An apparatus (100) comprises a signal generator (101) that is set up to produce a digital random signal (191). The apparatus (100) also comprises at least one filter element (102, 121, 122) that is set up to apply a high pass filter and a low pass filter to the digital random signal (191) in order to produce a spectrally shaped random signal (112). The apparatus (100) also comprises a modulator (103) that is set up to apply the spectrally shaped random signal (192) as dither.