Apart from the audio issues related to OS X 10.3.2 mentioned above, we've previously covered a number of reported audio issues with the Power Mac G5. A number of MacFixIt readers have reported noise problems (hiss, static, etc.) when using the optical audio output. After experiencing a similar problem with his Klipsch ProMedia D-5.1 system, reader David Sinclair emailed Klipsch and recieved the following reply:
"The optical outputs on the G5 for some reason will send out a dirty signal, one of our sales reps is working with Apple to try to correct this."