It is shown that, in a delay line using Rayleigh waves, the amplitude and the delay as functions of frequency can be controlled independently of each other. The frequency/delay characteristic is controlled by the spacing of the fingers along the comb transducer; the amplitude response is controlled by varying the length of the fingers. This principle is illustrated with an example of a dispersive line where both the spacing and the length are varied to reduce the sidelobes to a level 28 dB below the main peak.