I finally received my copy of the November/December 2018 Nuts & Volts, following the interruption of mail service from a postal strike in Canada in December. I really enjoyed Robert Reed’s article on building a “Basic Audio Distortion Analyzer” on page 32. Had I seen it sooner I might well have built this project.
Like Mr. Reed, I have worked for different companies in the past who used professional quality audio distortion analyzers, such as those made in the 1970s by Hewlett Packard. In fact, at one point, I was responsible for the regular calibration of half a dozen of them (not sure of exact model numbers then, but likely the 331A or similar).
So, in December 2018, when I came across one of these vintage instruments at a reasonable price on eBay, I couldn’t help myself. I had to have it! (See the photo.)
Fortunately, all that was needed to get it up and running was to replace two shorted capacitors in the meter circuit and the neon pilot light with an LED. Fond memories indeed.
I was also pleasantly surprised when Mr. Reed described his use of the little known “Bubba” oscillator. The “Bubba” and other sine wave oscillators are well described in “Design of Op-Amp Sine Wave Oscillators” by Ron Mancini of Texas Instruments (www.ti.com/sc/docs/apps/msp/journal/aug2000/aug_07.pdf).
Don Dorward VA3DDN
First of all, congratulations on bringing out a fantastic publication.
Bryan Bergeron’s “Developing Perspectives” in the September/October issue was extremely informative.
Our trust is managing four schools and we are seriously thinking about bringing in a subject on DNA and Biotechnology. This article will definitely be an inspiration for our teachers.
We were seriously considering getting equipment from one company but found it required a huge investment. The companies Bergeron mentioned are comparatively reasonable and affordable.
Please continue writing articles on this subject.
Glad to hear the DIY Biotech articles are making a difference! We have several more planned, so stay tuned!