Filter with feedback?

[mesoneir]

Hi all, long time lurker, hoping to get some guidance from people who know more about this than I do.

I've been trying to replicate the feedback behavior of u-he Diva's feedback knob in hardware. For context, I've been watching the output on an oscilloscope and the waveform coming out of Diva's feedback path is measurably different from anything I can get out of software filters. The nonlinear saturation is clearly tied to the filter's resonant behavior in a way that software filters don't come close to.

My source material is mostly digital, chiptune style leads and Zebra 3 patches, and the goal is to add genuine analog weight and harmonic saturation without just slapping a saturator on the output.
I've been looking at the Befaco Pony VCF in a small Eurorack case as a potential solution given its normalized feedback path. Has anyone achieved something close to the Diva feedback character in hardware? Would love to hear what's actually worked for people rather than guessing.
Thanks in advance, any direction appreciated.

[Benedict]

The thing with feedback on a Model D is that it is instantaneous - at the speed of electrons. BUT in software, everything moves at the speed of packets. So when you send a sound out of somewhere, to somewhere else for meddling, then back from whence it came, you have delays. More so, once the software realizes there is a feedback loop that could destroy the universe.

These are smallish delays, but once you have a few of them, they spread so you get a ringing like a comb filter in your feedback - as that is what you have - a Flanger. Modulating the signal helps smooth that but it happens.

IF your aim here is organic then there are other easier methods like:

I follow this with Master Bus Compressor and a light Saturation

The other thing to be aware of is the tendency for digital to be exact with low bass and high treble so a mix feels less intimate from lack of focus on the mids (where we hear best). There is no single on-button thing here as it is a total mindset as to how a record was made in the 70-80s compared to now.