An electrohydraulic shock-wave therapy apparatus comprising a variable voltage source and a controller that controls the voltage source for accurate adjustment of the shock wave pressure. The invention, in various embodiments, also includes various methods, optionally closed loop as well as open loop based, for determining the shock pressure while compensating for burnout and or erosion that normally suppress the pressure after some thousands of sparks. This way the effective lifetime of the electrodes is dramatically extended. The control is further used for significantly increasing the effective therapeutic area of the apparatus by adjusting the shock pressure value close to the maximal safe value.