Re: [LAD] Stabilising self-oscillating filters?

On Mon, 2007-08-27 at 11:35 +0200, Fons Adriaensen wrote:
> On Mon, Aug 27, 2007 at 12:32:26AM +0100, Gordon JC Pearce wrote:
>
> > Something I've been wondering about recently is this - if you implement
> > a digital filter, how do you maintain stability when it's pushed into
> > self-oscillation? Most "real" synths seem to put out a slightly clipped
> > sinewave when in self-oscillation. Might it be as simple as an atan()
> > clipper in the feedback loop?
>
> Yes.
>
> You can use atanf(), tanh(), x / sqrtf (1 + x * x), ...
>

So that would hold it around unity gain, maintaining the oscillation
without going hugely offscale?

I did briefly consider a simple "compressor" in the feedback loop with a
shortish (a few cycle's worth) time constant, the idea being for it to
work like the lightbulb or thermistor in a Wien Bridge oscillator.

Gordon

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Received on Mon Aug 27 16:15:02 2007