radio not working

[ren1990]

2005 B7 AUDI A4 avant 2.0tdi

Hi my radio isn't working. I've removed the head unit and have located the permanent live wire (Blue/red). I understand the Audi uses a canbus system and as such theirs no switched live at the head unit. I intend to run a wire from a switched live fuse and connect it to the stereo. Which cable would I connect it to at the stereo end. would I connect it to the blue and red  permanent live wire. Alternatively if anyone has a different option. I would even consider running the permanent live and just rely on switching the radio off after I've used it. Cheers Andy