Shift Register Sequencer
My shift register sequencer is a clone of Music Thing Modular’s Turing Machine. It plays random sequences based on shifting binary values, but can be looped once you find one that you want to stick with.
The sequencer is based around two 4015 shift registers which are connected to a DAC0800 digital to analog converter. A knob on the front allows the user to select between looping the shift register, sending random inputs to the shift register, or looping andinverting the shift register. This allows you to either have random sequences play, or ‘lock’ them for a period of time so they don’t change. Another knob allows you to choose the sequence length of 2, 3, 4, 5, 6, 8, 12, and 16 steps.
The pulse output is tied to one of the shift register bits and goes high when that bit is high. This creates an irregular pulse signal which can be used to trigger gates.
This is a great module for generating pitch sequences, but it can also be clocked at audio frequencies allowing it to act as a very noisy and unpredictable oscillator.
Turing Machine Schematic (from Music Thing Modular)
| Name | Signal type | Notes | |
|---|---|---|---|
| In | CHNG CV | Control Voltage | Voltage control for whether the shift register repeats prior patterns or replaces them with randomness |
| In | CLOCK | Clock | Clock input |
| Out | PULSE | Clock | Outputs a clock signal when the first stage of the shift register is high |
| Out | NOISE | Noise | Noise output |
| Out | OUTPUT | Control Voltage | Outputs a voltage based on the first eight stages of the shift register |
