Below is a running list of mishaps, mistakes and synthesizers I have built with pictures and descriptions. I am not an electrical engineer, I am an artist.
Some of these circuits have been built using PCBs, others have been built completely from scratch based off various schematics found in books and on the internet.
If you have not yet set aside the time, money and energy to build circuits, I can tell you mistakes will be made and sometimes your project will not work much to your discouragement. But after perhaps countless 'failures,' when you finally recollect yourself, clean up your work area, and get your project to finally function, at least in some capacity, [usually because of some simple oversight, i.e. battery not connected], you may be rewarded with oh such scattered sweet sounding unpredictable waveforms that a computer would find difficult to create [no offense to those max/msp / pd / reaktor / bidule / csound / supercollider gurus among you, I strive to learn and create in such mediums just as much as in the circuit realm].
The Weird Sound Generator
The Weird Sound Generator was the first synthesizer I ever built. It was built on a printed circuit board of a circuit from Music from Outer Space designed by Ray Wilson. It operates off of a 40106 Hex inverter IC and has six oscillators that, depending on the switching configuration, can modulate each other or can all be summed together. Everything passes through an active low pass filter with course and fine frequency cutoff and resonance potentiometers. After the circuit was built I thought it would be nice to incorporate more touch into the controlling of the synth. After finding some bend points that I found interesting, I soldered them to some thumbtacks. The enclosure is an old first aid kit. A simple and fun project.
The Snake Box
The Snake Box was my first attempt to build a semi faux-modular synthesizer [multiple circuits but no utilization of control voltages, with the exception of bend points on several of the oscillators]. The three circuits are based on The Cacophonator designed by Arthur Theremin [left], The Fuzzy Dicer [center] and The Low Rider [right], both of which can be found "Handmade Electronic Music" by Nicholas Colins. All circuits have bypass switches on their input and output buffering capacitors to allow for unpredictable outcomes when they are bombarded by DC. I decided to use RCA jacks instead of the popular banana jacks because they are cheaper and more abundant, patch cords can be made easily from scratch or from RCA cables found in the trash and because they exude a certain universal accessibility [a PEOPLE'S connector...]. Everything has been done to encourage bleed through. All LEDs are transistor driven, switchable on and off, and run off a separate battery to indicate positive waveforms / DC surges due to mods made to the schematic. Circuits were built in sequence from right to left and all operate off of their own 9 volt battery with a large capacitor [>2000 μF] in parallel with the main load so that when the battery is switched off, they all possess unique discharging characteristics.
The Cacophonator is a chaotic poly-oscillitic circuit that uses a 40106 hex inverter IC. The controls include an in-line potentiometer between the battery and the circuit to adjust current, affecting the range of sound from quiet rhythmic blips and pops to full on convulsive modulated tones. The circuit consists of four main in-line oscillators and two LFO's that modulate them. I included switches for each oscillator to switch between/add varying capacitance which affect the frequency range and discharge characteristic/waveform of each inverter. Bend points via steel nails can be connected with alligator clips or touch.
The Fuzzy Dicer is a distortion / gated oscillator circuit that uses 4093 NAND gate and 4049 hex inverter IC's. The input is boosted with a LM386 amplifier chip to allow for very low level signals to be used to trigger the circuit. I used three stages of inverters with switchable capacitors to alter oscillation range that goes into two in-line NAND gates. I also added an in-line current potentiometer to give it a more dynamic [and consequentially an unpredictably frightening] character. The input to the circuit is a connected to a pan pot taken from an old 8-track player that is connected to two RCA connectors. Transistor driven LEDs indicate positive peaks in the inverter and gate stages. The two outputs on the bottom consist one after a single NAND gate and the other after both NAND gates in-line.
The Low Rider is a distortion / frequency divider circuit using 4040 binary counter and 4049 hex inverter IC's. The inverter stages are the same as with The Fuzzy Dicer but instead the signal is connected to the clock and reset pins of the 4040, which has twelve outputs of exponential division values [the signal input functions as the clock speed, the outputs are multiple sub-octaves on each pin]. I included two LM 386 IC's, one before the inverters, the other before the 4040 to boost quieter signals, also allowing for interesting cutting in and out of division mode when a signal is amplified so much the chip seems to sense it as DC. The three inputs are situated as two being before the in-line inverter stages and one directly into the 4040 clock pin. I again used a current feeding potentiometer. I selected eight of the twelve outputs of the 4040 IC and each can be turned on-off and signal be adjusted.
The NAND Speaker
The Nand Speaker is another faux modular synth I built consisting of three circuits: Gated NAND Drone Synth by 9volts, Hysteresis Oscillator originally printed in Everyday Practical Electronics and the active low pass filter portion of The Weird Sound Generator by Ray Wilson of Music from Outer Space. Again, LEDs are transistor driven to indicate positive peaks of waveforms. The enclosure is an older 'school house' style intercom speaker box with 1/8" plexiglass as the control surface. The bottom is left open to allow for quick servicing/modification.
The Gated NAND Drone Synth operates off of four 555 timer IC's set up as pulse generators which act as gates 4093 IC's four oscillators. Each 555 pulse and NAND oscillator frequency is controllable, and each oscillator is has an on off switch and volume potentiometer. An in-line current potentiometer allows a slowl transition between quiet DC popping sounds to full on blithering bloops and solid buzzing tones.
The Hysteresis Oscillator circuit is a very simple full on-off amplitude modulator circuit that works off of a single 555 timer IC. It can barely go into auditory range (ie a ring modulator) and serves more as a very fast tremolo. I have added a switchable on-off wet-dry pot as well as switchable capacitors affecting the range of the modulating frequency. An LED indicates pulse rate.
The low pass filter circuit is based on Ray Wilson's lpf The Weird Sound Generator. It has course and fine frequency cutoff and resonance potentiometers. I modified it by adding a few more parallel connections to allow it to enter into self-oscillation as well as an added switch to change between low pass and high pass modes. An in-line current potentiometer affects mainly the resonance of the circuit but also the overall frequency response.