The Magnepan fuse holder and speaker cable terminals have ferrous parts, and replacing the stock fuse with a Supreme 3 won't cure that! Lots of guys on the Planar Speaker Asylum---hard-core Maggie owners---have bypassed the whole Magenpan hook-up arrangement, including the fuse holder, and replaced the stock speaker cable terminals with Cardas binding posts. A set of the Cardas posts may be cheaper than a pair of boutique fuses!