[sdiy] Good Expo curve for VCA use..

[Tom Wiltshire]

On 15 Oct 2012, at 20:38, Scott Nordlund wrote:

> (in analog envelopes it's generally an inverted decay up to a preset threshold, at which point it switches to the decay stage)

An example is the CEM3312, which charges to 6.5V, but has a 5V threshold for the end of the attack. This cuts off the long slow flat portion at the top of the capacitor's charging curve and tends to make the curve more linear. There are others, I'm sure.

I also agree with Scott's general point - although a exponential decay(expo2) sounds natural, an exponential attack(expo2) sounds a bit weird. Expo1, like a typical ADSR generator, is actually a more musical choice. YMMV, I guess.

It *is* definitely more difficult to evaluate attacks though. I once collected a pile of sound samples and wrote some code to perform a "best fit" of various attack curves (expo1, expo2, linear, cosine, etc) to the peak level between zeros for the rectified signal (a simplistic way to get the "envelope" of the sound"). The results were quite variable and not terribly convincing.

Tom