I am installing a Philips CEM3000B DAB head unit in my 1999 A3 TDi (non Bose, just rear sub with speakers) using the PC9-404 wiring adaptor (the Philips HU has RCA line outs) My original Audi radio had a brown cable connected to the back of the metal casing (an earth I assume). The thing is with the Philips this cable is not so easy to attach. The rear of the unit has a black paint or plastic coating an I am not sure if this part can be earthed. The rest of the unit is metal but to attach here will cause difficulty getting the unit to fit in the dash. My question is do I really have attach this cable to the new casing? Is it just for reducing interference, in which case I will leave it off unless I get interference problems? Any help would be greatly appreciated. p.s. if you saw my earlier post about using a Blaupunkt Woodstock with FM splitter I have moved on a bit since then! Great help from Rob put me straight on NOT using the splitter. Also the Blaupunkt I was after on ebay went for over £140 so I decided to go for something new for that kind of money. I decided to go for the Philips which has just come into Halfords. The advantage over the Blaupunkt is that it takes larger media - I have tried an 4GB USB with success. It also comes with a magnetic DAB aerial.