Hard Vacuum refers to vacuum tubes, and as you’d expect it’s a saturation device but with some interesting twists. It’s got a warmth control that brings in second harmonic and nonlinearity like you might see in a class A tube design, but set up to be abused if you’d like to produce exaggerated effects (that aren’t really ‘warm’ anymore, but if you want to play nice, don’t push this control too far). It’s got a nice Airwindows sine-based saturation curve… and it’s got a control called Aura that will bring out sparkly highs and hot searing overtones you might not have heard from a plugin before.