Existing papers on active control of combustion instabilities (AIC) mainly deal with combustion systems for gaseous fuel, with loudspeakers serving as interference sources in the combustion process. In this paper, an actuator for liquid fuel is described, which makes it possible to influence combustion actively within a broad frequency range. The structure and function of this control element, called piezo actuator, is described more closely. In particular, the transfer function between excitation of the actuator and the modulation of the fuel how rate is dealt with, because it provides clues as to how the modulated fuel how rate can be used for attenuating oscillations by active control. The additional use of the acoustic resonance in the fuel supply leads to an enhanced effectiveness of the piezo actuator. The performance of the actuator is demonstrated on a diesel-oil-based turbulent laboratory burner exhibiting strong self-excited combustion oscillations. A reduction in the sound pressure amplitude of up to 40 dB is obtained.