I reinstalled 10.5.8 SEVEN times in order to trouble shoot the G4 Titanium sound problem. I tried every tip listed on the internet with toothpicks, headphone jack, PRAM and PMU. I discovered that 10.5.7 works JUST FINE so rolled back until I can find a solution. The 10.5.8 combo does something with Core Audio that is beyond me but hope someone can help.
THIS IS A SOFTWARE PROBLEM THAT APPLE HAS IGNORED. You don't need to replace your motherboard. Just rollback to 10.5.7 and the problem is no more. But you miss all the software that runs on 10.5.8.
I don't know how or where to report this to Apple. I hope someone helps out with this as it is a big problem for many.