I've been looking at a lot of Buchla modular vids over the last couple of days and there are some sounds there that I'm totally blown away by.

I'm really interested in emulating two aspects of that sound. First I'd like to emulate the vactrol envelopes' response that gives you those lovely woody thunks when you feed them with a pulse. Also, the complex oscillator gives out some amazing sounds.

Now I'm guessing that vactrol response might be easy-ish to model - it'd just be a matter of enveloping with a lookup, or a formula that gives a curve like a vactrol but I've not been able to find details of the buchla vactrol's response to a pulse - any ideas?

And any ideas of what kind of waveshaping fun is going on with the timbre knob on the complex osc? It has to be digital - it gives out foldover artifacts- so it should be do-able, but I've been playing with waveshaping and not really getting the same kind of sounds.

Any tips/ resources?

THis kinda thing is a good example -

If anyone else is interested in this kind of thing I've gathered that supersampling the waveshaper will help with the complex oscillator tone.

And apparently a lp filter on the envelope will help with the vactrol imitation. I'll post an example if I get anything nice.

What do you mean by supersampling? I don't think I've heard that term before.

And please do post what you come up with. I'd be very interested in what you find. I don't know anything about vactrol envelopes (a google search puts this thread as the number one hit!), but I do tend to send my envelopes through lowpass filters, especially drum sounds. It's a nice way to get more natural sounding shapes, particularly attacks.

yes, this thread came up for me on google too.

vactrol will be very easy to model in pd, we just need to find out how they work.

I would also be interested if you come up with anything.

@Maelstorm said:

I do tend to send my envelopes through lowpass filters, especially drum sounds. It's a nice way to get more natural sounding shapes, particularly attacks.

This is so simple, but I don't think it ever occurred to me. I'll have to try it!

Supersampling - do the waveshaping in a subpatch with sample rate 2x/4x etc. the patch's sample rate. Then in that subpatch apply a low pass filter a that rolls off up to the nyquist frequency. It cuts down on the rollover artefacts and improves sound quality considerably for complex/ non bandlimited timbres.
I think it's demonstrated in one of the PD example patches.

Not had a chance to play with this properly yet, but I'll post examples when I do. I've just been mucking about with waveshaping. Got a bit sidetracked by it.
Cross phase modulation of the channels of a stereo signal gives some cool effects, and a chebychev shaper just before a LP filter is nice.

I'd not really bothered with the PD waveshaping examples before, but there's bags of sonic fun there.

From what I've heard, the VTL5C3 and VTL5C3/2 are used in Buchla synths. Different vactrols have different response times, but I found this link, which might be helpful. The pdfs include resistance as a function of current, and response times. Response times and resistance also depend on temperature I think.

http://www.datasheetarchive.com/VTL5C3-datasheet.html

If anyone comes up with an emulation patch I would be very interested.