Sequencer for Analog Music Synthesizers


  • Up to 16 steps/voltages, each with its own LED
  • Each step can be enabled or skipped
  • Two basic step timing modes: 
  •      Individually adjustable step duration mode - each step lasts 1,2,4 or 8 time units
  • or:
  •      Individually adjustable step stutter mode - each step has 1,2,4 or 8 gate pulses
  • Gate and triggers for each step can be enabled/disabled
  • Moog-style S-trigger, or gate output as build options
  • Positive trigger pulse output also available
  • Selectable internal (adjustable rate) or external clock
  • Sequence can be triggered by external input or pushbutton switch
  • Sequences available: Up, Dn, Up/Dn, Random step, Random voltage
  • Selectable restart or stop at end of sequence
  • Two (equal) buffered voltage outputs, one with variable glide
  • Selectable output voltage range - 0 to 5.33V or 0 to 10.66V
  • Saved voltage values can be truncated to next lower equally-tempered value, or unconstrained
  • In tempered mode, voltage skips to next equally-tempered (1V/Oct) value when encoder is turned
  • Up to four sequences can be stored/recalled in non-volatile EEPROM
  • Requires single +12VDC 500 mA power supply

     One goal was to make the unit less expensive and easier to build by using a microcontroller and a 14-bit DAC together with a single encoder to make adjustments.  This also makes implementing new features and modes much easier,  since it's software instead of hardware.   There are still a lot of switches and LED's to wire up, as you can see in this picture of the underside:

     This is something that I am still fine-tuning and would like to get some other people to use and comment on.  I have two blank PC boards (3.8"x2.5"), identical to the one in the above photo (but blank), available for $30 each, which includes a programmed PIC chip and shipping to USA addresses.  Nothing else is provided, so you would need some kind of case, a 12VDC 500 mA AC adapter, a bunch of LED's, toggle switches, pushbutton switches and 1/4" jacks.  

Here are the schematics of the sequencer:

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Here is a recording made with my minimoog clone, using this sequencer.  It demonstrates the stutter feature.  The external control voltage is added to the keyboard voltage, so I was pressing keys to move the pitch up and down while feeding in a sequence that simply repeated.

DISCLAIMER: I take no responsibility whatsoever for the use and/or implementation thereof, or the misuse leading to damage to equipment, property, or life, caused by the above circuits.



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