The shell of any panel-mounted *metal* flange XLR connector, say on a
facilities panel or wallbox, is usually grounded by its corner or radial
screws to the metalwork, assuming that the panel *is* already grounded - for
Safety reasons. When a flying lead *metal* case XLR connector (male or
female, 3 -pole or more) is inserted there, its shell gets automatically
grounded. Therefore it should not be linked to pin 1 which would get
grounded twice!.
If using lightweight *plastic* XLRs, Caution - there is not always a 4th
pole embedded in the connector.
XLR pin 1 is supposed to be longer than the other two - and so mates first
and breaks last, allegedly.
But the *shell connection tag* of the wandering end metal-cased 3-pole
female XLR cable socket should be linked to pin 1 to make the microphone (or
whatever source) safe and immune from RF.
I always connected studio mic cables' and mic extenders' XLR females from
pin 1 to shell.
Even if the signal-pair part of the cable in a technical area is
interruptible by normalling jacks and patching, the screen should be
continuous to ground.
No matter what series length and how many add-on extenders are used, pin 1
should be traceable to the active electronics chassis elsewhere, which good
practice dictates is always at robust ground potential.
I believe the same philosophy does not always go for *shell connection tag*
of studio/gig wander ends with metal-cased 3-pole MALE XLR plugs used for
taking feeds, foldback, etc.
ANOMALY... If o/p cable metal connector shells are always linked to their
pin1, should the metalwork for an i/p cable accidentally touch the metalwork
for an o/p cable on stage or in a studio, there could be a subtle ground
loop.