in an active equalizer for selectively boosting or attenuating predetermined frequencies of audio or other electrical signals , and which comprises an inverting amplifier having an inverting input which receives the input signal through an input resistance and an output connected with the inverting input through a feedback resistance and at which the equalized output is derived , and an active filter for determining the frequencies to be boosted or attenuated ; there is further provided a change - over switch having a boosting position in which the input signal is applied to the active filter , an attenuating position in which the output of the inverting filter is applied to the active filter and a neutral position , and a potentiometer connected between the output of the active filter and the inverting input of the inverting amplifier and being operable in concert with the change - over switch for determining the extent to which the frequencies determined by the active filter are boosted or attenuated .