I wonder if you are using just the line out. I use a cable that has two large jack plugs one end which are connected to the "MAIN Left and Right" on the Keyboard (not the Aux) and the other end has a small white jack and a small red jack which is connected to my amplifier's Left and Right sockets. This works just fine for me.
Other connections are to my Mini Disk Player/
Recorder, a stand alone CD Player Recorder and an old Cassette Player/Recorder.
All this enables me to produce or copy any CDs of my own, transfer tapes and Records to CD.
I received a tip from a friend when we were setting up this gear and that was "remember Red to Right and its hardly likely you'll ever go wrong". So far, it has proved itself.
Hope this helps.
Aud (U.K.)
[This message has been edited by Audrey Turner (edited 08-18-2006).]