Comment 1 for bug 488513

You can control headphones. Plug in your head phones and start an application that uses them, say Rhythmbox with some music. When the music is playing look for the speaker icon in the top(default) panel of the Desktop, right click and choose Sound Preferences. When the Sound Preferences window opens choose Applications. You should see a volume control and be able to adjust the volume. You can also select a 'Connector' which can be amplified (or not for earphones).

pulse-audio had a 'tricky' birth but can allow full control over any input/output device. It does have more than one volume control however, in the above case it has 'Output volume' in Sound preferences and also control through 'Applications' tab (which only becomes visible when an application is actually running). A shortcut to the 'Output volume' is utilised by left clicking the speaker icon. Taking the two controls together you can set various 'default' settings for different applications.