ltd. ACN 003 205 490. ABN 49 003 205 490. All material is copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Printing: Hannanprint, Warwick Farm, NSW. Distribution: Network Distribution Company. Subscription rates: $105.00 per year in Australia. For overseas rates, see our website or the subscriptions page in this issue. Editorial office: Unit 1, 234 Harbord Rd, Brookvale, NSW 2100. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 9939 3295. E-mail: silicon<at>siliconchip.com.au ISSN 1030-2662 Recommended and maximum price only. 4  Silicon Chip Publisher’s Letter SMDs present challenges and opportunities For some years now we have been confronted with the reality that surface mount devices (SMDs) are rapidly supplanting through-hole components, ie, components with leads. In many cases, new electronic components are now not released in through-hole versions, so if we want to use these new devices in our projects, it is SMD or nothing. We know that some readers do not like SMDs, because they are much smaller, can be more difficult to handle and to solder – or at least that is how some people react. In fact, in some ways, SMDs are easier to handle than through-hole components. Yes, they are smaller but you don’t have to bother with poking tiny leads through holes in the PCB and you don’t have to worry about them falling out of the PCB when you flip it over to solder the components. Nor do you have to clip off the pigtails and so on. You can install all the SMDs required on one side of the PCB in one go. It can actually be quicker than assembling the same circuit with conventional through-hole components and arguably, the finished article looks better. Yes, you do need very good vision or if you are not so fortunate (with the keen eyesight of the young), you need magnifying aids. But realistically, such aids have always been required if you are to properly inspect your soldering in any case. So that covers the challenges. Then there are the opportunities to consider. One reader in this month’s Mailbag pages has asked about the possibility of designing PCBs which can be used in a variety of different projects, with the same powerful surface-mount microprocessor surrounded by a bunch of through-hole components, some or all of which may be installed, depending on the features required. Well, we think that is such a good idea that we have already done it, in projects featured in the November 2013, February 2014 and October 2014 issues. However, we did not make a big thing about it at the time because it seemed like a logical process and not an earth-shaking development. The reader who made the suggestion could be forgiven for not realising that the idea had already been used. It’s a bit like having passed through a small country town at speed – blink and you might have missed it. But SMDs offer other opportunities and a great example is evidenced by the PCB of the new Ultra-LD Mk4 high-performance amplifier module which is featured in this issue. This article includes photos of the final PCB design and if this is compared with the prototype PCB in the July & August issues, you will see that there are quite a lot more SMDs on the final version. That is because we have incorporated more features, something that we just could not have done if the PCB used only through-hole components; a much larger PCB would have been required. Perhaps the key added feature is the clipping indicator, which means that users will be able to avoid inadvertently driving the amplifier into clipping and audible distortion. So not only were we able to produce a PCB with much improved topology compared to the previous Mk3 version, as well as give it a smaller footprint, we were able to add desirable features which were simply not envisaged when the original design was produced quite a few months ago. I still find SMDs mind boggling compared to the equivalent through-hole components. But we have been through the same adjustment process in the past as new technology has been introduced. No doubt it will all happen again in the future. Leo Simpson siliconchip.com.au