As you’d expect from someone who’s hobby’s include both audio/stereo and electronics, I try to measure and quantify things even when they are related to audio gear. While I will prefer to tune things by ear at the final step, measurement gives significant insight to some problems, in a very accurate way, in short amounts of time. One of the tools I would love to have for this is a very accurate audio analyzer, like one of the Audio-Precision offerings. What I’d like to have is the ability to measure parameters like harmonic distortion down to very low levels of distortion. However, most of these instruments are so expensive, even when bought used, that I gave up on finding a good one of these very long ago. Thankfully, nowadays, you can get very good results with much cheaper PC based gear. This post will describe one of the steps I’m taking to try and extend my ability to measure these parameters with my laptop, keeping in mind this is aimed at hobby use and must therefore be reasonably priced. I will start this post off with a bit of an introduction, but will dedicate most of it the the low THD oscillator and its power-supply.