If you don't already have them download the alsa drivers
(download the driver, library and utilities files).
Read the following install instructions
(you might want to skip the "short explaination of what happens section"
To enable bass and treble (from same instruction page):
To enable bass and treble tone controls, the 'Tone' switch must be turned on.
This can be achieved with the following command:
'amixer sset Tone on'
or "unmute" (m key) the "Tone channel" in alsamixer.
Use alsactl to save and restore this and any other settings automatically.