Disclosed is an electromechanical generator for converting mechanical vibrational energy into electrical energy, the electromechanical generator comprising: a mass resiliently connected to a body by a biasing device and adapted to oscillate about an equilibrium point relative to the body with an oscillation amplitude, a transducer configured to convert oscillations of the mass about the equilibrium point relative to the body into electrical energy, and a resilient device disposed between the biasing device and one of the mass and the body, wherein the resilient device is configured to be deformed between the biasing device and the one of the mass and the body only when the oscillation amplitude exceeds a predetermined non-zero threshold amplitude. The resilient device may comprise one of a helical spring, an O-ring and a spring washer, such as a Belleville washer, a curved disc spring, a wave washer, and a split washer.