I think what Magfan maybe referring to, besides a fused-closed set of relay contacts, is the circuit that controls the protection relay's coil can fault during initial system power-up (or is permanently damaged), which is usually delayed until after full system stabalization (several seconds), thus the "click" sound one hears. Same goes for power-down where the relay drops out first to protect speakers while the amp's voltage drains off slowly.
This is a typical relay controling method in all kinds of equipment, usually triggered by IC's which do fail "open" or "latched".
FWIW,
Frank
This is a typical relay controling method in all kinds of equipment, usually triggered by IC's which do fail "open" or "latched".
FWIW,
Frank