When I reboot, the volume on the PulseAudio sinks is set to 100%. I know how to change the volume using pactl set-sink-volume, but that is only set temporarily. I could write a script that is run at startup, but it will not be applied if I connect a sink later. (i.e. a Bluetooth speaker)

Is there a config file where I can set the default volume that is given to a device when it is first loaded by PulseAudio? Or even the master volume at startup?

Clarification: The application is for a headless linux box, so the system shouldn't have to be rebooted and should be able to accept new devices without having to connect via ssh to adjust volumes, etc.