BiquadNonLin
TL;DW: BiquadNonLin is Capacitor2, but for biquad filtering.
A biquad filter is a very basic piece of typical DAW EQs. If you were going to think of the most ordinary, normal, non-special digital EQ that would sound like every other digital EQ, you’re probably going to be stacking up biquad filters. It is the most boring of digital filters, at least ones that are kind of flexible.
Let’s break it!
BiquadNonLin takes the traditional biquad filter, complete with cutoff and Q factor, and applies the same technique used in Capacitor2. That was the one where I read about Murata ceramic capacitors showing striking variations in value, based upon how much voltage pressure was against them. Which is not to say all capacitors do that… but knowing this has happened in the real world suggests that it’s an avenue to pursue. And so, Capacitor2 brought in this interesting nonlinearity based on real-world stuff, like a (in fact literally a) frequency modulation… and then it sat for a while. Because how would you even apply that to a carefully worked out algorithm like a biquad?
The answer is ‘you just do’. Does it produce a clean result? Nope. You can break things pretty thoroughly, especially up near the Nyquist frequency. But you can apply less… I find 0.5 tends to work quite well… and you can get the same kind of nonlinearity.
It’s just that this time, you can do it on a steep, resonant filter, and get that more analog texture on something that’s otherwise very controllable. I’m looking to use this on many things: I think it’ll make for a better-sounding distributed ultrasonic filter, and I’d also like to make a multistage version to use as the guts of a future ConsoleSL… because it should work more like a steeper but less vibey filter, except with the analogification.
Anyway, here’s BiquadNonLin: one biquad filter, lightly broken for your sonic pleasure. Type at 0 is a lowpass, Type at 1 is a bandpass. The biquad tended to explode when I tried to make it do highpasses or notches, but it turned out I could just make the dry/wet an Inv/Wet control, so that means you just use Inv instead, and Type at 0 becomes the highpass (it’s subtracted) and Type at 1 is the notch. If you have a hard time hearing the nonlinearity, setting it to highpass and sweeping it up at high NonLin should make it real obvious.
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All this is free and open source under the MIT license, brought to you by my Patreon.
VCV Rack module
Oh, one more thing…
Today, the first VST3 is out… kind of. I have it up on GitHub at https://github.com/airwindows/Meter and you see it in the video for BiquadDouble. The thing is, I can’t build it anywhere else except a single VST3 on my own machine, for Mac Apple Silicon only. The project on GitHub is all the code, up to date, and it’s supposed to be able to build all sorts of different versions.
You can fork it, you can download it, you can try to get it to compile just like I did. There’s lots of people smarter than me about computers and they didn’t make this meter, so I had to. So, if you can make a Pamplejuce project compile, Meter is yours today, no matter what sort of computer you’re on or what platform you’re targeting. VST3? AU for iPad? AAX? Knock yourself out.
If you get anything to work, tell me how you did it, and everyone can have the result. Otherwise, I will keep plugging away, and eventually I’ll get this stuff sorted out. But if you’re impatient… the GPLed code is there, it compiled for me, let me know how you do :)
Gud
If you make a distributed version (like what UltraSonX was to Ultrasonic) then please release it as a plugin independent of ConsoleSL! Thx
I meant for the non-linear ultrasonic filtering you said you are gonna do with this.
Also I guess you could update channel to have the new analog-style ultrasonic filtering instead of the one it has in channel9 and update all the other plugins (like Pressure5 will now be pressure6 and channel9 will be channel10 or channelX lol) that have ultrasonic filtering built into them.
The only catch is, I think if you are putting it as the first thing in an FX chain (of say a vocal recording that has ultrasonics) wouldn’t you need to have a clean stage there? Then, after that one, it’s fine to have non-linear ultrasonic filtering placed after it.