[sdiy] Lin/Log VCAs and envelopes - compensating for log VCAs

[Synth Man]

Using pure digital envelope generators, I noticed this
linear-decay-to-sustain level "dead sound".. so I added an exponential
curve to blend the decay to the sustain on my own designs.. sounds
much better on a VCF too.

On Thu, Feb 11, 2016 at 10:59 AM, Simon Brouwer <simon.o at brousant.nl> wrote:
> Hi Tom,
>
> To my ears, linear slope envelope generators (as found in many digital
> synthesizers, as a linear slope is so much easier to calculate) are vastly
> inferior to exponential slope ones, as at the end of the decay phase the
> envelope does not gradually evolve into the sustain level, but switches from
> changing into static all at once. This often results in a sound that is
> interesting in the beginning, but loses all life in the sustain phase, or is
> cut off in an unnatural way. Layering and/or lots of reverb may mask this to
> an extent but that is just stopgap. Real synthesizers have curves!
>
> A linear decay combined with an exponential control/gain VCA will give an
> exponential decay of amplitude, but only if the sustain level is 0. With
> nonzero sustain levels the envelope will again switch from changing to
> static all at once.
>
>
> Best regards
> Simon
>
>> Op 11 februari 2016 om 15:47 schreef Tom Wiltshire
>> <tom at electricdruid.net>:
>>
>>
>> Yeah, I've done the same thing. My PIC VCADSR has linear or exponential
>> envelopes selectable. But that's not exactly what I'm suggesting here.
>>
>> Instead, I was thinking of doing a normal exponential ADSR for use with a
>> linear VCA, and a "log compensated" ADSR for use with a log VCA. This would
>> have a linear decay and release, but an extreme curve to the attack section
>> to give the typical shape even with the log VCA.
>>
>> Tom
>>
>> On 11 Feb 2016, at 09:14, Roman Sowa <modular at go2.pl> wrote:
>>
>> > It was too easy not to implement it, so I did that on my EG too. One
>> > switch determines exponential or almost-linear curve for attack and the
>> > other one for 1st decay. It simply changes the voltage charging the timing
>> > capacitor.
>> > Here's example scopeshot of both settings:
>> > http://www.sowa.synth.net/modular/addsr_punch.jpg
>> >
>> > Roman
>> >
>> > W dniu 2016-02-10 o 23:27, P Maddox pisze:
>> >> Tom,
>> >>
>> >> On 06/02/2016 19:08, Tom Wiltshire wrote:
>> >>> Being able to switch between the two curves would enable people to
>> >>> use either a log or linear VCA and still get the same effect.
>> >>>
>> >>> What do you all think?
>> >> That's what we do with 001/002/002R, you have the option for "linear"
>> >> or
>> >> "exponential" Envelopes.
>> >> Exponential "sound" quicker than linear but give the typical "synth"
>> >> sound.
>> >>
>> >> P
>> >>
>> >> _______________________________________________
>> >> Synth-diy mailing list
>> >> Synth-diy at dropmix.xs4all.nl
>> >> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>> >>
>> > _______________________________________________
>> > Synth-diy mailing list
>> > Synth-diy at dropmix.xs4all.nl
>> > http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>>
>> _______________________________________________
>> Synth-diy mailing list
>> Synth-diy at dropmix.xs4all.nl
>> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at dropmix.xs4all.nl
> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>