[sdiy] AS3320 VCF chip - some queries

Pete Hartman pete.hartman at gmail.com
Sun Nov 11 18:19:58 CET 2018

On Sun, Nov 11, 2018 at 10:32 AM Tom Wiltshire <tom at electricdruid.net>

> 2) The resonance response is tilted to the high end.
> It seems to require a lot more resonance CV (ok, current) to make the chip
> oscillate at the bass end than at the treble end. Similarly, the amplitude
> of oscillation increases as the frequency rises. Why is this? Is there
> anything I can do about it? Should I even care?

If I compare this with the behavior I've seen in other lowpass filters that
self oscillate, even without CV over the resonance, it seems consistent.
Typically I need the frequency at 50% or higher to get it to start
oscillating -- I can then commonly turn it down and get lower frequencies,
but my experience is that if the filter is going to oscillate, it's always
easier to start the oscillation at a higher frequency.  And typically if I
turn it "too low" then it stops oscillating again.
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