really trying to fully wrap my head around the filter envelope - a few questions

[gorilladunk]

Not sure if the rev2's filter envelope is much different from any other synth, but this is the only one I have so I'm asking here just in case...

I've had this synth for a few years and I have what I think is a pretty solid understanding of how DADSR envelopes work, but I do regularly run into situations when building a patch where the envelope knobs are not doing what I would expect them to do.  This made me think that I should spend some more time trying to make sure I fully grasp what's happening.  The rev2 manual and countless youtube ADSR videos do a fine job of explaining, but there's a few uncertainties I have that I haven't been able to find an answer for...

I'm pretty sure I grasp the basics here - delay = amount of time from key press to the attack stage, attack = time it takes for the filter to open between the end of the delay stage and the beginning of the decay stage, decay = time it takes for the filter to close between the end of the attack stage and the beginning of the sustain stage, sustain = the amount that the filter is open while they key is being held, release = amount of time the filter takes to close after the key is released.

I think this is pretty standard stuff, but that isn't enough info for me to fully grasp how to place these values because I'm probably an idiot lol.  Two things that I've gathered from just testing that aren't explicitly stated in the manual, is that the  cutoff knob appears to set the point at the beginning of the attack stage, and the envelope amount knob seems to set the point at the end of the attack stage.  If this is true, then can I assume that 0% on the sustain knob = the cutoff frequency, and 100% on the sustain knob = the env amount frequency?  Meaning, it's impossible to set a sustain value higher than the env amount frequency or lower than the cutoff frequency?

My main question though, is that there seems to be a noticeable amount of time between the attack stage ending and the decay stage beginning.

Sound example
https://files.catbox.moe/q2fqwy.mp3

Settings screenshot
https://i.imgur.com/kVfLjQD.png

That is a pretty noticeable amount of time, no?  There is a clear point where it seems like the filter has opened as much as it's going to, but then that value sustains for a pretty long amount of time before the decay starts to close the filter a bit.  Increasing the attack knob does increase this amount of time, so my only explanation I can think of is that the filter is actually still opening right up until the decay point, but in such a way that is inaudible to human ears, or something.  Is this true?  With these settings in the screenshot, the sustain knob seems to have no perceptible change anywhere from about 50% to 100%, so I guess that does seem to confirm this maybe.

My other less important question: delay, attack, decay, release, are all values of time.  How much time is 100% on these knobs?  Setting attack to 100% it seems to be about 20 seconds before it starts to decay, but I'm curious if this is stated anywhere or if this max amount of time gets effected by any other parameters.

Sorry for the novel, just wanted to make sure I explained myself correctly.  Thanks

[Autosynther]

The way I read manual and get result I expect is:
- as you said cutoff position is where attack starts
- but I do not read Amount as absolute, but sum of distance to fully open or closed depending on positive or negative
- and velocity is involved

I estimate Amount+Velocity/2 compared to 127 of that distance to open or close
- that is how far cutoff goes during attack time

Sustain level I see as absolute cutoff freqency plus key amount value
- manual says key amount 64 is one halfnote cutoff change each key step
- I think there is a table in a forum thread with tips on top of forum how this works

Decay time is from calculated attack level(cutoff) until it reaches as cutoff to sustain level

The release time is from sustain calculated level to fully closed or open filter dependent on amount polarity

I don't need exact numbers, maybe to use self oscillating filter you might.

Thinking like this it works for me. And you can start using recursive modulations on curves how envelopes move about.

You can even use recursive modulation on lfo:s to get more exponential or logarithmic from triangle waveform.
- I made a thread about how to get closer to sine a while ago with oscilloscope pics how it works at different settings

[OakBloodThree]

My other less important question: delay, attack, decay, release, are all values of time.  How much time is 100% on these knobs?  Setting attack to 100% it seems to be about 20 seconds before it starts to decay, but I'm curious if this is stated anywhere or if this max amount of time gets effected by any other parameters.

A few years ago, some users worked on reverse-engineering some of the parameters.

Here's a post about attack time: https://forum.sequential.com/index.php/topic,3203.msg35911.html#msg35911

Also, attack time can be modulated by anything through the modulation matrix. It can even modulate itself! Scroll down in the thread for a post about recursive envelope modulation.