For the deposition of dielectric thin films, dual magnetron sputtering using AC in the medium frequency range (MFDMS) is widely established. The most obvious advantages of MF over DC excitation is the long term process stability without adverse effects of an insulating coating on the anode and the reduced arcing due to self-extinction at polarity change of the MF power. Also, dense films with fine grains are preferably obtained by MF sputtering. For power supplies in industrial sputter coaters, two substantially different design approaches are available: (1) the resonant output circuit leading essentially to a sine wave excitation and (2) bipolar pulsed excitation with an essentially rectangular output waveform. Yet, little information is available on possible advantages of either power supply type for the process. This paper presents a comprehensive overview of how the choice of power supply may affect the final process. Results are shown on the influence of the output waveform and of the operating frequency on the ion flux and energy to the substrate. Available data on how the coating properties are affected are presented.