[sdiy] filter cutoff and pitch manipulator idea involving joysticks

[john mahoney]

Yes, you want a quantizer. The Blacet Mini Wave is one solution (www.blacet.com/MW.html). The PSIM-1 is another (www.synthmodules.com). But this is Synth DIY, so...

Two solutions come quickly to mind:

1) The brute force method is to use a number of comparators and pots. The comparators can be adjusted to the range of travel that you want, which is kind of nice. You may or may not need some logic so that you only have 1 active output at a time. If you will set these once and leave them alone, then you don't -- but the output CV will be a summation of all the active outputs. Easier to picture in my head than to explain.

2) Another way is to use an ADC and a multiplexer (mux). The ADC converts the input CV to a digital control value, the top few few bits of which are used to address the mux. The mux has +5 or +10 volts at its input; each output of the mux runs through a tuning pot; those outputs are summed back together into one output CV. This isn't unlike a scaled down Mini Wave, so I guess that makes it a Micro Wave. (Sorry!!)
--
john


  ----- Original Message ----- 
  From: Milo Barrowclough 
  To: synth-diy at dropmix.xs4all.nl 
  Sent: Wednesday, October 13, 2004 4:29 PM
  Subject: [sdiy] filter cutoff and pitch manipulator idea involving joysticks


  hi everybody

  i am experimenting with computer joystick controllers, dismantling them and the like. i have discovered that both axes of the joystick controls a separate potentiometer i.e. one for x-axis one for y-axis . i think that the value is around 470k. i think it would be cool to modify the joystick so that one axis varies filter cutoff and the other axis varies pitch of an oscillator. hooking it up to control cutoff is simple enough, just tie one end of pot to supply voltage and the other end to vcf cv input. but pitch is more tricky. ideally i would like to have 4 or 5 pre-determined pitches, tuned to a certain key or scale, (i.e. 5 pots) , which are switched to vco cv input. which of the 5 pitches depends on the position on the value/position of the joystick pot. so in practice this would mean converting the varying voltage level from the pot into a fixed pitch (one of 5), which ever is closest. how could i do this?  
  i think that what i am looking for might be called a pitch quantizer.
  my skills are rudimentary, so it would have to be a fairly basic circuit.
  thanks


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