Abstract: A method of improving the frequency reproduction at frequencies higher than a certain break frequency (fs) of a bass amplifier known per se within the audio frequency range. The amplifier has a low-pass filter portion (ACE1) and a power amplifier portion (EF) with a current feedback portion (ACE2) in order to get a negative output impedance against the loudspeaker. According to the invention high-pass filtration is carried out from the break frequency (fs) and upwards to about 20 kHz of the signal coming to the amplifier and thereafter a phase shift (.rho.) is carried out so that a cophasal state is obtained at the break frequency (fs) before the power amplifier portion (EF).