Pointless. A tube amp must have a load. If the fuse blows you have protected your vintage cabinet at the expense of the amplifier.
Your ears, used wisely, are your cabinet(s) best defence.
Edit: A speaker fuse makes more sense if you are using vintage SS amps. Those very often failed and shorted the output to one of the supply rails.
Last edited by BassmanPaul : 07-08-2013 at 03:36 PM.