Bandpass filter that does not self-resonate

Hey, is there a bandpass filter that can be ridiculously sharp? I’m interested for modal synthesis purposes…

Another way of phrasing my question is that I want a bandpass filter that does not go into self-resonance at very high Q values. Simple digital filters (e.g. biquad) behave this way, but the filters I’ve encountered in VCV, unsurprisingly, try to emulate analog filters. Is there a straight-up biquad? I suppose this is something I might be able to create myself…

I’ve now browsed through all the free plugins available through the plugin manager (!) and I found no such filter. Should be easy to port somebody’s biquad…

Why you assume that an Biquad Filter can’t self-oscillate?

you are looking for Parametra

Parametra is brutal

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Vult Stabile (state variable filter) and Ferox (CMOS) have band pass modes that do not self oscillate. The Q is not super sharp but is useful for modal synthesis. Check my flute sounds on this video

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An off-the-shelf biquad filter is a linear transfer function; a linear function’s output is proportional to its input, so if there is no input, there is no output. Unless I’m quite mistaken, you have to add noise and non-linearities into a digital filter to get it to self-oscillate.

It looks like Parametra runs in series - a similar effect to the one I’m after would be to use a broad bpf together with tight peak filters…

I also found Mr.Q KlirrFactory, which seems to be able to do what I’m after (it’s evidently designed to be a full instrument in itself…)

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feed the input with 1 sample pulse is enought to make it ring, and non-linearities is not necessary, you need only to take care of it’s pole and zero stage to make the filter stable.

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cool - I know a little bit about DSP, but, you know what they say, a little bit of knowledge is a dangerous thing…

Wouldn’t one of the various “resonators” or “resonant comb filters” be what you want? Those things give enormous control right at the edge of oscillation, and have precise pitch tracking of the CV. Or at least good ones do.

A comb filter can be used to similar effect (I’ve been having fun with Hair Pick), but a comb filter has many/infinite peaks at regular (exponential) intervals whereas a bank of bpf’s would have N peaks which might have arbitrary freq, Q, and gain. Further alternatives include a sine bank/additive synth controlled by an envelope follower, vocoder, convolution, etc.

So, like, I’ve been playing around with existing tools (Elements and Rings, Hair Pick, etc.) and getting effects that I enjoy a lot. Not having found precisely the thing I imagined, I am exploring within constraints. This is a happy place to be :smiley:

One solution to get precisely the effect I had in mind is to use a sine bank (e.g. BogAudio additator), record a short impulse, and then put that into Nysthi Convolvzilla (duration of impulse controls the Q, effectively). This is rather the opposite of “CV controllable” as far as workflow, but it does what I had in my head.