[sdiy] PLL module

[Scott Gravenhorst]

"David G. Dixon" <dixon at interchange.ubc.ca> wrote:
>> I designed this PLL circuit for audio to track a FatMan VCO and produce
>> 1F, 1.5F, 2F, 3F,
>> 4F, 6F and 12F outputs.  Lag time is adjustable and can be made quite
>> insignificant at
>> the low end.
>> 
>> http://home1.gte.net/res0658s/fatman/4046pll.html
>
>That's a cool idea!  I was going to build an octave divider, but this seems
>much more useful.  I love this list!

Ah, well, an octave _divider_ is also useful as it drops a VCO output by an octave.  I've
also used the divide by 3 circuit to do - uh, divide by 3 which produces a perfect fifth
below the input frequency (actually I think it's an octave and a fifth below).

>I'm also working my way toward a saw animator "inspired" by Mark Barton's
>description of Cynthia's unit on her website.  For that, I was thinking of
>using Harry Bissell's (very cool) EFM pitch follower circuit, perhaps with
>one or two little changes.  I suppose it wouldn't be a big deal to adapt
>that circuit to this application?  The selling point would be that the lag
>of that circuit is exactly two periods of the incoming wave, irrespective of
>the frequency (and this can actually be reduced to one period if you're
>clever (I think)).

My circuit can work with input signals other than a VCO to some degree or other.  It
prefers a signal like a sawtooth VCO where the signal swing goes rail to rail from the
perspective of the 4046 IC.  It also works best with one zero crossing per cycle.

-- ScottG
________________________________________________________________________
-- Scott Gravenhorst
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