Hexinverter - Red Dragon 

Cheers mate! I do like a big cut off knob (bah dum tish!) a'la SVVCF, Humpback, SARA etc but the Red Dragon is an excellent filter.

Yeah it's a great filter, audio rate stuff sounds killer! Into a little overdrive and then a filter after all that is ace.

Yeah the audio rate stuff is my favourite thing on it. Sounds killer!

Yeah "unstable filter types" or something. To me they all sound different. And interesting this Red Dragon which is "soviet inspired" (polivoks, we all know of course) sounds very different to the Erica Polivoks filters. I think Stacy took this design further, it's more the resonance circuit that get the character in this. I don't have them all to hand to compare but I agree it would be cool.

This is indeed true! The Red Dragon was designed from the ground up, and is not a clone of the State-Variable 2-pole bandpass topology Polivoks filter. Red Dragon is a different class of filter than a Polivoks (or its clones). It's like comparing a 4-pole low pass ladder/cascaded-OTA filter to a 2-pole state variable filter. The homage to Vladimir Kuzmin in the Red Dragon is that to the best of my knowledge, he cleverly discovered the use of these programmable opamps as an interesting way of making a filter without using an OTA or ladders of differential pairs. That being said, it certainly is an "unstable" sounding filter type! Resonance gets pretty wild!

I'd say the MS 20 and this guy are closer than the Wasp, which is just a wacky filter. An ms20 or this will give a nice, wet, squawking resonance, while the Wasp has that crazy ringing distortion.

cheers!

great filters in feedback paths always make me smile.

:)

can you give me a specific timing for that section in the video and I'll listen when I get home.

Sorry, just seen this - yeah starts at 16.34, got a certain Autechre about it..

cheers

I think I went through what was what in the video (can't remember now as I don't keep notes) but I can talk you through it. Basic acid sounds are either a saw wave from an oscillator or a square (original 303 was a non perfect square) into a resonant low pass filter with a basic decay envelope modulating the cut off. That what's happening here, saw wave into the input, then an envelope into the cut off CV input which is fast attack and a decay curve quickly opening then decaying the cut off frequency. There's usually a good amount of resonance of the filter. Hope that helps.