Korg MS 20 f->Volt Converter

[Martin Czech]

> this idea is built into the electro-harmonix guitar/bass microsynth.  it contains
> two comparators that look for pos/neg absolute peaks respectively.  these
> comparators drive a s/r flip-flop giving a nice square-wave output ( but not
> necessarily 50/50 duty cycles ).  the tracking on the circuit was acceptable for
> single-string guitar stuff, but sometimes liked to oscillate between octaves as
> the note decayed.
> 

Yesterday I looked into the Moog P->V patent:

The main idea is to use a couple of half wave rectifieres.  The input
goes into a first RC highpass (DC reject), then goes into the first
HWR. That output is differentiated by a simple RC highpass. Then into
the next HWR and so on.  The patent shows three such stages. The first
HWR isolates say the negative wave portion. This is differentiated,
ie. the peaks are exagerated, and a new ac signal is formed, then comes
the next stage etc.  After the three stages the main peak of the input
signal should be isolated.  

It is a better idea to look for peaks then for zero crossings.

This is just imagination of the waves in my
head. Have to set up an simulation.


m.c.