[sdiy] "Timer Controlled VCO" (TCVCO) ?

[Neil Johnson]

Michael Zacherl wrote:

> I'm going through an awfully gibberish thread and found this post (without
> it stating the source of information):
> https://www.gearslutz.com/board/6535950-post313.html
>
> "It uses VCOs. The output frequency of the VCOs is measured digitally. The
> frequency data is used to adjust the control voltage of the VCOs. This is
> opposed to the design of DCOs: DCOs use digital timers to trigger the
> oscillator cycle directly while Schmidt uses a pure VCO path which is
> digitally observed. This is similar to the well known autotune procedure of
> classic synths - but the autotune is able to adjust the VCOs all the time(!)
> and does not need to be operated manually from time to time."
>
> So you're guess is probably right.
> Moreover all this modulation options hardly would be possible with DCO-ish
> designs, I'd say.

For that to work the autotune system needs to know when the VCO pitch
is being modulated.  Assuming those are also analogue I guess it must
carefully measure the pitch CV before, during, and after the frequency
measurement (even if doing a single-cycle reciprocal measurement) to
make sure it is not compensating for the wrong thing.

The classic autotune that the above text mentions takes over control
of the VCO so there are no artificial errors during the frequency
measurement.

Neil
-- 
--
http://www.njohnson.co.uk