The invention relates to a device (12) for amplifying audio signals, comprising an amplifier (121) adapted to receive a first signal as input and to output a second signal capable of powering a loudspeaker (R L ), control means (122) configured for detecting the current and voltage of the second signal and for controlling said amplifier on the basis of the voltage of the first signal and of selection information (k) that allows selecting whether the amplifier (121) is also driven on the basis of the voltage or current of the second signal, tuning means (123) configured for changing the output impedance of the device (12) so that, when the first audio signal has constant frequency and voltage, the voltage of the second signal will be independent of the selection information (k) used by the control means for controlling said amplifier (121).