The present invention relates to an apparatus and a method for influencing and/or detecting magnetic particles in a field of view (28). The apparatus comprises selection means for generating a magnetic selection field (50) and drive and receiving means comprising one or more combined drive field and selection coils (441) for changing the position in space of the two sub-zones (52, 54) in the field of view (28) and for acquiring detection signals. A balanced bridge unit (160) comprising inductive or capacitive coupling elements (411, 421) is provided between the drive field signal generator unit (122) and the signal receiving unit (140) as a light-weight, inexpensive and easily implementable solution for reducing the harmonic background.