shield to pin one of xlr

I have an einstein phonostage with only XLR inputs. I am constructing a tonearm cable. Most schematics (ayre, boulder, aquavox) recommend connecting the shield to pin one. Some schematics recommended just leaving pin 1 not connected. The shield is either not connected or connected to ground on the phono stage.

What is the advantage connecting the shield to pin 1? I would assume that it is related to how the phonostage handle the pin 1 connection.

I'm not familiar with the Einstein phonostage but generally speaking, connect the shield on the source end and leave it disconnected on the other end. This means that any interference picked up by the shield never reaches the amplifier. You are also less likely to create a ground loop.
You can always test it by running a single wire from the turntable to the phonostage ground afterward to see if it's quieter that way.
I reterminated my Triplanar cable ends with xlr plugs. I followed instructIons that had me connect the shield to pin 1. Worked great with Ayre and Einstein. I think you want the shield grounded somehow, soldering a wire to the end of the shield that can be connected to the ground screw of the phono pre probably gets the job done too.
The proper termination of an XLR connector for a tonearm cable depends on the particular type of cable, and how it's wired at the tonearm/cartridge end. Ignoring rare exceptions like old three-wire tonearms and single-DIN terminations found on B&O turntables, there are two types.

Traditional phono output cable is coaxial, that is, a single center conductor surrounded by a shield. At the tonearm end, the cable is connected in a balanced fashion:
- Cartridge red to Right channel center conductor
- Cartridge green to Right channel shield
- Cartridge white to Left channel center conductor
- Cartridge blue to Left channel shield
- Ground wire to tonearm, headshell, and turntable ground
Note that there are no connections between the shields and the turntable or tonearm ground. For (AES-compliant) dual-XLR termination, the shields go to pin 3, the center conductors go to pin 2. The ground wire may be connected to pin 1 of one of the connectors (*shouldn't* matter which channel) or to the ground post on the phono preamp.

The other common type of phono output cable is shielded twisted-pair, where a pair of conductors are surrounded by a shield. In this case, the tonearm end is wired as follows:
- Cartridge red to Right twisted-pair positive
- Cartridge green to Right twisted-pair negative
- Cartridge white to Left twisted-pair positive
- Cartridge blue to Left twisted-pair negative
- Cable shields both connected to tonearm, headshell, and turntable ground
In this case, the twisted-pair positives go to pin 2 of the XLRs, the twisted-pair negatives go to pin 3, and the shield goes to pin 1 (this is identical to pro microphone termination). No extra ground wire is necessary here, as this function is taken by the cable shield.

As far as which type of cable is better . . . of course, it all depends. Speaking generally, shielded-twisted-pair cables have superior hum rejection, and coaxial cables have lower capacitance. For XLR terminations, shielded-twisted-pair is best for low-impedance, low-output MC cartridges, but high-inductance MMs may work better with the lowest possible capacitance, which usually means a coaxial design. This is especially true with RCA terminations.

Complicating the matter a bit is the fact that phono stages with an XLR input tend to have widely varying designs for the input stage, and some may work poorly when the cable impedance isn't well balanced between the positive and negative conductors, with respect to ground . . . as occurs when a coaxial-type cable is terminated with an XLRs. Ironically, designs that have this issue will exhibit it at the highest input impedances, which are used by MM cartridges . . . which have the most to gain with a low-capacitance (coaxial-type) cable.
Guys, many thanks for the help.

Just did more experimenting. I turned the volume way up to hear the bakground noise. Then ran a wire betw the ground of the phonstage and tonearm, tonearm base or table. There is no significant difference in noise level or sonics.

Also tried the setup by opening the connector at the phono end and inserting a wire betw the shield and pin1. Again no significant difference in noise level.

I am not experiencing any problems with noise at normal volume setting so I am going to float pin 1 and leave the shield disconnected.
Glai, Usually you will want pin 1 tied to the tone arm ground. This would then also be the ground connection of the phono section. While there may be no difference in noise that you can hear, this will eliminate loud pops that can show up due to static discharge.

Furthermore, there is no sonic advantage to floating the shield. The phono cartridge and the balanced cable form a low impedance balanced line and so is relatively immune to cable capacitance and cable artifact, as long as the cartridge is loaded with some nominal low resistance (1000 ohms or less). If this is the case what you will find is that the difference between cables is literally gone, and the need for an expensive cable with it.