Yo, D! I have found that the Sony CD-It brand works well and doesn't cost much if bought in bulk (aka "brick"). Make sure you get the high bias tapes to get the optimum sound for your recordings. As for the demagnetizer, if you mean one made for regular recorders, it should work fine. I would recommend that you follow the instructions in your manual carefully to prevent damage to your 414. I hope this has been of help
chipper