I have been using Jamzone on my iPad for the last 4 years, and I'm now in the middle of transitioning to ST3.
In Jamzone I can click a button that gives me a whole long list of available AUv3 extensions, and I use the one called AUDynamicsProcessor to adjust Master Gain to normalize track volume.
However, when I click 'Master Effect' in ST3, it just says "none" and there is no list of available extensions.
I'm assuming the AUv3 effects are already installed somewhere on my iPad, so I guess I'm wondering how to access them in Stage Traxx. Any help is appreciated!