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Notes & Errata Appliance Earth Leakage Tester, May 2015: the parts list includes one 100nF MKT capacitor but two are required. Ultra-LD Mk.4 Power Amplifier Module, July-September 2015: the parts list on page 38 of the August 2015 issue gave an incorrect part number for the 4.7V zener diodes. It Ask SILICON CHIP . . . continued from page 95 switch-boxes, built with the best quality audio quality components. Do you know where a switch-box anything like this is available? Alternatively, where I can get suitable parts to build one (I haven’t been able to find a good 4-way switches, for phono use in particular)? Ideally I’d like a 4-outlet switch-box but anything with at least two outlets would be acceptable. The only option I’ve been able to find so far is to use a different headphone amplifier (made by Musical Fidelity) which has dual phono outlets (non-switchable) but could do the job if I’m willing to spend some money (either $350 or $900) to downgrade the quality of my headphone amplification by using it. If I can’t buy something like this or get it built anywhere, where is an electronics shop that could custom design and build it for me? Could consider having 10-100 of them made and reselling them though headphone shops if need be, if I can’t get just two. I hope you can point me in a good direction. (G. C., via email). •  We published a Two-Way Stereo Headphone Adaptor in the April 2008 Advertising Index should be BZX84B4V7-7-FDICT-ND. The ferrite bead type isn’t critical but we suggest Digi-Key 240-2548-1-ND. Altronics.........................loose insert 9-Channel IR Remote Control Receiver (September 2015): a bug in the receiver code could cause the last used function to be repeated in the presence of interference. The revised code 1510815B.hex fixes this. Hammond Manufacturing............. 13 Control Devices Group................. 15 Emona Instruments........................ 7 Hare & Forbes............................. 2-3 Icom Australia................................ 8 Jaycar .............................. IFC,45-52 KCS Trade Pty Ltd...................... IBC Keith Rippon ................................ 95 issue which can switch between two sets of headphones. However, the fact that there are resistors and pots in the signal path, with no buffering, means that it would not meet the high standards for distortion set by the Studio Series Headphone Amplifier (SILICON CHIP, November 2005) and more particularly, by the much higher performance headphone amplifier described in the September & October 2011 issues. With your existing set-up, all you really need are three 12V DPDT relays wired up to a rotary switch (or similar) such that the coils are energised to connect the input socket to one of the four output sockets. It can be totally passive and as long as the wiring is kept short and the whole thing is housed in an earthed metal case, it will have negligible effect on sound quality. After all, we pass hundreds of watts from a power amplifier through a 10A DPDT relay in our speaker protector module with virtually no measurable effect on sound quality. At the much lower voltage/current/ power levels for driving headphones, and given the higher load impedances, as long as good quality relays are used SC it should be fine. LD Electronics.............................. 95 LEDsales...................................... 95 Master Instruments.................. OBC Microchip Technology................... 11 Ocean Controls............................ 61 Radio & Hobbies DVD.................. 44 Rohde & Schwarz.......................... 5 Sesame Electronics..................... 95 Silicon Chip Binders..................... 87 Silicon Chip Online Shop........ 88-89 Silicon Chip Subscriptions........... 90 Silvertone Electronics.................. 12 Splat Controls................................. 9 Tendzone...................................... 10 Tronixlabs................................ 13,95 Next Issue The December 2015 issue of SILICON CHIP is due on sale in newsagents by Thursday 26th November. Expect postal delivery of subscription copies in Australia between November 25th and December 7th. WARNING! SILICON CHIP magazine regularly describes projects which employ a mains power supply or produce high voltage. All such projects should be considered dangerous or even lethal if not used safely. Readers are warned that high voltage wiring should be carried out according to the instructions in the articles. When working on these projects use extreme care to ensure that you do not accidentally come into contact with mains AC voltages or high voltage DC. If you are not confident about working with projects employing mains voltages or other high voltages, you are advised not to attempt work on them. Silicon Chip Publications Pty Ltd disclaims any liability for damages should anyone be killed or injured while working on a project or circuit described in any issue of SILICON CHIP magazine. Devices or circuits described in SILICON CHIP may be covered by patents. SILICON CHIP disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. SILICON CHIP also disclaims any liability for projects which are used in such a way as to infringe relevant government regulations and by-laws. Advertisers are warned that they are responsible for the content of all advertisements and that they must conform to the Competition & Consumer Act 2010 or as subsequently amended and to any governmental regulations which are applicable. 96  Silicon Chip siliconchip.com.au