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Advertising Index Altronics.........................loose insert Chemtools.................................... 75 Control Devices Pty Ltd.................. 5 Core Electronics............................. 9 Emona Instruments........................ 7 Enertel Pty Ltd............................. 11 Gless Audio................................ 103 Hammond Manufacturing............. 13 Harbuch Electronics..................... 13 Hare & Forbes.......................... OBC Ask SILICON CHIP . . . continued from page 103 than 12V; around 9V is ideal. This can be done with a zener diode. For example, if you leave D1/D2 as originally specified (1N5819) and add a 4.7V zener in series with the positive supply, with its anode to pin 2 of CON8 and its cathode to the battery positive terminal, IC2 should have a supply of around 8.7V. That will give a continuous power output of around 3W, compared to about 2W with a 12V supply. Note that you would need to use a 5W zener diode (eg, 1N5337) as it will dissipate about 1.8W when the amplifier is delivering maximum power. For a cheaper solution, you could try putting a 10-12Ω 5W resistor in series Notes & Errata Speedo Corrector Mk3, September 2013: there should be four 1µF capacitors in the parts list (not three) and the circuit should show a 1µF capacitor between pins 5 & 14 of IC1. The overlay diagram is correct. Micromite Microntroller, May 2014: a new version (Ver 4.5C) of MM­ Basic for the Micromite is available from the SILICON CHIP website. This version fixes a bug which could, in rare cases, cause the Micromite to partially erase its firmware and disable MMBasic when used with some low-cost USB-serial adapters. Other than that, no new functionality has been added. All but three chips we have supplied have the latest firmware version and those three customers have been notified. 104  Silicon Chip DOWNLOAD OUR CATALOG at High Profile Communications..... 103 www.iinet.net.au/~worcom Icom Australia................................ 8 WORLDWIDE ELECTRONIC COMPONENTS PO Box 631, Hillarys, WA 6923 Ph: (08) 9307 7305 Fax: (08) 9307 7309 Email: worcom<at>iinet.net.au Jaycar .............................. IFC,49-56 KCS Trade Pty Ltd........................ 21 Keith Rippon .............................. 103 KitStop.......................................... 75 with the supply. This will cause the supply voltage to drop as IC2 draws more current, reducing dissipation in IC2 at higher power settings. This may also drop the supply voltage by enough at idle to keep IC2 within its ratings with a 13.8V battery but you’d have to check it. LD Electronics............................ 103 Query on channel component matching Premier Batteries......................... 12 In your various stereo preamp/power amplifier kit designs, do the various kit suppliers go to the trouble of matching components (between channels) when deemed necessary (RIAA equalisation) for example? I’ve graphically learned this lesson in many of the stereo kits that I’ve personally built. Just the other day, I checked the value of the RIAA capacitors in the old Universal Preamplifier kit (SILICON CHIP, April 1994) that I’d built some years ago. The capacitor values as measured on my trusty (but reliable) capacitance meter were all over the place so I replaced them with matched sets of the correct values and it has made quite a beneficial difference in terms of equalisation accuracy and stereo image. I don’t recall this point ever being stressed and/or even mentioned in your construction articles. Perhaps in the interests of optimised performance, it should be. My capacitance meter is my most used and valuable LEDsales.................................... 103 Master Instruments...................... 93 Microchip Technology................... 79 Mikroelektronika......................... IBC Ocean Controls............................ 10 QualiEco Circuits Pty Ltd............. 59 Quest Electronics....................... 103 RFrepairs................................... 103 RF Modules................................ 104 Rohde & Schwarz.......................... 3 Sesame Electronics................... 103 Silicon Chip Binders..................... 48 Silicon Chip Online Shop........ 38-39 Silicon Chip Subscriptions........... 96 Silvertone Electronics.................. 61 Wiltronics........................................ 6 Worldwide Elect. Components... 104 bit of test gear for such projects. (F. S., Ingham, Qld). • Ideally the components in the feedback network (which sets the RIAA equalisation) should be 5% tolerance or better. Most capacitors with a nominal 10% tolerance can be expected to be within 5% (or better) SC of their nominal value. siliconchip.com.au