[sdiy] VCO comparator's reference voltage - rail OK?

[cheater cheater]

Aye, that's true. Thanks for bringing this up.

On Mon, Mar 29, 2021 at 1:16 AM Chris McDowell <declareupdate at gmail.com> wrote:
>
> I think the point is that it doesn't matter so much where precisely that trip point is, only that it doesn't move. I personally don't pay for the higher precision.
>
> Cheers,
> Chris
>
> > On Mar 28, 2021, at 5:58 PM, cheater cheater via Synth-diy <synth-diy at synth-diy.org> wrote:
> >
> > The frequency of your VCO is inverse-linearly dependent on the trip
> > point of the comparator. Half the trip point = 2x the frequency. 1%
> > less trip point means pretty much 1% higher frequency, or 17 cents
> > higher.
> >
> > On Mon, Mar 29, 2021 at 12:03 AM Neil Harper via Synth-diy
> > <synth-diy at synth-diy.org> wrote:
> >>
> >>
> >>
> >> On 3/28/21 5:47 PM, cheater cheater via Synth-diy wrote:
> >>> On Sun, Mar 28, 2021 at 10:50 PM Neil Harper via Synth-diy
> >>> <synth-diy at synth-diy.org> wrote:
> >>>>
> >>>> i have a drawer full of LM431's so i'll use that unless there's a reason
> >>>> not to?
> >>>
> >>> You don't want an adjustable voltage reference, you want a precision
> >>> constant voltage reference. Your adjustable voltage ref will be only
> >>> as good as the resistors you have. So unless you have 0.01%
> >>> resistors*, in the exact specific values that you need to get the
> >>> voltage you need, you're out of luck.
> >>>
> >>> *needed for 1 cent frequency accuracy
> >>
> >> i appreciate the reply cheater, but in this case the lm431 is just
> >> setting the trip points of the comparator and have no need for .01%
> >> accuracy here - just stability with unstable rail voltages.
> >>
> >>
> >> --
> >> /// Neil Harper
> >> /// Every Wave is New Until it Breaks
> >>
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