Silicon ChipAudio Mixing Cables - March 2025 SILICON CHIP
  1. Outer Front Cover
  2. Contents
  3. Publisher's Letter: Alipay & WeChat show us the way
  4. Feature: Prosthetic Limbs by Dr David Maddison, VK3DSM
  5. Subscriptions
  6. Project: Power LCR Tester, Part 1 by Phil Prosser
  7. Feature: The Power Grid’s Future, Part 1 by Brandon Speedie
  8. Project: Audio Mixing Cables by Julian Edgar
  9. Feature: Antenna Analysis, Part 2 by Roderick Wall, VK3YC
  10. Project: RF Remote Receiver by Tim Blythman
  11. Project: Continuity Tester by Tim Blythman
  12. Project: Versatile Waveform Generator by Randy Keenan
  13. Project: Shed Alarm by Julian Edgar
  14. Feature: Precision Electronics, Part 5 by Andrew Levido
  15. Project: Pico 2 Audio Analyser by Tim Blythman
  16. Feature: Transitioning to the RPi Pico 2 by Tim Blythman
  17. Serviceman's Log: The dishwasher that wouldn’t by Dave Thompson
  18. PartShop
  19. Vintage Radio: National R-70 Panapet by Ian Batty
  20. PartShop
  21. Market Centre
  22. Advertising Index
  23. Outer Back Cover

This is only a preview of the March 2025 issue of Silicon Chip.

You can view 49 of the 112 pages in the full issue, including the advertisments.

For full access, purchase the issue for $10.00 or subscribe for access to the latest issues.

