1968 SWTPC Theremin - looking for any info

Posted: 1/6/2025 3:33:09 PM
jsherm

Joined: 1/6/2025

Hello everyone, I'm a long time lurker and new member here. I just purchased an Etherwave Standard and a Lost Volts LV-4 as my first theremins. 

The reason I even got interested in the theremin is that my father recently gave me a theremin he was gifted by his sister's boyfriend in college. Here's the information I was able to gather about it from some research:

1968 SWTPC Theremin Kit
- Manufacturer: Southwest Technical Products Corporation (SWTPC), San Antonio, TX. 
- Connection: HemisFair '68 (World’s Fair), October 6, 1968. 
- Design: 
  - DIY kit with a wooden enclosure. 
  - 14.5” x 7” x 3”. 
  - Battery-powered (9V). 
  - 1/4-inch audio output for amplifier or speaker. 
  - Controls: Pitch knob, Volume knob, On/Off switch. 
- Circuitry: 
  - Analog design with inductors and discrete components. 
  - Red inductors (coils) for pitch/volume heterodyning. 
  - Minimalist design for hobbyist assembly. 
- Condition: 
  - Wooden case and components intact; minor wear. 
  - Likely needs restoration (e.g., replacing capacitors) for full functionality. 
- Significance: 
  - Rare collectible tied to the 1960s DIY electronics movement and theremin revival. 
  - Represents innovation showcased at HemisFair '68. 
- Value: Historical artifact or playable theremin after restoration. 

He still had the original box stored in his basement, and upon looking at it I can clearly see the address it came from:

Southwest Tech Prod Corp.
219 W. Rhapsody
San Antonio, Texas 76218

And that it either was purchased and/or came from the HemisFair '68 (World’s Fair), October 6, 1968.

I took photos of the theremin and the box it came in which you can see here: 1968 SWTPC Theremin

I'm curious if anyone has any information about this theremin besides the links I found online:

https://deramp.com/swtpc.com/History/SWTPC_History.htm

https://www.theremin.us/144/144.htm

https://en.wikipedia.org/wiki/HemisFair_'68

I plan on putting this theremin into a case and making sure to protect the box also as it adds the provenance to it.

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