+/- Mod env settings

S

Sequence2

Member
Could anyone here explain the process involved in using a +/- setting on the mod env while modulating the cutoff (probably the easiest effect to explain)
I understand how a positive setting would effect the cutoff frequency (the cutoff moves A-->D-->S-->R in an opening fashion)
But how does it work in a negative fashion? I read somewhere that it starts completely open and moves down the ADSR envelope (IE with a lengthy attack/ Decay, it will take a set amount of time until it goes from the highest cutoff point set to whatever the sustain is..?)
please correct me if I'm wrong.. been experimenting but I cant seem to completely grasp the concept
 
An ADSR generates a waveform over time. This waveform is by it's nature a positive going waveform only; there is no negative voltage/amplitude involved; it starts at 0 rises to the sustain amplitude level and falls to 0 on release.

+ in this context means positive going waveform is generated, as you say A/D\S-R\

- in this context means an inverted or negative going waveform is generated, as A\D/S-R/. It is also called the inverted ADSR. Of note is that the overall amplitude levels are still between 0 and the upper voltage level. In this case it starts at maximum voltage falls towards the sustain amplitude level and then rise to maximum on release.

You seem to understand this, but need to recognise that the overall time is invariant but the individual time-tracks are reversed.

So that what is a quick attack, quick decay and quick release in one ADSR setting when inverted becomes a slow attack, slow decay, slow release. When this inverted waveform is applied to the cutoff frequency, the cutoff frequency is affected not by time, but by voltage/amplitude level: the cutoff frequency follows the contour of the adsr waveform. the trick is to get the values to be what you require for the sound you are designing.

By yourself Welshs Synthesiser Cookbook to get a better understanding of all things to do with subtractive synthesis.
 
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