If you have the volume max'd, you don't have enough gain. If the volume control sits near the bottom, you have too much gain. The idea is to have just enough gain for adequate listening levels and a bit extra for that party and your son to blow the speakers. For less than adequate speakers, volume control and distortion control are fairly synonomous.
Some sources have an internal switch to raise output voltage, which is the same as more gain.
Some sources have an internal switch to raise output voltage, which is the same as more gain.