[sdiy] HPFs and ADSRs

[David G. Dixon]

Gee, this list has been kinda quiet lately...

When I visit Andre in Paris, I always learn something new.  This time, my
big revelation was just how important it is to have separate high-pass and
low-pass filters in series in order to achieve beautiful vintage synthesizer
sounds.  This I learned while playing with Andre's Korg MS-20.  Setting the
HPF resonance high while sweeping both cutoff frequencies with the same
envelope seems to be the secret to achieving some very nice sounds.

I also learned how annoying it would be to have only one envelope for
modulating both the VCF and the VCA, again from the MS-20.

After I finish my preamp/envelope follower, I guess my next project will
have to be a couple of SVFs and a couple of ADSRs.

Speaking of ADSRs, I've been studying the Envylope schematic (which I'm
beginning to understand, with difficulty).  If anyone here has any
experience with this circuit, I'd love to hear it -- I'm a little dubious
about some bits of it.  I've built a custom dual MFOS ADSR module (with
added AR repeat mode circuits and inverted outputs) which is a rock-solid
performer, but I need more ADSRs (ideally, one for each VCF and VCA) and I'm
thinking that my next ones should have some voltage control.  I'd also like
to add a delay.

Isn't it time we had another envelope thread?