The invention relates to a tuner for converting a radio frequency signal into an intermediate frequency signal, said tuner comprising a voltage converter supplying a control signal, a mixer associated with an oscillator which is voltage-controlled by said control signal.The invention is characterized in that said voltage converter comprises: an auto-oscillating circuit generating an alternating voltage signal of a variable level, rectifying means for supplying a direct voltage signal of a variable level based on said alternating voltage signal of a variable level, an additional circuit for reducing the variations of the attenuation coefficient of said auto-oscillating circuit, said additional circuit receiving said direct voltage signal of a variable level and supplying said control signal. The invention provides an inexpensive solution having an improved performance in terms of spectral purity, ease of implementation and stability of control of said intermediate frequency signal.