Is there a way to transmit all sound over wifi from my tablet to my pc?
In general it is at the moment impossible to stream all audio from your android to another receiver.

There's no app which can help you because android itself has no APIs for grabbing audio.

But sure you may use a specific player, e.g. one for YouTube and one for music and so on.

I really know what I'm talking about because I'm developing an app for general streaming audio since several months (it's really hard work with rooting, kernel-module etc.).