This modification is only intended for the Muffsy Phono Preamp together with the Muffsy Power Supply and Back Panel in the recommended B0905 enclosure. Before you try this, have a look at the other ways of eliminating hum.
Arno just completed building the Muffsy Phono Preamp, and was haunted by distortion. He decided to use the B0905 enclosure for shielding and ended up with a completely quiet phono stage.
Notice also how Arno connected the ground lugs of the RCA connectors in a star pattern. Great idea Arno!
He drilled a hole in the cabinet and connected a piece of cable from the ground screw to this hole.
The reason this works is that the Muffsy Power Supply has a completely floating ground. If you're using a power supply that connects directly to mains power, this solution might inject more noise if not done correctly.
You can see Arno's modification from a different angle in the above picture, and a larger version of his close-up below.