Audio Projects
I'm not an audiophile. I enjoy music, but know friends that have an ear for sound that I just don't possess. They seem to be able to hear the difference between a good solid state amp and a good tube amp, and prefer the latter. I just enjoy working with hand-wired circuits, the kind that can be found in most early vacuum tube amplifiers, radios and other electronic equipment. I also enjoy a good challenge and learning new things, which these projects allow me to do.
Preamplifier
The stereo preamp pictured above is meant to go with the power amplifier that I will include here soon. The preamp uses two 12AU7s, and three 12Ax7s. The circuit is thanks to Wes Kinsler, and the schematic and explanation can be found here.
Theremin Project
For some unknow reason, a few years ago, I decided to make a theremin, a musical instrument used in the old scifi movies to create the wow-wow effects. The theremin is used by some musicans today, but they are reportedly very difficult to master. Since I have an interest in building vacuum tube projects, I searched for a tube theremin circuit. I found such a circuit online in the January 1961 Electronics Illustrated magazine.
The oscillator coils specified in the article (Miller 70-OSC) are no longer available (of course), so I used the P-C70-OSC coils from Antique Electronics Supply. However, these coils have no method of mounting. I was able to draw and 3D print mounts, and the .stl files for the mounts are here. They are the blue mounts on the theremin chassis on the two photos below.
Unfortunately, while the tone worked quite well by moving my hand around the tone antenna, the volume antenna circuit didn't work. I've dragged it off of the shelf several times to try and find the difficulty, but each time to no avail. Maybe next time.
