Abstract: A sound detection system of a musical instrument with vibrating parts includes at least a pair of sensors and a preamplification unit for processing the signal output from the two sensors along respective channels. At least one of the pair of sensors is a piezoelectric transducer and the other one of the pair of sensors is a different-type transducer. The preamplification unit includes, for each channel, an input stage, including an amplifier circuit and an equalization circuit, and an output stage including at least a weighted adder circuit and at least two volume controls with arbitrary logarithmic response curve. At least the input stage for the channel of the piezoelectric transducer is a charge amplifier circuit and at least one of the other input stages can be configured both as a charge amplifier and as non-inverting amplifier with high input impedance. The equalization circuit includes an RC circuit.