A device for sample modulating electronic information signals, which includes a pulse position modulating circuit having a first input coupled to receive information signals, a second input coupled to simultaneously receive uniformly spaced sampling signals, and an output for generating thereon in response to each sampling signal an electronic output impulse at a time instant indicating the amplitude of the simultaneously received information signals. Also included is an acoustic surface wave device having an impulse response of predetermined shape and finite length. The surface wave device has an input coupled to receive the impulses from the pulse position modulating circuit for generating in response thereto output signals proportional to the convolution of the impulses with the impulse response. Accordingly, these output signals also are of predetermined shape and finite length, and thus have a highly controllable frequency spectrum.