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a new version of this project, but it will be some time before that comes to fruition. So we don’t think that should stop you from building the already-published design, which is still a great performer. Because of the shortages, we temporarily stopped selling the set of critical parts to build the CLASSiC DAC but have now reintroduced the parts set in our Online Shop (siliconchip.au/ Shop/20/1815). You would likely have trouble getting the microcontroller too, but we can supply them programmed from siliconchip.au/Shop/9/1850 Note that the SD card socket used in the original project is now unobtainable. We have redesigned the PCB to use a commonly available type from siliconchip.au/Shop/8/5655 Before ordering anything, go through the parts list and check that you can get everything we don’t sell. While you said you don’t plan to use it, the PCM2902E is available, although stocks are low (it isn’t part of our set). We have added the MIC391003.3WS LDO regulator to our parts set. While alternatives are available, it is the part tested in the design and found to work well. We chose it Advertising Index Altronics.................................23-26 Dave Thompson........................ 111 Digi-Key Electronics...................... 3 Emona Instruments.................. IBC Jaycar................. IFC, 10-11, 38-39, ................................. 57, 79, 99, 103 for its good ripple rejection. While more expensive, we agree that the LT1963AEST-3.3 should work well as an alternative. As for the TOSLINK sockets, they are definitely a problem. Unfortunately, Altronics have told us they will discontinue them, hence the lack of stock. The closest alternatives we are aware of are RS Components Cat 8051677 & 805-1680 or element14 Cat 2991612. They are all currently in stock. You will probably have to cut off the plastic posts as there are no matching holes in the PCB, but they also have solder pins to retain them, plus the rear panel, so we think they should be OK. I have a question about the headphone amplifier from the November 2005 issue of Silicon Chip (“Studio Series Stereo Headphone Amplifier”, siliconchip.au/Article/3231). That module was included in the Studio Series Preamplifier from July 2006, which I purchased as a kit from Altronics circa 2010 and constructed, except for the headphone amplifier part. Now I’m completing the headphone amplifier. The instructions supplied by Altronics say to apply heatsink compound to each output transistor and to avoid using insulating washers in mounting these to the heatsinks. However, the Altronics kit supplied Finding an article on a insulating washers for the output Frequency Switch transistors. Some time in the last 10 years or so, Which approach would you recyou published a project that used the ommend — washers or heatsink comLM2917 frequency/voltage conversion pound? (P. H., Warwick, Qld) chip as a frequency switch. Can you ● Since the heatsinks are separate tell me which issue the project was in and the transistors don’t require isoand whether the kit is still available? lation from them, the ideal mount(P. H., Gunnedah, NSW) ing method is just to use the heatsink ● You can find articles using the Word compound. That gives the best heat Search page on our site: siliconchip. transfer and will keep the transisau/Articles/WordSearch tors running at a lower temperature, Using that to search for projects which is safer. mentioning “LM2917”, you are most However, you can use insulating likely referring to the Frequency-­ washers instead. If the washers are Activated Switch For Cars (June 2007; silicone, thermal transfer compound siliconchip.au/Article/2261). It was is not required. If using mica washavailable as a Jaycar kit (KC5378) ers, thermal compound is needed on which is now discontinued. both sides of the mica sheets. InsulatThat project has been superseded ing bushes are not required in either by the Deluxe Frequency Switch (May case since the transistors do not have 2018; siliconchip.au/Article/11062), exposed metal tabs. SC Keith Rippon Kit Assembly....... 111 LD Electronics........................... 111 LEDsales................................... 111 Oatley Electronics..................... 111 Ocean Controls............................. 7 SC GPS Analog Clock............... 106 SC USB Cable Tester.................. 56 Silicon Chip Shop............ 108-109 Silicon Chip Subscriptions........ 67 The Loudspeaker Kit.com............ 9 Tronixlabs.................................. 111 Wagner Electronics................... 101 112 Silicon Chip Errata and Next Issue Microchip Technology.............OBC Mouser Electronics....................... 4 To insulate or not to insulate LC Meter Mk3, November 2022: (1) the initial release of the PCB has a short circuit between the top middle terminal of S2 and the track above it going to pin D10 of the Nano. This will not stop it from working but will reduce the accuracy of capacitor measurements above about 800pF. Run a sharp knife along the short circuit, taking care not to cut the track above, then verify that the short circuit is gone. (2) the 330pF capacitor shown in the circuit diagram and PCB overlay, and in the parts list, should be 470pF instead. Kits were correctly supplied with two 470pF capacitors and no 330pF capacitors. (3) switch S1 (not used by the provided firmware) is not connected the same way on the PCB as shown in the circuit diagram. Neither of the ‘NO’ and ‘NC’ contacts are connected to GND, and the 15kW pull-down resistor is connected between them. If constructors wish to modify the firmware to use this switch, one end would need to be connected to GND. (4) the supplied HEX file can be uploaded to the Arduino Nano using AVRDUDESS, with the Programmer set to “Arduino” and a baud rate of 57600. Next Issue: the February 2022 issue is due on sale in newsagents by Monday, January 30th. Expect postal delivery of subscription copies in Australia between January 27th and February 14th. Australia's electronics magazine siliconchip.com.au