SuperVolu 2 removes the change in volume caused by other plugins. This helps to determine the impact they have on the sound character, isolated from their effect on the volume.
For example: You may want to insert a tube saturation plugin in a channel, but the plugin changes both the sound character of the audio and its volume. This makes it hard to understand exactly what the tube effect does to the sound. You can use SuperVolu 2 to make sure the tube effect does not change the volume of the sound significantly, and then you can understand better what it does to the sound character.