Logic audio platinum with mac os 9.2 in G4

Hi, I have a G4 dual 1,25 GHZ with Mac Os 9.2. I 've installed Logic audio platinum 4.8 . The problem is that auido mixer does not work...I mean you can hear a track auido in edition window but when you play in mixer.. you can not hear anything becaouse the objetc auido mixer does not worl...I am not sure what is the problem. ¿perhaps I need logic platinum 5 or 6? ¿perhaps it is an incompatibility hardware?...I don't know
please someone can help me ???