
That's how we roll in modular lands, a million ways to skin that cat

OK, the first half of that confirms what I suspected. But the second half leaves me doubting what, specifically, a "resonant" filter is. Is it simply *any* filter that has resonance? If so, is there such a thing (in traditional subtractive synthesis) as a non-resonant filter?Stab Frenzy wrote:All self-oscillating filters are resonant, not all resonant filters self-oscillate.
Yes and yes.CfNorENa wrote:OK, the first half of that confirms what I suspected. But the second half leaves me doubting what, specifically, a "resonant" filter is. Is it simply *any* filter that has resonance? If so, is there such a thing (in traditional subtractive synthesis) as a non-resonant filter?Stab Frenzy wrote:All self-oscillating filters are resonant, not all resonant filters self-oscillate.
(apologies, again, for this continued hijacking -- I did look around on the web for info, but can only find complicated engineering theses with, you know, like numbers and graphs and stuff)
Regarding "Self-Oscillation"CfNorENa wrote: If so, is there such a thing (in traditional subtractive synthesis) as a non-resonant filter?
Interesting. Never knew that this was what resonance was doing to the signal.piRoN wrote:To go into the technical side a little, resonance is really just adding a feedback loop somewhere in the filter circuit, that feeds the output back into the input in some way.
Two more questions: what, specifically, is that "peak?" My understanding is that the resonance somehow "emphasizes" the frequency (as determined by the cutoff of the filter), but I'm not sure what that actually means. It's not simply a boost in volume per se, is it?piRoN wrote:The reason you end up with a peak at the cutoff frequency is to do with both the phase response of filter networks, and the specifics of how you implement the feedback loop (you can play with stuff like inverting the feedback signal and so on).
Yes, it is a boost in volume at that frequency. If it's a low pass filter, the response is essentially flat below the cutoff frequency, boosted at the cutoff frequency and attenuated above the cutoff frequency. See below.CfNorENa wrote:Two more questions: what, specifically, is that "peak?" My understanding is that the resonance somehow "emphasizes" the frequency (as determined by the cutoff of the filter), but I'm not sure what that actually means. It's not simply a boost in volume per se, is it?
It's just a flaw of that particular design. There are filters which copy the Moog LPF but add corrective circuitry (often switchable) to not attenuate the signal.CfNorENa wrote:And why does increased resonance attenuate the signal in some filters (famously the Moog ladder, but other 24dB filters as well, like on my SH-2), but not in others (e.g. the SEM)?
Yes, it's a boost in volume - the same as using a parametric equalizer to boost a frequency range.Two more questions: what, specifically, is that "peak?" My understanding is that the resonance somehow "emphasizes" the frequency (as determined by the cutoff of the filter), but I'm not sure what that actually means. It's not simply a boost in volume per se, is it?
I'm not really too clear on the ladder filter, but I'd suspect that's to do with the specifics of how the feedback is implemented. If the resonance in a filter is feeding back an inverted version of the output for example, you'd expect to see phase cancellation below the cutoff point (where the filter's phase response is closer to zero degrees), and then increasingly less cancellation as you approach the cutoff frequency where the phase starts to get shifted significantly by the filter. So the more feedback you add, the more you attentuate the sub-cutoff frequencies.And why does increased resonance attenuate the signal in some filters (famously the Moog ladder, but other 24dB filters as well, like on my SH-2), but not in others (e.g. the SEM)?
Scotty would be so lucky. It's more TNG technology. When I program it, I feel more like Data tweaking at android speed.Bitexion wrote:Damn, the Matrix-12 is more like a spaceship than I imagined. It looks like Scotty configuring the Enterprise for warp speed in the 1960s.