DSP Robotics Support

http://www.timstinchcombe.co.uk/index.php?pge=diode
http://legacy.spa.aalto.fi/dafx08/papers/dafx08_06.pdf

Info here.
Seems I misremembered - more like transitions from 18dB to 24?

k brown

A diode ladder filter model needs to incorporate nonlinearities in order to stabilize self-oscillation. How exatly this is done seems to be a tricky thing, and the folks at KVR can get quite passionate about it. I admire the enthusiasm of these guys and the effort they put into emulating the old analog devices ever so faithfully, including even imperfections. I can follow that road only to some degree, as I find it equally if not more fascinating to explore entirely new possibilities which were out of reach in the analog era.
That being said, there is a Moog ladder filter emulation somewhere on this forum.

Guess I'll just stick to a couple of 2-pole biquads in series for my VCS3 Putny emu. Other folks can go nuts on the filter if they want.

Thanks for the input.

k brown

k brown wrote:Guess I'll just stick to a couple of 2-pole biquads in series for my VCS3 Putny emu. Other folks can go nuts on the filter if they want.

Thanks for the input.

k brown

I'm probably going to be shot down here but what about cross-fading, based on the cut-off control, between a 3 pole and a 4 pole filter?

I shall await a smack round the head

Cheers

Spogg

That's what I did in the Synthy P - only I cross-faded between a 12dB and 24dB.

Well… I’ve had a very interesting time reading all about wave folding. I’d never come across this before Mr Brown raised the question.

This is a very powerful technique which differs to subtractive, FM and additive synthesis for tone generation. I’ve watched and listened to loads of videos, pored over circuits using op-amps and transistors and finally worked out what was going on. Pretty much anyway. There are many variations on this theme and several manufacturers, not just Buchla, have their own take on this technique.

I’m so impressed with my initial experimental results that I intend to make the “Quilcom Folder” to explore it further. I don’t normally post a synth until it’s finished but I know Mr Brown, and maybe others, were interested in how it could be done in Flowstone. So I’m uploading an early development stage, dev 6, for your interest and maybe Mr Brown could make use of the folder modules in his Buchla synths.

The folding engine provides up to 16 folds with a timbre knob controlling the amount of folding, a Symmetry knob and a selection of 3 types of folding. To my ears, and from what I saw of waveforms on the internet, the Rectified half wave option seems closest to the Buchla system and there is aliasing present like in their 259e complex oscillator which uses mixed digital and analogue techniques.

Since this is an early proof-of-concept prototype there is no LFO modulation, presets or anything much but even as it is you can get some very interesting sounds out of it. Plus, I intend to experiment further with symmetry control and much more.

I have to thank Martin Vicanek for ASM optimising my DSP modules used here, which were originally for the Quilcom NINE for an entirely different usage. I’m very happy with the low CPU use considering there are 16 of these running for every note played.

Hope you get some interest from this technique.

Cheers

Spog

Oops - looks like I may have started something!

I'd love to incorporate this in my 'Buchlas', but i don't think I can - I only have SM; guess I'll have to leave that to you FS'ers.

k brown

Just gave it a listen in my trial version of FS - it sure does sound Buchla-y. As I suspected these waveforms are just not really doable by mangling the stock Oscs in any way; I got sort of close with different arrangements of 3-op FM, but not close enough - had a hunch it was going to require writing code.

Go Spogg!

k brown

k brown wrote:Just gave it a listen in my trial version of FS - it sure does sound Buchla-y. As I suspected these waveforms are just not really doable by mangling the stock Oscs in any way; I got sort of close with different arrangements of 3-op FM, but not close enough - had a hunch it was going to require writing code.

You've kinda made me think I'd like to try doing this with Prims now

Anyways, here's dev7. The main change is I've added a 4th folding mode which I think is even closer to the Buchla one. It involves clamping the incoming signal's negative peak to zero (re-using the clamp that Martin made for me) so folding only happens on the positive peaks. Sounds great on Triangle inputs.

Next is to try out a Tanh(x) saturation to emulate the diodes in some of the circuits I saw...

Cheers

Spogg

Well first of all thanks to k brown for sharing these. I can't imagine how much work it must have taken to create this collection. And also thanks to Spogg for tidying the folder up. My main interests are in the dll.

NOTE
There was a small problem with the initial download - (it contained a folder that was difficult to delete)
and I have edited this post to let you know that the problem has quickly fixed.

Should you ever find it difficult to delete a folder with a name ending with a .
scroll halfway down this link for a very simple solution; http://stackoverflow.com/questions/4075 ... with-a-dot