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

[Chris McDowell]

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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