I've been working on mine recently. I found I need to use 6VDC on the heaters to eliminate hum. It uses a spring reverb tank with the sound on an ultrasonic carrier and was used in a Baldwin organ. I made some videos here:
https://www.youtube.com/watch?v=JTjV3-1uIsU
https://www.youtube.com/watch?v=obLCukUvvqA
https://www.youtube.com/watch?v=t7fcFqqaltE
schematics
Ultrasonic Reverberator from Electronic Musical Instruments Chapter 7 by R. H. Dorf.
https://od.lk/s/OV8yNDM5MjQ2OTFf/UltrasonicReverberator.pdf
https://od.lk/s/OV8yNDQ2MjIxNjVf/BaldwinPanoramic-1.pdf
https://patents.google.com/patent/US3136853
Similar sounds here:
Gumby on the Moon
https://www.youtube.com/watch?v=eJDJ1ALa9Eo
Accutronics BTDR-2H long decay reverb module for Theremin
https://www.youtube.com/watch?v=2aOym67frc8
Last edited: Jan 02, 2025 15:55:25