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MARKET CENTRE Advertise your product or services here in Silicon Chip KIT ASSEMBLY & REPAIR FOR SALE PCB PRODUCTION DAVE THOMPSON (the Serviceman from Silicon Chip) is available to help you with kit assembly, project troubleshooting, general electronics and custom design work. No job too small. Based in Christchurch, New Zealand, but service available Australia/NZ wide. Email dave<at>davethompson.co.nz LEDsales PCB MANUFACTURE: single to multilayer. Bare board tested. One-offs to any quantity. 48 hour service. Artwork design. Excellent prices. Check out our specials: www.ldelectronics.com.au KEITH RIPPON KIT ASSEMBLY & REPAIR: * Australia & New Zealand; * Small production runs. Phone Keith: 0409 662 794 keith.rippon<at>gmail.com LEDS, BRAND NAME AND GENERIC LEDs, filament LEDs, LED drivers, heatsinks, power supplies, kits and modules, components, breadboards, hardware, magnets. Please visit www. ledsales.com.au Silicon Chip Binders REAL VALUE AT $21.50 PLU S P&P PMD WAY offers (almost) everything for the electronics enthusiast – with full warranty, technical support and free delivery worldwide. Visit pmdway.com to get started. Order online from www.siliconchip.com.au/ Shop/4 or call (02) 9939 3295. ADVERTISING IN MARKET CENTRE Classified Ad Rates: $32.00 for up to 20 words (punctuation not charged) plus $1.20 for each additional word. Display ads in Market Centre (minimum 2cm deep, maximum 10cm deep): $82.50 per column centimetre per insertion. All prices include GST. Closing date: 5 weeks prior to month of sale. To book, email the text to silicon<at>siliconchip.com.au and include your name, address & credit card details, or phone (02) 9939 3295. What modifications do I need to make? Could I use a 43-0-43V toroidal transformer? Do I need to change how I connect the amplifier module to the power supply module if I am using two transformers to power two channels? (W. L., Singapore) ● Taking your questions one at a time, sinewave power delivery is approximately V2 ÷ 4R, so for ±57V and 4W speakers, that’s 57V2 ÷ 16W = about 200W, or 100W for 8W. Assuming the 48V power supply you have mentioned supplies ±48V, with 4W speakers you will get 48V2 ÷ 16W = about 144W, or 72W into 8W. Make sure it’s a split supply; you can’t use a single-ended 48V DC supply to power a standard Class-AB amplifier. If it is ±48V, we don’t think any modifications would be required as that is close enough to the specified supply rails. siliconchip.com.au Regarding your second question on using a 43-0-43V toroidal transformer, it depends on the speaker impedance. We don’t recommend increasing the supply voltage for 4W speakers. For 6W or 8W speakers, a small supply voltage increase might be acceptable. Still, there are risks. Just a few volts can make a big difference to whether the amplifier is operating in the safe operating area (SOA) or not. We would expect ±61V DC rails with 43V secondaries on the transformer, although it could be a little higher depending on mains regulation, tolerances etc. Change all the MKTs to 100V rated (not hard to find) since the 63V ratings could be exceeded. You will need to replace the 100μF 63V electrolytic with an 80V or 100V type. Just make sure it will fit on the board. The small-signal transistors will be running close to their ratings – the Australia's electronics magazine BC546 and BC556 transistors are rated at 65V. They should be OK, but only just. If you want to up-rate them, we suggest switching to the KSC1845FTA (NPN) and KSC992 (PNP). We haven’t tested them, but they should give similar performance and they have 120V ratings. The bottom line is that if the speaker impedance is high enough, you could try it, but you will need to up-rate some of the parts (especially the capacitors) for safety. If you want to drive 4W speakers, you’re better off using a lower-­ voltage transformer (eg, 35-035V). You won’t lose much power and it’ll run cooler with much better margins. With each SC200 module powered via a single transformer and power supply module (that includes the bridge rectifier and filter capacitors), you would use the Fig.13 wiring diagram that is shown on page 79 of the July 2026  103