[sdiy] filter cutoff and pitch manipulator idea involving joysticks

[Dave Magnuson]

>
>Yes, you want a quantizer. The Blacet Mini Wave is one solution 
>(<http://www.blacet.com/MW.html>www.blacet.com/MW.html). The PSIM-1 is 
>another (<http://www.synthmodules.com>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.

How about an LM3914 bar graph driver in dot mode?    That would take care 
of the comparators... each segment could connect to the pots like you 
mentioned above.

The 3914 has more outputs than you'd need (if you want only 5 pitches), but 
you could just make sure the joystick is only putting out enough voltage to 
trigger the 3914 up to the first 5 segments (So V+ fed to the joystick 
would need to be about half of the reference voltage fed to the 3914; that 
way the max voltage from the joystick will only activate up to the 5th LED 
output , rather than the last LED output)

One 3914, some pots, a few passive components and maybe a TL071 summing 
amp... pretty simple.   The page at national semi is here:
www.national.com/pf/LM/LM3914.html

The LEDs shown on the datasheet would be replaced by your voltage divider 
pots and a summing amp... and you need to make sure you treat the "mode" 
pin correctly to get dot mode, instead of bar mode

Dave Magnuson

PS... I've never abused the 3914 in this method... so I'm not 100% certain 
that the outputs will be consistent every time.  Anyone try something like 
this before?



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