Items relevant to "Power LCR Tester, Part 1":
  • Power LCR Meter PCB [04103251] (AUD $10.00)
  • PIC32MK0128MCA048 programmed for the Power LCR Meter [0410325A.HEX] (Programmed Microcontroller, AUD $20.00)
  • Software & STL files for the Power LCR Tester (Free)
  • Power LCR Meter PCB pattern (PDF download) [04103251] (Free)
  • Power LCR Meter panel artwork and drilling diagrams (Free)
Articles in this series:
  • Power LCR Tester, Part 1 (March 2025)
  • Power LCR Tester, Part 1 (March 2025)
  • Power LCR Meter, Part 2 (April 2025)
  • Power LCR Meter, Part 2 (April 2025)
Articles in this series:
  • The Power Grid’s Future, Part 1 (March 2025)
  • The Power Grid’s Future, Part 1 (March 2025)
  • The Power Grid’s Future, Part 2 (April 2025)
  • The Power Grid’s Future, Part 2 (April 2025)
Articles in this series:
  • Antenna Analysis, Part 1 (February 2025)
  • Antenna Analysis, Part 1 (February 2025)
  • Antenna Analysis, Part 2 (March 2025)
  • Antenna Analysis, Part 2 (March 2025)
  • Antenna Analysis, Part 3 (April 2025)
  • Antenna Analysis, Part 3 (April 2025)
Items relevant to "RF Remote Receiver":
  • Software for JMP022 - RF Remote Receiver (Free)
Articles in this series:
  • Wired Infrared Remote Extender (May 2024)
  • Symbol USB Keyboard (May 2024)
  • Wired Infrared Remote Extender (May 2024)
  • Thermal Fan Controller (May 2024)
  • Symbol USB Keyboard (May 2024)
  • Thermal Fan Controller (May 2024)
  • Self Toggling Relay (June 2024)
  • Self Toggling Relay (June 2024)
  • Arduino Clap Light (June 2024)
  • Arduino Clap Light (June 2024)
  • Lava Lamp Display (July 2024)
  • Digital Compass (July 2024)
  • Digital Compass (July 2024)
  • Lava Lamp Display (July 2024)
  • JMP009 - Stroboscope and Tachometer (August 2024)
  • JMP007 - Ultrasonic Garage Door Notifier (August 2024)
  • JMP009 - Stroboscope and Tachometer (August 2024)
  • JMP007 - Ultrasonic Garage Door Notifier (August 2024)
  • IR Helper (September 2024)
  • IR Helper (September 2024)
  • No-IC Colour Shifter (September 2024)
  • No-IC Colour Shifter (September 2024)
  • JMP012 - WiFi Relay Remote Control (October 2024)
  • JMP012 - WiFi Relay Remote Control (October 2024)
  • JMP015 - Analog Servo Gauge (October 2024)
  • JMP015 - Analog Servo Gauge (October 2024)
  • JMP013 - Digital spirit level (November 2024)
  • JMP013 - Digital spirit level (November 2024)
  • JMP014 - Analog pace clock & stopwatch (November 2024)
  • JMP014 - Analog pace clock & stopwatch (November 2024)
  • WiFi weather logger (December 2024)
  • Automatic night light (December 2024)
  • WiFi weather logger (December 2024)
  • Automatic night light (December 2024)
  • BIG LED clock (January 2025)
  • Gesture-controlled USB lamp (January 2025)
  • Gesture-controlled USB lamp (January 2025)
  • BIG LED clock (January 2025)
  • Transistor tester (February 2025)
  • Wireless flashing LEDs (February 2025)
  • Transistor tester (February 2025)
  • Wireless flashing LEDs (February 2025)
  • Continuity Tester (March 2025)
  • RF Remote Receiver (March 2025)
  • Continuity Tester (March 2025)
  • RF Remote Receiver (March 2025)
  • Discrete 555 timer (April 2025)
  • Weather monitor (April 2025)
  • Discrete 555 timer (April 2025)
  • Weather monitor (April 2025)
Articles in this series:
  • Wired Infrared Remote Extender (May 2024)
  • Symbol USB Keyboard (May 2024)
  • Wired Infrared Remote Extender (May 2024)
  • Thermal Fan Controller (May 2024)
  • Symbol USB Keyboard (May 2024)
  • Thermal Fan Controller (May 2024)
  • Self Toggling Relay (June 2024)
  • Self Toggling Relay (June 2024)
  • Arduino Clap Light (June 2024)
  • Arduino Clap Light (June 2024)
  • Lava Lamp Display (July 2024)
  • Digital Compass (July 2024)
  • Digital Compass (July 2024)
  • Lava Lamp Display (July 2024)
  • JMP009 - Stroboscope and Tachometer (August 2024)
  • JMP007 - Ultrasonic Garage Door Notifier (August 2024)
  • JMP009 - Stroboscope and Tachometer (August 2024)
  • JMP007 - Ultrasonic Garage Door Notifier (August 2024)
  • IR Helper (September 2024)
  • IR Helper (September 2024)
  • No-IC Colour Shifter (September 2024)
  • No-IC Colour Shifter (September 2024)
  • JMP012 - WiFi Relay Remote Control (October 2024)
  • JMP012 - WiFi Relay Remote Control (October 2024)
  • JMP015 - Analog Servo Gauge (October 2024)
  • JMP015 - Analog Servo Gauge (October 2024)
  • JMP013 - Digital spirit level (November 2024)
  • JMP013 - Digital spirit level (November 2024)
  • JMP014 - Analog pace clock & stopwatch (November 2024)
  • JMP014 - Analog pace clock & stopwatch (November 2024)
  • WiFi weather logger (December 2024)
  • Automatic night light (December 2024)
  • WiFi weather logger (December 2024)
  • Automatic night light (December 2024)
  • BIG LED clock (January 2025)
  • Gesture-controlled USB lamp (January 2025)
  • Gesture-controlled USB lamp (January 2025)
  • BIG LED clock (January 2025)
  • Transistor tester (February 2025)
  • Wireless flashing LEDs (February 2025)
  • Transistor tester (February 2025)
  • Wireless flashing LEDs (February 2025)
  • Continuity Tester (March 2025)
  • RF Remote Receiver (March 2025)
  • Continuity Tester (March 2025)
  • RF Remote Receiver (March 2025)
  • Discrete 555 timer (April 2025)
  • Weather monitor (April 2025)
  • Discrete 555 timer (April 2025)
  • Weather monitor (April 2025)
Items relevant to "Versatile Waveform Generator":
  • Versatile Waveform Generator PCB [04104251] (AUD $5.00)
  • Versatile Waveform Generator PCB pattern (PDF download) [04104251] (Free)
  • Front panel label and drilling template for the Versatile Waveform Generator (Panel Artwork, Free)
Articles in this series:
  • Precision Electronics, Part 1 (November 2024)
  • Precision Electronics, Part 1 (November 2024)
  • Precision Electronics, Part 2 (December 2024)
  • Precision Electronics, Part 2 (December 2024)
  • Precision Electronics, Part 3 (January 2025)
  • Precision Electronics, part one (January 2025)
  • Precision Electronics, part one (January 2025)
  • Precision Electronics, Part 3 (January 2025)
  • Precision Electronics, part two (February 2025)
  • Precision Electronics, Part 4 (February 2025)
  • Precision Electronics, Part 4 (February 2025)
  • Precision Electronics, part two (February 2025)
  • Precision Electronics, part three (March 2025)
  • Precision Electronics, part three (March 2025)
  • Precision Electronics, Part 5 (March 2025)
  • Precision Electronics, Part 5 (March 2025)
  • Precision Electronics, Part 6 (April 2025)
  • Precision Electronics, Part 6 (April 2025)
  • Precision Electronics, part four (April 2025)
  • Precision Electronics, part four (April 2025)
  • Precision Electronics, part five (May 2025)
  • Precision Electronics, Part 7: ADCs (May 2025)
  • Precision Electronics, part five (May 2025)
  • Precision Electronics, Part 7: ADCs (May 2025)
  • Precision Electronics, part six (June 2025)
  • Precision Electronics, part six (June 2025)
Items relevant to "Pico 2 Audio Analyser":
  • Pico (2) Audio Analyser PCB [04107231] (AUD $5.00)
  • 1.3-inch blue OLED with 4-pin I²C interface (Component, AUD $15.00)
  • 1.3-inch white OLED with 4-pin I²C interface (Component, AUD $15.00)
  • Short-form kit for the Pico 2 Audio Analyser (Component, AUD $50.00)
  • Pico Audio Analyser PCB pattern (PDF download) [04107231] (Free)
  • Pico 2 Audio Analyser firmware (0410723B) (Software, Free)
Articles in this series:
  • Pico Audio Analyser (November 2023)
  • Pico Audio Analyser (November 2023)
  • Pico 2 Audio Analyser (March 2025)
  • Pico 2 Audio Analyser (March 2025)
Items relevant to "Transitioning to the RPi Pico 2":
  • Software for the article on transitioning to the RPi Pico 2 (Free)

