Zero Delay Feedback Filter

[KG_is_back]

I've tried switching the filter outputs (lpf0 and lpf1 before downsampling) and it seems to fix the issue. The output seems additionally lowpassed that way (but that might be the work of oversampling lowpass filter)

[tor]

thank you for trying to help. but that is not the right fix. it just makes a notch at nyquist. it is correct only when the two curves entirely correspond.

[KG_is_back]

FIXED... added one sample delay to in1 and out0 ...the feedback probably goes in opposite direction than it should be. (like x0,y0 are actually in feedback)

[tor]

wow, thats close

i added HP and BP, but sadly the fix does not work on all filter types. so the search goes on...

ZDF filter OS DP not yet fixed.fsm

(33.03 KiB) Downloaded 1180 times

and thanks a bunch for trying

[KG_is_back]

Here, this one is fixed for good...
gotta separate the two parts of the filter to maintain right execution order. To transfer double precision values between modules I used round and difference, so the feedback is still DP.

[tor]

sorry KG, this behaves just like my non working version. i hope maybe Trogluddite can provide an explanation what is causing the trouble here. it is quite strange to me as the non OS version in DP works perfectly well.

ZDF filter OS DP not yet fixed2.fsm

(32.38 KiB) Downloaded 1181 times

[KG_is_back]

sorry KG, this behaves just like my non working version. i hope maybe Trogluddite can provide an explanation what is causing the trouble here. it is quite strange to me as the non OS version in DP works perfectly well.

ZDF filter OS DP not yet fixed2.fsm

Now that is very strange... my fixed version works perfectly here... I'm still using Flowstone 3.0.2.0

[tor]

If you look at the yellow graph when you sweep filter frequency towards 20khz you see that it warps and then disappears. You have also left out the regular OS filter type selection so you can not in your example compare the regular (grey curve) and the DP (yellow curve) when selecting different filter types.

[KG_is_back]

here's screenshot

[tor]

i see that, but what happens to the yellow curve when you change filter type to BP or HP?

*Edit: Here with me your second fix shows that the yellow curve is warped and the disappear near 20khz and the grey curve just stays at LP filter type.