PurestWarmDemo is a universal binary Audio Unit plugin, and another really extreme example of the Airwindows ‘Purest’ series of plugins. To explain why, I need to explain what it does. It’s for individual tracks, and I do NOT recommend using it on a full mix, even though like PurestDrive it is ‘invisible’ and at its best being non-obvious.

PurestWarm is simply the highest resolution asymmetrical saturation in existence. See the video: it’s best used on things like basses, where you might have a type of sound that peaks harder in one polarity than the other. When you put PurestWarm on a track, you pick which polarity you want to distort, and it applies the single most soft-textured distortion in existence, something that in other Airwindows plugins is responsible for adding huge fatness and boosts (try Density for a freebie example!) but in PurestWarm is used in the simplest possible form, only to restrict loud peaks. It’s not unlike PurestDrive (the experiment that started this line of inquiry) but there’s an implementation detail that’s at the heart of what this plugin is about.

When the saturation is applied, it’s done at 80 bit floating point resolution, and when we go back to 32 bit for the buss, there’s a form of dither (really noise shaping) to translate the higher fidelity 80 bit signal back to CoreAudio 32 bit. This is fundamental to how the Purest series plugins get their totally transparent sound, but it’s only relevant when you’re changing the audio, be it ever so slightly.

So, the dither only works on one polarity of the signal. For the ‘clean’ polarity, instead PurestWarm takes literally the input data word, and by that I mean the exact variable holding the input data, and passes it through to the output. Doesn’t even assign it to another variable, much less ‘multiply it by 1.0’ and call that the same thing (in floating point, that’s not always true if your 1.0 and your audio data are at different floating point scaling factors). PurestWarm literally goes into bypass and is not there at all, for one polarity of the output. For the other, it’s doing that ultra-high-quality saturation and noise shaping, at 80 bit.

I’m really happy with how this one sounds, even though I think it shouldn’t be used on full mixes. Too much warming! Keep it to pads and basses, though I’m not the boss of you. If you DID want to whack one whole polarity of your mix in the name of warmth, there is no more transparent way to do it, anywhere in digital or analog. And if your mix is coming out with all its transient spikes on one polarity, it might even make a kind of sense (though I still think it best to address that at the individual track level).

It’s a permanent fixture on my electric basses now: because it can be. Nothing about it hurts the sound, it just throws a whole bunch of warmth and makes the instrument more manageable and easier to mix. A true secret weapon, that will never sound like you put on an ‘effect’.

PurestWarm is $50.