[sdiy] Modified Juergen Haible's VC-ADSR and mono synths ADSR behaviour.

[JH.]

> I build the Jurgen's schematic too but, in my prototipe if I apply short
> gate pulses with release set at maximum, the
> output voltage raise up the saturation of the op-amp U9D. My suspect is
> around the reset pulse applied on Q5 base
> and the servo loop that "compares" current  from R3 and R42.
> Opinions are welcome!

I never run into such a problem. Have you built it with exactly the same
components?
How short were the pulses, and how fast were they repeated?

>
> And now a question:
> I've ever thought that in an ADSR for a monophonic synth the attack
> phase must to start always from 0V each time
> the gate goes high, so some circuitry is needed in order to reset the
> release phase if still pending.
> But all the schematics I found don't work in this way: each time i press
> a key the attak phase begins were the release
> phase ends. The CEM3310 behaves the same.
>
> Well, how behaves the perfect ADSR for a mono synth ? With or without
> the release reset when a key is pressed ?

It's "perfect" if it behaves the way you like it!
I think the two major traditional ways are retriggerring the envelope, and
not retriggering th eenvelope at legato playing. Both don't reset the level
to
zero. I like it that way, especially as a combination of Release time and
your playing style (gap between two notes) allows some control over the
dynamics without any velocity sensing of the keyboard. Just release the
previous note a little earlier, and your starting level for the new note has
dropped a little lower. And vice versa.

Generally I would consider a full reset "unnatural" sounding - but this
means it may be
well worth to try it for exactly this special effect.

JH.