Hallo, David F. Place hat gesagt: // David F. Place wrote:
I'm trying to understand J07.oversampling.pd. Is the structure of the 3-pole, 3-zero Butterworth low-pass filter specific to the 16x upsampling? Should it be different for 32x upsampling?
I'm pretty sure it should be different. Generally the numbers you put into the cpole/czero objects of Pd are the coordinates of points in the complex plane, where the frequencies are mapped to angles of a circle. The angle PI or 180 degrees corresponds to the Nyquist frequency.
So depending on your samplerate you will have the same angle in the plane or the same pole/zero point correspond to different frequencies. For example PI will be 22050 for samplerate of 44100, and 24000 for a SR of 48000 Hz and then everything else is scaled accordingly.
Frank