I have read in this litany recently several confusing or contradictory
remarks about Earth/Ground loops and even alarming advice to disconnect a
link designed to ensure safety!
It led to my chipping in with the following.....

Simple Earthing rules for a) safety and b) good practice

Exploratory:
Before wiring up a studio/Control Suite, trace for reliable Earth or Ground
point as being permanently
intact and done in a proper or fatter gauge, all the way from your incoming
supply board.
If poss, have two or three supply rings, separate ground ring bus/ses of
supply outlets for programme equipment
from ground ring bus of those needed just for utility purposes.
Observe industrial/domestic wiring regulations issued by relevant
Electricity Authority.

Recommended:
Use RCD breakers on each ring - to trip should a leakage fault
situation arise.
These trip fast, actually in 2 cycles of AC. You can simulate such a fault
with the Test button which
should be pressed at least once a fortnight if poss.
Always ground each bay or rack (bond it to supply outlet ground so it's
always safe, never ever compromise its ground status) and every piece of
rack-mounted or free-standing equipment that has a metal case or fascia or
connector shields (unless it is "domestic" and has a 2-pole mains lead/cord,
say, fig-8), to a clean ground.

Ensure main mixer's tech ground and monitor amps are grounded close to one
another. This is the production area nucleus.

Never bother to attach the screen of a "balanced" output circuit at the
detachable plug-in connector, unless cable is going via Source jackfield.
See next....

Always attach the screen at the detachable plug-in connector to the
"balanced" input (mic or line) cct and at the Destination jackfield.

On jackfields never link sleeve of upper jack to sleeve of lower jack if
normalling exists between them!
Buy both screened and unscreened (or better, screen terminated at one end
only) patchcord types.

On mic XLR leads, but only at the mic skt end, if available, connect shell
tag to screen at pin1.
This avoids stray capacitance, etc.

Ask your techie to:
Check out, on amplifiers that are hum-prone, that the input screen is
traceable to a point nearest 0V (common rail of dual polarity PSU or of
single rail PSU)
of storage electrolytic, which if single rail is often made to chassis.

Try to add Earth/Ground lift toggles connecting/isolating pin1 at o/p XLRs
of portable mains-operated gear, and at DA o/ps where necessary or when
feasible.

Jim