Yeti Rambles

Ever on the lookout for new test gear to add to my collection I stumbled across the XR2206-based function generator. These can be bought as a kit pretty cheaply from AliExpress or from eBay, they're easy to put together and use offering 1Hz - 1MHz of range through the use of some jumpers. It has two output terminals, one that gives a square wave and one that gives either a triangle or sine wave, depending on the position of a jumper. The heart of the device is an XR2206 which is an "obsolete" function generator chip with some pretty good specs and a low external parts count.   I bought one of these kits because my ultra low THD sine generator (a Wien Bridge oscillator with a bulb) is fixed at ~1kHz and being able to steep the frequency (and use other waveforms) is a huge help in analysing a circuit  My Ultra Low THD Oscillator After building the kit I fired up Arta to measure the THD, the results were... disappointing, 2.7% if you set the amplitude right but around 4-5% m

This is just a short post to explain the concept of an audio probe and the design I went with for mine An audio probe is a common device in audio electronics which allows you to poke at a circuit and listen to the signal at that point, this lets you work through the signal path and pinpoint any faults  While you could just connect a lead to an amplifier and poke the signal you risk damage to the amp with any DC that might be present at that point. While a lot of amps have an input cap which will block the DC it shouldn't be relied upon, for this reason we need to add our own cap As you can see from the picture below the construction of an audio probe is pretty simple, I have a standard audio jack with a ground clamp which stays connected to the ground of the signal, I then have a 100nF capacitor going to a banana jack that lets me connect a regular multimeter probe.  Some people take apart a lead or use the leg of the capacitor itself for probing but I've found that cumbersome

The Problem  I have built and bough quite a number of guitar pedals now and not only is my main pedalboard out of room, my power supply (Harley Benton PowerPlant Jr.) is at capacity. Rather than build a bigger pedalboard and upgrade my supply it made more sense to me to create a new, separate, board to take some pedals off my main one. Not only will this mean I don't have to spend any money it will also allow me to be more focused with the sound for each board so I don't have the "Jack of all Trades Master of None" board I currently do.  Now the obvious problem with this idea is that I have no way to power this second board, enter the DIY Power Supply. The Electronics There are a number of ways to create a DIY PSU be it a fully linear or fully switching design, or even a mix of the two. A decision also has to be made about where the PSU will draw it's power from, will it plug directly into the mains or be powered from a lower voltage source?  Luckily for me I had