Yes, but I don't know how to make it stick through reboots!
If you go into the VDR menu system (probably best to use the Remote Control function of vdradmin-am), into plugins(?) or setup->plugins? You'll find it! Go into xinelibplugin, then Audio. In there you will see a setting that defines volume control as Hardware or Software. Just change it, and you will hear the volume jump to what it should be. You can even change it back to the original setting at this point and the volume will stay loud.
Problem is, reboot resets this again.... hoping B4 fixes this, but I haven't tuned in my TV channels yet to test...