ground lifters - worth the purchase price or no?

[JLNorthGA]

We have a nasty hum on the powered monitor speaker near the electrical panel (downstairs in the dressing room area). Way too far to run a power cord. The signal cable runs right by the electrical panel. The signal cable running to the monitor speaker is a TRS cable.

I did check it with a 3 prong to 2 prong adapter - removed all the hum. I did remove the adapter after testing.

I haven't tried it with a regular speaker cable - that comes next.

Research on this site and other have suggested the following items as possible solutions as well as making sure that everything has the same ground.
We do have three-phase power coming into the building - I have no idea if the different receptacles are on the same phase (or if that would make a difference).

VTG Ground Lift Barrel | Musician's Friend
Rolls DB25b Direct Box/Pad/Ground Lift | Musician's Friend
Ebtech Hum X Hum Exterminator | Musician's Friend
LIFTER - Catalog - Whirlwind
ISOXL LINE LEVEL ISOLATION TRANSFORMER - Catalog - Whirlwind
ISO 1 - Catalog - Whirlwind

 

[museav]

An input transformer would be the technically preferred fix. Lifting the audio signal (not power) ground at a device input is an easy and often quite acceptable fix.

I have reservations about the HumX. In theory, it breaks the power/safety ground until that ground would be needed but some of the experts in that area point to its apparently not carrying a UL, CE or any other testing agency label and that it is only rated at 6A, something many overlook. Those are likely relevant in that while the theory behind the HumX may be sound, the components that can fit within the device are likely limited in what they can handle and thus some of the very situations that would trigger it to provide a ground path could also potentially cause it to fail in an unsafe manner. So better than simply breaking the safety ground but perhaps not by that much.