[sdiy] What would be THE best, most versatile VCF available on DIY community ?

[Neil Johnson]

Lanterman, Aaron wrote:
> The Synthex filter is unique.
>
> The way it forms a two-pole filter with variable "Q" is to cascade two usual first-order LP filters (for instance) and then feed the output back to the input. I can't seem to find my notes on it now, but I remember working out the transfer function. Changing the feedback, IIRC, doesn't give you a Q (as typically defined for a 2nd-order filter) that varies independently of the "fc" (usually called the "cutoff"), as in the case of a State Variable Filter or a Sallen-Key. The fc also changes. So there's a subtle difference in how it responds.

Sounds more like a biquad arrangement - in your analysis did you
notice if the bandwidth remained constant as Fc was changed?

Cheers,
Neil
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