Some of us are guilty of picking up questionable hardware from garage sales, fleamarkets, and well-meaning relatives. There is a balance between turning down a good investment and hoarding, and if we figure out how to tell the difference you will be the first to know. [Clem Mayer] may start on the side of unwise acquisition, but he pushes a broken fetal detector into the realm of awesome by converting it to an analog synthesizer, born to headline at an Eastern European dance party.
He starts with a basic teardown, and we get to see how old hardware was serviceable with only two standard screws. It is a good thing too, because the nickel-cadmium batteries are older than some of you and they are in need of replacement. New nickel-metal hydride batteries got it up and running but [Clem] does not have a baby bump so its functionality turned to Pink Floyd era synthesizer circuit bending. Circuit bending involves modifying a circuit for sound it was not intended to make.
The exact circuit is never revealed because it is made and remade many times on the bench, but the gist is to start with the stock signal and treat it as a drum machine effect where 555 timers provide clock signals and sound synthesis, from there counters and switches establish a pattern, then some filtering, back to the timers and counters for chopping, and finally to an amplifier and out a speaker. Did you notice the lack of a microcontroller? We bet you did.
Even though this type of circuit hails from decades past, there is a message about using readily-available hardware. We learn that even if we cannot find an old fetal detector, the modern components and techniques will serve us the next time a “vintage” bit of hardware lands in the lab.
Once the circuit is in action we are treated to a couple of songs composed by our hacker, called Binary Dreams at 11:40 and Mental Spaghetti at 12:11. He is hardly the only composer in the neighborhood, check out Daphne Oram who wrote the book on electronic music and a guy who reads the book a little differently.
Via Element14 projects (membership required).