Getting sound out of CD players

I have a relatively simple question: My sound system appears to work fine. I get all sorts of sounds (real and test.) But none of the CD players that comes with Suse 9.1 can produce any sound, such as KsCD and xmcd. These players actually start playing, and the display indicates that the CD is being played: time and tracks advance normally. But there is no sound. I must be missing one simple but vital setting. Can anyone help? Thanks in advance, -sinan