Rhythmbox is default Audio player in Ubuntu 12.04 Precise. Rhythmbox doesn't have Equalizer. So now you can install plugins for Rhythmbox, these package include following plugins: Equalizer, Jump-to-Playing, Tray Icon, Microblogger, Tablature plugin, JumpToWindow and more.
To install Equalizer and other plugins for Rhythmbox in Ubuntu/Linux Mint open Terminal (Press Ctrl+Alt+T) and copy the following commands in the Terminal:
After installation go to "Edit" -> "Plugins" -> Enable "Equalizer"
That's it
To install Equalizer and other plugins for Rhythmbox in Ubuntu/Linux Mint open Terminal (Press Ctrl+Alt+T) and copy the following commands in the Terminal:
That's it
Source: Ask Ubuntu