The shim that 4yanx mentions could be a small sheet of mu metal, at that point nulling the effects of any magnetics. You will also find it titled under "Hy Perm 80", or "Permendur".
I use sheets of it exclusively, affixed to the underside of all of the shelves on my stereo rack.
Unobtrusive, and extremely effective.
I use sheets of it exclusively, affixed to the underside of all of the shelves on my stereo rack.
Unobtrusive, and extremely effective.