ingood wrote a program which will allow to change the default 100% volume of the Dingoo to something you desire. The voume can be between 0% and 100%.

Usage:

Just plonk it anywhere on your device. To use it run: ./volset NUM where NUM is the volume you want between 0 and 100. If you leave this out it defaults to 50.

http://a320.freeforums.org/global-volume-setting-program-dingoo-linux-t737.html