I have read a few posts and googled this issue, but have not found any that are exactly like this, so thought I would see if anyone has experienced this: I have a 17" G5 iMac, 1.8ghz, "gen 1" as it were. When using the internal speakers, there is a significant amount of hiss, and as I turn up the volume (of which there is very little), at just past 1/2 volume... the sound (and hiss) goes away. No sound at all. If I plug in external speakers/headphones the sound is excellent, very clean etc etc. If I plug in externals once I've exceeded the level point where the internals shut off and then unplug the externals, sound comes out of the internals (albeit low and with mucho hiss)... Any ideas? TIA!