[hatari-devel] DC and Subsonic IIR Filter for Digi Sound

[David Savinkoff]

Hi,

Here are frequency response graphs of data the filter processed:
(impulse response = 32767,0,0,... 44100 samples for 1 second)

- HPF_Amplitude.png is  Decibels vs log of Frequency [Hz]
- HPF_Phase.png     is  Degrees  vs log of Frequency [Hz]
- HPF_Delay.png     is  Seconds  vs log of Frequency [Hz]

Note that the ticks between the numbers on the Frequency axis
appear to be 2, 5, 9 as in 1, 2, 5, 9, 10, 20, 50, 90, 100 ...
(half way between the numbers is approximately 3).

HPF_Amplitude shows -3 dB at 11 Hz (cutoff frequency).
HPF_Phase shows first order filter phase (single capacitor + resistor).
HPF_Delay shows first order highpass phase advance for low frequencies.

David
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