The ground of the DIN goes to pin 1 of both XLRs.
Should the ground wire from pin 5 in the Din5 connector
be split in two such that each can be soldered to the pin 1 on the
XLR connectors? Or should only the (floating) shield of both
channels be connected to the pin 1 on the XLR connectors?
@nandric , This:
Nandric - for all phono both balanced and unbalanced the arm earth ( 5th pin ) should be a separate wire which you connect to preamp chassis. This simply grounds the arm itself and has nothing to do with the cartridge signal.-is mostly incorrect!
Floating shields on the signal cables should only be connected to earth at one end.
In the RCA's at the preamp end I connect the floating shield ( assuming a twisted pair plus shield construction ) to the chassis by cutting the connection to the RCA and soldering a tail for connection to the preamp chassis. This reduces the opportunity for noise collected by the shield to enter the phono signal in a single ended system.
In this arrangement you end up with 3 earth leads to connect to the preamp chassis - tonearm earth/ground plus left and right channel floating shield earth/ground.
XLR's have a separate -ve signal and earth/ground in a balanced system. Therefore you only need to ensure the shield is connected to the earth/ground pin which is already separated from the -ve signal. The tonearm end is left floating ( not connected ).
The tone arm is in fact the ground (which is the ground wire in a single-ended system). So the arm wand provides a grounded shield to the cartridge wires within. This continues through the DIN connection and splits to the shields of the left and right channels. At the XLR connection it ties to pin 1 which is ground). In this way the shield is constant from the cartridge to the input of the phono section.
Note that the ground is otherwise not part of the cartridge signal and should be ignored by the phono section in any event (otherwise Common Mode Rejection Ratio will suffer).
In a single-ended system it is advantageous to prevent the ground side of the RCA connection from being shorted to the phono preamp chassis (otherwise it is possible to introduce ground loops). So the only ground to be seen at the chassis should be the ground wire of the arm itself and not the minus outputs of the cartridge!