Oh, well if the other Alpine is running fine off that cabling then it isn't looking good for your amp unfortunatly
That voltage looks spot on, with the car off you should be getting around 12V and when it's running you should have around 14.4V
You might as well try and replacing the fuse, however; i wouldn't have thought you'd even get the protection light if the fuse had blown, but never having blown a fuse in an amp I can't confirm this.