This past weekend, I got to go to a flow-arts festival in Kentucky USA called PlayThink. This is my 3rd year, and it's always a blast. I had my synthesizer there, and allowed children and adults to play with it unsupervised without limit AND???? on the second day it broke. That's okay, I expected it to break much earlier, and also the malfunction is minor (power short, the power supplies just keep tripping).

    "Children, you say!??" Yes! PlayThink is a sober festival, family-friendly, people bring their whole families with children of all ages. I danced and danced and danced, some of the time with a six-month-old baby (wearing active-noise-cancelling over-ear hearing protection) who was on their mother's back. What's up Anna, it was great dancing with you and your tiny baby haha

    Hello Kitty Furiosa (my tin can synth in the picture) attracted lots of attention, even while broken. I got to pass out a bunch of 808 kick drum SynthCards (people love those!!!) and talk at length about the theory and practice of playing and building synthesizers.

    The back of my synth is a total chaos-nightmare of criss-crossing wires, using at least two color-code schemes. I'll snip it all off, and run straight, taught wires, three each of red, black, and green, and connect each module to the wires with the old split-insulation-wrap-wire-around-larger-wire-solder trick. I won't even need to put tape around the join since the taught wires will be holding everything in place. I will make a cardboard shield or something to keep patch cables from dangling and touching the power rails although even that would just make a POP noise if the patch cable were plugged in to anything, wouldn't hurt anything. Or trip the power supply, which would make a longer POP and erase whatever I was doing...

    ANYWAY, I'll pop a couple more pictures here of the festival. It was tons of fun, and I'm integrating the experience as well as one might expect.

This is my daughter Katrina. The hat, which she made, lights up.

NYQUISTNIGHTMARE finally done

     

Okay, the NyquistNightmare module is probably my most favorite module. It was born out of a desire to get AM radio-like noises out of a module, to introduce aliasing, combing, weird cross-modulations, all these weird noises into a signal. I have a tin-can module that's pretty rough but captures the essence. I have my first PCB version, which the low-pass VCF locks up sometimes for no reason I can understand, a version with an onboard MantisLadder VCF that doesn't lock up but sounds too smooth for my taste (and the SMD capacitors in the ladder were too small electronically but at least large enough to solder four film caps to their edges...

    But my new version WORKS! This one uses a MS-20 style filter for the low-pass, using the LM13700 as the variable resistor and the Darlington buffers as the ... buffers. Instead of René Schmitz's approach of using op amps as buffers, which is the MS-20 I build every single time I need a filter.

    The NyquistNightmare works like this: there's two voltage-controlled oscillators that can go from some low-ish frequency to way up high, maybe 80KHz, far above what we can hear. An audio signal frequency-modulates the frequency of the first VCO through an attenuator. The resulting modulated signal (oscillating so fast it'll usually be ultrasonic) frequency-modulates the second VCO.

    I'm not exactly sure how this works... I can kind of picture it, with two modulated signals cross-cancelling each other out, allowing the original signal to be sort of audible. With very careful adjustment of the four relevant knobs (two knobs attenuating the modulating signals, two knobs controlling the pitch of the carrier signal), you can get a reasonably good version of the original signal out.

    The cross-modulated signal can be extremely harsh, extremely rumbly, and very very quiet. So there's extra stuff in the signal chain. First there's a high-pass filter to quiet down the LIGHTNING THUNDER BOOOOM sounds that can come out of the first part. Then there's a low-pass filter to squelch the very piercing and constant squeal-whine.

    To address the extreme quiet part, I tossed in two "CinderBlock" circuits, which are auto-gain circuits that act like a really fast mostly not-noticeable compressors that can turn up very quiet signals. Two of those babies.

    Finally, there's an LED clipper part that is designed to limit the signal when there's giant voltage spikes. You know, to protect our ears.

    There's a wet/dry knob so you can hear what signal you're even putting into the module, and a effect volume knob... which on my prototype I switched, confusing me until I traced my error down on the PCB ha ha.

    I'm excited to have a version of this module that I'm happy with! It's one I'm going to have available to build at Knobcon 11 (early September of 2023). It's a rewarding module to play with, even when your input signal is a boring 220Hz sine wave. Something about the signal processing reminds me of what a rubber band does in one of those balsa stick airplane toys, where the rubber band will knot up. On the oscilloscope, the 220Hz sine will suddenly flip on itself, then sections will flip again, until the "knots" get closer and the smooth sine parts get shorter... and the sound is pretty neat. I made a TikTok demo real quick haha kids these days