Add the PPA to your sources by creating a new file for the Amarok PPA:

gksu gedit /etc/apt/sources.list.d/amarok.list

Then in that new file add the following two lines:

deb http://ppa.launchpad.net/bogdanb/ppa/ubuntu jaunty main
deb-src http://ppa.launchpad.net/bogdanb/ppa/ubuntu jaunty main

Add the key for the PPA:

sudo apt-key adv --recv-keys --keyserver keyserver.ubuntu.com \
0x1d7e9dd033e89ba781e32a24b9f1c432ae74ae63

Now update your sources, remove Amarok2 and install Amarok1.4:

sudo apt-get update
sudo apt-get remove amarok
sudo apt-get install amarok14

And enjoy the best media player ever made!