In high power amplifiers, when power is switched on, the various stages inside the circuit board take a few milliseconds to stabilize. However, before the circuit stages are able to stabilize, the MOSFETs are forced to conduct instantaneously due to the switch on voltage spike, allowing the full input DC to pass though the connected loudspeakers. The loudspeakers being low in resistance create a momentary short circuit kind of situation causing heavy load on the amp fuses, until they blow.