Abstract: In a sound system having a sound source for generating sound signals, a low-impedance amplifier for amplifying the generated sound signals, and high-impedance loudspeakers for reproducing audible sound from the amplified sound signals, an impedance conversion device having a step-up transformer section is disconnectably connected between the amplifier and the high-impedance speakers. The output side of the low-impedance amplifier is also connected directly to low-impedance loudspeakers. Thus the sound system can be operated to selectively broadcast either monaural sound or binaural stereo music of high quality.