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Notes & Errata Ultra-LD Mk.2 Amplifier Module, August & September 2008: in the printed version of the magazine, on page 71, the panel “Bullet-Proofing The Ultra-LD Mk.2” reads “Fortunately, this was relatively simple and involved adding a 22kΩ collector current-limiting resistor to Q9 (ie, this resistor is connected between Q9’s collector and ground).” This statement is incorrect. The resistor is, in fact, added between Q8’s collector and ground to limit the current through Q9, as shown in Fig.18 on page 70 of the same issue. Note that the panel has been removed from the on-line version as the circuit diagram in the August 2008 issue on the website already incorporates the changes mentioned in the print edition. Ask SILICON CHIP . . . continued from page 103 JBL Super Bullet Tweeters go down to around 3.5kHz (model 2402). The cabinets are still under construction. I have a 60W/channel class-A Amcron Power Line 3 stereo amplifier to drive the woofers. I also have a Cary Sixpac 50W/channel amplifier to drive the mid-range loudspeakers. It uses six EL34 tubes and is a Class-A monoblock. I intend to get a 12W/channel tube amplifier to drive the tweeters. Can you help? (F. J., via email.) • Since you are using separate amplifiers for each driver, you will need to use an active 3-way crossover. We can’t advise you on the exact design since we don’t have the details of the enclosure, the efficiencies of the vari- Advertising Index Touch-Screen Boat Computer With GPS, April 2016: version 3 (V3) software is now available for this project, with the following improvements: (1) Fixed a problem which may cause the BASIC program to repeatedly crash and restart if a point of interest (POI) is created with longitude and latitude set to 0° (the default). (2) Now allows over 50 points of interest (POI) to be created. In the main selection screen, you now use the PREV and NEXT buttons to take you through the list of POIs. (3) The heading indicator and POI direction indicator are now suppressed when the boat is stationary. (4) Improved rendering for the heading needle. (5) Removed the slash from the zero character in one of the fonts. ous drivers and the required cross­ over slopes (eg, 6dB/octave, 12dB/ octave etc). However, we did publish a 3-way active crossover design in the January 2003 issue which you may be able to adapt for your purposes. We can suggest our Currawong valve amplifier to drive the tweeters (October 2014 to March 2015): www.siliconchip. com.au/Issue/2014/October/Currawong+Stereo+Valve+Amplifier%3A SC +A+Preview Next Issue The July 2016 issue of is due on sale in newsagents by Thursday 23rd June. Expect postal delivery of subscription copies in Australia between June 23rd and July 7th. Allan Warren Electronics............ 103 Altronics.........................loose insert AV-Comm Pty Ltd........................... 7 Digi-Key Electronics.................. 3,25 DSCAPE.................................... 103 Emona Instruments.................... IBC Glyn Ltd NZ.................................. 14 Hammond Manufacturing............... 6 Hare & Forbes.......................... OBC High Profile Communications..... 103 Icom Australia.............................. 15 Jaycar .............................. IFC,49-56 Keith Rippon Kit Assembly ........ 103 LD Electronics............................ 103 LEDsales.................................... 103 Master Instruments........................ 9 Microchip Technology................... 17 Minitech Engineering................... 59 Mouser Electronics......................... 5 Ocean Controls............................ 16 Philips Monitors............................ 13 Rockby Electronics....................... 63 Rohde & Schwarz........................ 11 Sesame Electronics................... 103 SC Radio & Hobbies DVD............ 97 SC Online Shop............... 78-79,101 Silicon Chip Subscriptions........... 94 Silicon Chip Wallchart.................. 99 Silvertone Electronics.................... 8 Tronixlabs.............................. 10,103 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. 104  Silicon Chip siliconchip.com.au