- Antoine Rousseau antoine@metalu.net [2024-04-11 13:40]:
That doesn't seem incorrect to me; after all, a lowpass filter at 0Hz implies that its output is constant (any change would involve frequencies > 0Hz).
Thanks Antoine,
Why does a lowpass filter, that has a cutoff frequency of 0Hz imply that it's output is constant?
I will describe the problem again hoping that I will understand it better myseld: I have an oscillating input signal that has some DC offset (unipolar sawtooth from phasor~). I fade this signal's amplitude to -inf dB using [line~].
I also fade down the filter cutoff (defined as the -3dB point of the filter curve) from 400Hz to 0Hz. The filter will then continue to produce an non-decaying output.
If I fade down the filter cutoff down to only 1Hz, it's output will decay (somehow counterintuitively to me). This is the part I don't get.
I understand that vcf~ is a resonant filter, and it can have a gain greater 1 around the cutoff frequency, especially for high Q values. The above behavior can also be observed for Q=1.
Thanks for all hints! Peter