[sdiy] Basic VCO and Noise Source

patchell patchell at silcom.com
Wed Feb 26 16:04:43 CET 2003


    Lewis Bupp wrote:

> I am in search of a very basic VCO circuit. Precise keyboard tracking is not
> that critical, so long as it is stable if I apply a constant control voltage
> to it.
>

    If you want basic, the ASM1 VCO is about as basic as you can get.  Although,
your list of requirements are a bit thin, even with the ASM1 VCO, you can
eliminate things like the PWM to make it even more basic.

>
>
> I am also looking for a basic noise source.

    Do you want analog, or a shift register based noise?  If you want analog
noise, again, the ASM1 noise source is about as basic as you can get.

    If you want a shift register based noise source,
http://www.silcom.com/~patchell/synthmodulesII/200-1021.pdf

    can be simplified quite a bit by taking the last bit in the shift register
and putting a low pass filter on it, and increasing the clock rate a bit (1MHz
should do it)....rather than using the DAC like I plan (this circuit has not
been tested yet).

>
>
> Anyone have any suggestions?
>
> Lew
>
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--
 -Jim
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