Hello to everybody, this is just a curiosity of mine: is there any equalizer which uses zero delay feedback filters? I know this is important in virtual analog filters, especally with high resonance, but I'm wondering if this applies / makes sense also to equalizers (which are a bunch of filters) and if there is any actual real-world example.

Thank You.

Do eq filters use feedback ?

They certainly do. Any digital EQ or filter is basically a big feedback delay as yer two main algorithms are the FIR or IIR filter.

As resonance usually isn't meant to be that obvious in EQs, I'm not sure how relevant zero-delay feedback is, although I guess it might help in modelling transistor-based analogue EQs.

can anybody provide an audio example of the same filter with zero feedback delay enabled and disabled to see what difference in sound quality it makes when all other aspects of the filter are equal (other than the zero feedback delay part)

The different modes in Diva should be enough to provide a clue to that. As I understand it, the primary difference in those modes is how much error the feedback calculation tolerates, so the draft modes behave fairly similarly to a conventional digital filter. You can switch between zero-feedback and conventional filters in DiscoDSP's Corona and the difference is quite dramatic. But other things may be different between those filters.

In Diva, "draft" and "fast" use identical code for the filters at identical oversampling rates etc. The only difference is, "draft" uses a conventional 1-sample-delay while "fast" uses a zero delay feedback solver. The difference is audible with all 4 filter topologies (ladder, cascade, svf, sallen key) once a bit of resonance comes in.

Interisting Q. Where ZDF really shines - is when it's being modulated (and high res - which isn't really used in general eqs), so if the EQ is static - I don't see much use for it. In "analog" moddeled EQs i.e. - with non-linearities - it might make some small difference, but the non-linearities in EQ are generally also quite low & subtle - so I have my doubts. In synths - they rock

Maybe UAD and Softube stuff?

Nope.

0df is braaaand new stuff

all previous filters are garbage

Which is exactly why all music produced digitally before 0df sounds like rubbish

Well, yours does

It's true!

XIls-Lab Le Masque delay has 0df filters, inherited from the Synthix synthesizer.


For other VST effects having odf I think The Drop has some iirc ( But it might be better to verify that with the dev, or in the threads related to this filter VST )

LtZ

Its not an equaliser.

No its a Delay. There are very very few Vst effects with 0df I think. So this can eventually give the OP some clues about the benefit they can bring.

Some other non EQ 0df units has been mentioned in this thread btw if you noticed, without you commenting them...