Hi, I have a PC rigged up as a music server, its basically empty except for one HDD, the PS and of course a RME HDSP 9632. I want to make up set of RCA and XLR analogue output breakouts for it using good quality connectors and cables and have a few questions :

1) XLR cable
According to the pin assignment tables the XLR cable has pin 9 on the D-type connector as the unique ground. Does this mean that the shielding of both L and R XLR cables should be connected to this pin ? Is there any connection to be made between the cable shielding and the metal hood of the D-type connector ?

2) RCA cable
The pin assignment table for the RCA cable has pins 9, 1, 11 on the D-type connector as grounds. Can the L and R RCA cable shielding be connected to any of these ground pins or is there a recommended grounding configuration. Likewise is there any connection to be made between the ground of the cable shields and the metal hood of the D-type connector.

3) Ground isolation in general
Is there any reason why RME frequently uses transformer isolation for the digital I/O but often uses DC coupling for the analogue balanced/unbalanced I/O ? I would have thought transformer isolation would have been preferable all round, but I may be mistaken. The lack of transformer isolation seems to encourage the use of an external D/A converter in order to get rid of the dirty power supply of the PC. However it is quite possible to power the "noisy" processor, HDD, fans and video card from one power supply and the motherboard/soundcard from a second dedicated hence cleaner supply, but this requires two supplies one in the PC and the second outside ! I haven't tried this yet has anyone else ? Does it make any difference ?

Thanks.