oops, misunderstood.

the next thing i did was to open up the player, remove the drive tray, pull the analogue connector out and test continuity from the gnd pins in the header to the chassis.

I actually removed the main board from the chassis to do this and I was able to see very thin traces which appeared to be for signal which went from the header through some decoupling capacitors to the pre-amp stage. There was also one relatively thick trace that appeared to go to the rear gnd pin, but without de-soldering the header I was unable to see where it went and if it also connected to the front gnd. Obviously I could only see the top and bottom layers but i would imagine that there wouldn't be too much in other layers as to keep RF interference to a minimum in the output stage.

maybe Hugo could post a small section of the PCB design to see what happens on all the layers around the analogue connector?