[sdiy] MORE Russian synth schematic...

[harrybissell]

I'm back...

I did a simulation of the VCF tuning oscillator.  It is NOT what I
expected...

It produces a fixed width pulse with a variable repetition rate.  This
rate could
easily drop into the audio range.

If the transmission gate IS a 4016... the polarity of thsi signal is
wrong IMHO.
The oscillator gives negative going pulses, which would make the switch
closed almost all the time.

Any experiences with this type of switched filter ??? I would have to
believe that
dropping the modulation into the audio range would be heard. OTOH this
is not
the most sophisticated synth design ever.  Clever... yes !

DD5 looks like a 4049 with wrong pinouts. This will do High to Low input
voltage
translation.  This IS the VCA.

H^) harry

harrybissell wrote:

> The CMOS gates in this synth would be "A" series imho...
> care should be taken in trying to retrofit the "B" (buffered)
> series.
>
> 4069 (always unbuffered) could be used in place of any simple
> inverters (or NAND wired as inverters)...
>
> This looks like a fun project.  I'll have to study it further
>
> H^) harry