Use simple components to make a pitch sequencer

Music Technology
Use simple components to make a pitch sequencer

Australian chiptunes wizard Sebastian Tomczak built this DIY 8-Step Waveform Editor using just a few integrated circuits (ICs) and slider potentiometers. Each slider represents the amplitude of a waveform at one step of its cycle, and since there are eight sliders, there are eight positions in the waveform. So, how does it work?


The waveform is made by switching quickly between the eight voltages set by the slide potentiometers, which are configured as voltage dividers. To do this, he started by generating a clock signal using a Schmitt trigger comparator in an astable oscillator configuration. The inverted output from the Schmitt trigger is connected to it’s input through an RC network, which causes it to flip back and forth, because whenever the output charges or discharges the capacitor, it causes the output of the Schmitt trigger to flip over, starting the cycle over again. The speed of this oscillation is controlled by adjusting potentiometer R1.

Next, this clock signal is fed into a 4040 ripple counter, which counts the clock cycles, and outputs the total number in binary. The lowest thee bits (representing numbers 0-7) are fed to an 4051n analog multiplexer chip, which uses that number to select the correct slider input, and connect it directly to the output. The result is that the voltage from each slider is connected to the output for one clock cycle, and if the clock is fast enough, it sounds like a wave. It’s a really simple way to create a complex sound!

Also, It’s hard to tell from the video, but the whole thing is pretty DIY- even the container that the potentiometers are mounted to is actually an upside-down plastic storage bin! He’s also modified the circuit a bit more to make a Periodic Waveform Editor via Hardware.

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