Noise from G4 internal speakers: a follow-up

Uncheck "Play Sound Through Output Device"? Luke Hertenstein writes of a similar problem he had with an older AGP G4 awhile back - even with external speakers connected: "I stumbled upon a check box in the Sound control panel to 'Play Sound Through Output Device.' Unchecking this box would make the hissing go away. I think it was only a problem if the Audio In was chosen as the Input source, but I might be wrong about that. Every once in awhile it would come back on its own, but once I knew how to make it go away, it wasn't a big deal." [Note: This option is only enabled, and thus only relevant, with certain input source selections.] Upgrading to OS 9.1 appeared to eliminate the problem. Selecting "None" for Input source (assuming you have none) might also be a good idea.

The logic board A reader contends: "The problem is the sound chip on the logicboard. The problem started with the G4 Digital Audio 667MHz and continues up to the current QuickSilver. Usually, this is a bit annoying and harmless, but in really bad ones, the sound starts to fade/crackle then die. You won't be able to hear anything from the speaker or headphone jack. Only solution is to replace the logicboard."