By default, Systemwide turns your output device to 100% and configures the Systemwide virtual device volume to match the previous volume of the output device. This is done to avoid two gain stages in the signal path to your output device.
It is possible to turn this feature off by unchecking 'Adjust output device gain' in Systemwide Settings' Audio view.
1 comment
Out of interest, why would I want to avoid two gain stages?