The circuit constitutes a natural extension of Mic-Line balance unit, but can be adapted to any other audio circuit. It is made up of two units in the series : A) A classic unit bass/ Treble and B) a parametric unit of mid frequencies. Both units can also be used autonomously or each one separately, with the required buffer unit, from previous and subsequent circuits. With the R2 we requlate the High frequencies +/- 18 db/oct at 20 KHZ, with R5 the Low frequencies +/- 18bd/oct at 20 KHZ, with R11 the Mid freq. +/- 15 db/oct and with R10 the center of mid freq. at 200 HZ - 6 KHZ band.