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Practical Electronics Editorial offices Practical Electronics Electron Publishing Limited 1 Buckingham Road Brighton East Sussex BN1 3RA Tel 01273 777619 Mob 07973 518682 Fax 01202 843233 Email pe<at>electronpublishing.com Web www.electronpublishing.com Advertisement offices Practical Electronics Adverts Tel 01273 777619 1 Buckingham Road Mob 07973 518682 Brighton Email pe<at>electronpublishing.com East Sussex BN1 3RA Editor Matt Pulzer General Manager Louisa Pulzer Digital subscriptions Stewart Kearn Tel 01202 880299 Online Editor Alan Winstanley Web Systems Kris Thain Publisher Matt Pulzer Print subscriptions Practical Electronics Subscriptions PO Box 6337 Bournemouth BH1 9EH Tel 01202 087631 United Kingdom Email pesubs<at>selectps.com Technical enquiries We regret technical enquiries cannot be answered over the telephone. We are unable to offer any advice on the use, purchase, re air or odification o co ercial e ui ent or the incor oration or odification o designs u lished in the aga ine. e cannot provide data or answer queries on articles or projects that are ore than five years old. Questions about articles or projects should be sent to the editor by email: pe<at>electronpublishing.com Projects and circuits All reasonable precautions are taken to ensure that the advice and data given to readers is reliable. We cannot, however, guarantee it and we cannot accept legal responsibility for it. A number of projects and circuits published in Practical Electronics employ voltages that can be lethal. You should not build, test, modify or renovate any item of mains-powered equipment unless you fully understand the safety aspects involved and you use an RCD (GFCI) adaptor. Component supplies We do not supply electronic components or kits for building the projects featured, these can be supplied by advertisers. We advise readers to check that all parts are still available before commencing any project in a back-dated issue. Advertisements Although the proprietors and staff of Practical Electronics take reasonable precautions to protect the interests of readers by ensuring as ar as ractica le that advertise ents are ona fide the magazine and its publishers cannot give any undertakings in respect of statements or claims made by advertisers, whether these advertisements are printed as part of the magazine, or in inserts. The Publishers regret that under no circumstances will the magazine accept liability for non-receipt of goods ordered, or for late delivery, or for faults in manufacture. Volume 51. No. 9 September 2022 ISSN 2632 573X Editorial Digital preamp There are two things we know PE readers like – you ask for them regularly – Hi-Fi projects and coverage of digital control systems and techniques. So, it’s surprising how rarely we put these two topics together. This month, we buck that trend with the start of a two-month project that combines the fidelity of an analogue design with the flexibility of digital control and a touch-screen interface. It includes Baxandall tone controls and uses a Micromite BackPack, so despite being low in cost it is high in features. We think you’ll love it! The power of batteries… and a warning I wrote last month about the importance of the new generation of battery technologies and the related issue of correct charging. So, it is only right that this month Alan Winstanley reports on what can go wrong if a Li-ion battery is misused, or fails through poor design, overuse or damage. The resulting pyrotechnics can be spectacular for all the wrong reasons. Like many of you, I have a variety of DIY tools that run off a common battery system. The official branded versions of the rechargeable Li-ion batteries that power these tools are pricey, but it is becoming ever clearer that low-cost, third-party bargains could be a very foolish purchase. This is one area where it definitely pays to think in the long term and to ask yourself what am I really saving with cheap batteries, what am I risking and how would I put out a battery fire? Do you have a fire detector, fire blanket and a fire extinguisher? They aren’t expensive, but if you need one in a hurry there is no substitute. Web issues and solutions We have had a few web issues this summer and we really appreciate the patience of those of you who have been affected. The good news is the PDF subscription website has been completely rebuilt and now runs smoothly and safely. For digital subscribers there is more good news. When the PDF subscription system was launched it made sense to include digital security features, but 10 years on all they do is annoy legitimate purchasers and provide very little protection to the publisher. Therefore, we have removed the irritating watermarking and PDF password protection. Matt Pulzer Publisher Transmitters/bugs/telephone equipment We advise readers that certain items of radio transmitting and telephone equipment which may be advertised in our pages cannot be legally used in the UK. Readers should check the law e ore uying any trans itting or tele hone e ui ent as a fine confiscation o e ui ent and or i rison ent can result ro illegal use or ownership. The laws vary from country to country; readers should check local laws. Practical Electronics | September | 2022 7