To minimize vibration without the need for a separate vibration balancing unit.

A stator 230 of a linear electro-magnetic-mechanical transducer coupled to a Stirling machine is mounted inside a casing 238 through an interposed spring 250 and the stator is reciprocated to flex the spring during operation. The natural frequency sof the stator is equal to a mathematical expression [p the square root (1-p/Kp)], where pis the spring constant of spring coupling between a displacer and a piston and Kpis the spring constant of spring coupling between the piston and the casing. The natural frequency pof a power piston 214 is maintained equal to the operating frequency oof the Stirling machine and the linear electro-magnetic-mechanical transducer. When the variations in the average temperature and the average pressure of working gas cause substantial variations in the resonant frequency pof the power piston 214, vibration balance is kept by means for compensating for those variations.