TL;DW: Interstage is a subtle and sophisticated analogifier.
Interstage is one half of an experiment. I pitted my ability to use my weird techniques (interleaved IIR, slew limiting, etc) against my new biquad filtering techniques, in the battle of the bandpasses. The biquads could give me total DC rejection and total rejection near Nyquist. My more distinctly Airwindows tricks could give me new sorts of nonlinearity and tone. Which would win?
This isn’t called ‘Biquadstage’, so that might be a bit of a giveaway.
Interstage isn’t a loudenator. It doesn’t really clip (though it does go dark as you push the highs harder, in a way I’ve never done before). It doesn’t even preserve the output peaks of heavily limited material: it’ll reshape lows in such a way that the peaks might go up slightly as the deepest lows get rearranged, and it doesn’t really eliminate DC offset either. So what does it actually do?
Two level total of three pole IIR highpass which subtracts a pre-averaged sample and slew limits (all right, clips) against not the direct signal but the initial stage IIR lowpassed reference point used as part of the highpass. Oh, also the average it uses isn’t the previous input sample, but the slew limited highpassed output.
No, I am NOT making that up. That’s literally what it does, you can see the code.
What does it sound like? It sounds like running through an optimal analog stage. The lows are reshaped in a characteristic way for a capacitor-coupled circuit that still allows extended lows: this doesn’t suppress much if any extreme bass. It just massages it a bit. The highs run into active component electronic limits, but unlike other approaches (Channel for a bit of grit, Acceleration for ultra-clear) this is restricting treble slews based on the general amount of energy in the circuit. So it goes darker in a peculiarly analog-like way I’ve not done before, sounding still clear and trebly for most audio, but confining the craziest most digital-sounding treble swings into a zone that sounds like hardware. And this is without thousands of math operations of heavy processing: unlike overprocessed analog modeling, this one nails the ‘energy coming out of analog circuitry’ without blurring or thinning the audio at all. If you don’t need what it’s doing you’ll hear no change at all. Only when ‘excessively digital bass and treble’ show up to interfere, does Interstage kick in.
I’m pretty sure Patreon is still up, so what you should do is what you should usually do: don’t take my word for it or rely on my peculiar demos. This time, you can’t even if you wanted to! But you can download the plugin and try it. Throw it on something, preferably something you’d like to make a little more analog-ized, and see if you can pick out the differences. Interstage does not distort or saturate, so it shouldn’t change your gain staging or the density of your tracks. It simply focuses stuff a little for you, in the way that real analog circuitry inevitably does, and it’s a new flavor on that theme. It’s designed to work optimally at any sample rate you give it, and guaranteed not to diminish any of your tones (unless those tones require strangely artificial sonics that can’t exist in nature: if so, put this on your OTHER tones and you’ll have a nice contrast).
I hope you enjoy Interstage!