I got my first Mcintosh yesterday. Hooked it up and sounded great with Trio preamp into a Eminence Commonwealth. Shut it down to change over to the 4ohm tap for a 212 K120 cab and upon power up loud hum and blown fuse. New fuse, tried again, same hum and blown fuse. Thought it might be the 4ohm tap so I hooked it back up to the 8ohm 112 cab same. Took it into the Kansas City Mac tech and he said it sounds like a transformer and I am screwed. It will take a week or so before the tech does a diagonstic on it so I am remaining optimistic. But I think I killed my Mcintosh.