Purchase a printed copy of this issue for $13.00.

Audio Mixing Cables Simple Electronic Projects with Julian Edgar Add an extra input to an audio amplifier or mix the sounds from two sources with these easy do-ityourself mixing cables. I have installed two large subwoofers in my roof space, powered by a dedicated two-channel amplifier, that need to work with two different audio systems. One is my home hifi system, while the second is a home theatre system. I could use a line-level switch to connect the subwoofer amplifier to either the home theatre or hifi system, one at a time. However, since the subwoofer amplifier is located in the roof space, that would have made things a bit difficult without adding very long leads. But why not permanently connect both inputs to the amplifier via twointo-one Y cables? Well, I tried that and found it won’t work! The hifi and home theatre system outputs end up ‘fighting’ each other. John Clarke suggested a very simple solution: put together a couple of Y mixing cables. Here’s how I made them; it only takes a short time and costs little. To make a two-channel system for stereo, you will need (see Photo 1): • Some good-quality RCA leads (don’t use cheap ones – the conductors aren’t thick enough to work with). • Four 1kW ½W resistors. • A small piece of plain punched board (laminate). • Two small plastic boxes. Depending on how you mount the boards and cables, you may also need some PCB stakes, standoffs and grommets. Buy sufficient RCA cables to give you the correct number of plugs and sockets for your application. In my case, I needed two mixing cables, each with a male output and one male and one female input. We will now look at making one cable – each assembly is identical. Cut the leads so that you have three connectors and their associated cables. Once you have done this, carefully strip the outer insulation sheath from the end of each cable and then twist the braid (the outer copper sheath) strands together. With some cables, you will need to use a thin pointer to separate the strands of the braid first. When you are twisting the braid into a single wire, be very careful that every tiny strand of copper is twisted together, with no loose strands remaining that could cause short circuits. This twisted conductor is the ground Photo 1: these are all the parts required to build the Audio Mixing Cables for a two-channel amplifier system. Photo 2: the RCA leads should be cut as shown with the wires stripped. 46 Silicon Chip Australia's electronics magazine siliconchip.com.au connection. Strip a short length from the other wire – the signal connection – and then tin each conductor with solder (Photo 2). Next, solder the signal leads of each input cable to the resistors that then feed the single output. To give attachment points on the perforated board, push short lengths of stiff copper wire through the holes to form pins. You could use PCB stakes instead. Let’s now look at the board more closely (Photos 3 & 5). All the connections are visible – there is no wiring under the board. Solder the braided ground connection of each cable to a stake to physically secure it. The two signal inputs each connect to one end of a resistor, with the other ends of the resistors joined to the output signal. The ground connection between the joined input grounds and the output ground is made by the insulated black wire visible in the photos. Once the soldering is complete, the board can be mounted in a box. I already had these salvaged boxes; all I needed to add were some cable grommets through the existing U-shaped holes (Photo 4). You could use a lowcost Jiffy box or similar. Before you close the box up, do some testing with your multimeter. Every plug’s outer (ground) connection should have continuity (near zero resistance) to every other plug’s ground connection. The two input plugs should have 2kW resistance between their inner (signal) connections, and there should be 1kW resistance between each of the input signal connections and the signal connection of the output. Finally, there should not be continuity between any signal and ground connection. In addition to allowing two different inputs to operate a two-channel amplifier, as the name suggests, the cables also allow the two signals to be mixed (both input signals being heard simultaneously) if that is desired. For example, you could play music while watching TV and hear both if you used such a cable to merge the outputs of a CD/DVD/Blu-ray player and television. The signal level is reduced by half in the mixing cable. The resulting disadvantage is that the signal-to-noise ratio of the signal is a little poorer, but that is not so important for my subwoofer use case. And now, I don’t have to climb into the roof space to swap the inputs of the subwoofer amplifier! SC siliconchip.com.au Photo 3: the layout of the Audio Mixing Cables is very simple, so you can either wire it up as shown or choose your own way. Note that we don’t have any connections on the underside of the laminate. Photos 4 & 5: the finished project mounts neatly in a small plastic box. These boxes are around 5 × 7.5cm. Australia's electronics magazine March 2025  47