Power supply units e.g. in network operated loudspeakers are tailored to peak values that are reached only relatively rarely and then in pulses. With an intermediate storage of electrical energy in an intermediate circuit energy storage element it is possible to provide a significantly higher amount of power at least for a short period of time. The intermediate circuit energy storage element may be a capacitor or accumulator, for example, which is connected to an intermediate circuit voltage that is higher than the input voltage, and that is generated by an upconverter. A downconverter generates the output voltage of the power supply unit from the energy stored in the intermediate circuit storage element. The output voltage of the power supply unit is used as power supply for an audio amplifier. The power supply unit may provide for a short period of time a higher current or more energy respectively than the actual energy source, for example the network node. Correspondingly, the device operated with the output voltage of the power supply unit, for example the audio amplifier, can have a significantly higher effective power than previously possible for the short period of time.