FabFilter

Greetings,

I'm trying to figure out why the signal is still being altered when everything is at zero and even the band is off. I would expect a clean digital identical to the source signal when everything is off. Of course, I can bypass the plug-in for this but it's intriguing what's going on under the hood by default because this would mean that "behind the scenes" processing would add to the actual processing we're doing on purpose.

probably the soft clipper on the output.

There is indeed a soft clipper and a small third order harmonic in the output stage.