when I got my CPS2 it had no audio out. if I put my ear to the speaker I could just barely make it out.
From what I was reading this is something that happens sometimes when it thinks the volume it turned up but really it's very low. There were a number of suggestions on fixes involving holding down the menu and volume up button during boot but none of them seemed to work.
how I fixed it was I went into the system menu and then went to the volume section, turned it all the way down then turned it back up again . so it might be worth trying that.