[sdiy] filter cutoff and pitch manipulator idea involving joy sticks

[Tim Parkhurst]

Quoth 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

********************************
One other possible solution comes to my little mind: How about using an
LM3915 bar graph chip? You run a voltage in, and you get 10 outputs that go
ON when the voltage is at a certain level (run it in "dot" mode). Each
output turns on a transistor, relay, or analog switch, and each of those is
hooked to a pot (allowing you to adjust the voltage for each step). Combine
the outputs of the 3915 with diode OR gates if you only want five steps.

Check the 3915 data sheet for allowable input levels (only up to 1 volt, I
think), and to get some application ideas.

And above, have fun with it!


Tim (voltage in, garbage out) Servo

*********************************
 
>----- 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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