Monday, November 28, 2011

R/2R and VCO Usage in our Machines

We can make a large amount of sounds with the modules I have described so far, and love every minute of it. But there are some other modules worthy of your consideration: an R/2R ladder and a VCO or voltage controlled oscillator.

Think of the R/2R ladder as a simple digital to analog converter. You connect any number of outs from your gates, shift registers, and counters to the R/2R and that output will provide a voltage to send to your VCO. There is an order to the R/2R in which you have the Most Significant Bit all the way down to the Least Significant Bit. Playing with this order alters the output quite a bit.

Need a VCO? Take the easy way like I did and have something quite versatile: buy a couple of cd4046 ics.  The drawings below can be done on separate panels or on the same one.  You could get interesting results just taking the R/2R output straight to your mixer but running those voltages through the vco offers another variation on the sound.
Version 2.0

Notes:  Pin 3 and 14 are comparator and signal inputs.  These pins,when brought out to the panel, play a huge role in the variety of sounds this vco makes.  Pin 9 is where you will connect the output of your R/2R to.  The 10M resistor on pin 12 is what I had lying around.  You can experiment with other values if you like.  Same goes for the 22n;  experimentation is worth your time :).

Here's an audio sample

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