It is possible. I use the old scart output (the cable came with the console) with white, red and yellow plugs to setup my audio. The plugs goes as follows: yellow is for video (old analog video format) and white and red are for audio. So all you have to do is plug the audio lines into your sound system as if a normal rc cable and then change from PS3 settings the audio output device.
This approach however requires something that covers audio input via RCA. In my case I have 2.1 speaker setup (2 speakers + sub) which has input for audio. With say, a headset this would not work as PS3 doesn't have support for 3.5mm audio jack.