Method of controlling a pulse tube cryocooler in which the power input to the acoustic source is varied to maintain temperature of a refrigeration load or a temperature that is at least referable to the temperature of the refrigeration load, at a set point temperature. Additionally, the impedance of an inertance network of the pulse tube cryocooler is also adjusted to obtain a maximum cooling power to the refrigeration load at the particular temperature as sensed and the particular power that is being supplied to the acoustic source.