Most likely it is internally fused. It seems MF doesn't want you playing with different types of fuses because they want to minimize the possibility of their product destroying your amplifier. Mains fuses are not 100% failsafe; for better protection, circuit level fuses are often used.
Musical Fidelity 550 supercharger monoblock fuse location?
I need help to find the fuse location of these amps, the manual does not show where the fuse are located.Thanks