No sound, not through speaker, mic or headphone

My iPhone 3GS does not have any sound at all. The earpiece, speaker, and microphone do not work, also sound through the headphones does not work. I thought it was stuck in headphone mode, but that's not the case. When i press volume with the headphones in, it says "headphone volume" and when I plugh them out then it says normal volume again.

In short, there is no sound in any possible way. No waterdamage, and the dockconnector has already been replaced.

Is there like a sound chip on the logic board that might be broken, and can I fix this? Or do you guys think it's something else?

Any help would be greatly appreciated!

Thanks,