The best
I’ve tested 5 different good AU compressors side by side on the same file, to see which one works best. Result: Tonebooster for sure. I just wish it had a pre-gain dial, so that you could have full control over the incoming audio level (and the outgoing level through make up gain). Currently you can do it by moving around the threshold, but then need to move around the make up gain to compensate (or turn on “auto” but then you lose that part of the control). Moving around a “pre-gain” dial would keep the “threshold to make up gain” ratio as you have set it up, so it would be the simplest way to choose how much compression you want once you have it all set up as you like.