AUTOMATIC LOUDNESS CIRCUIT

PURPOSE:To attain sound volume correction of a low frequency band at the sound volume adjustment by inputting an output signal of a 1st electronic volume for adjusting sound volume to a 2nd electronic volume and extracting a difference of the input and output signals of the 2nd electronic volume. CONSTITUTION:The output of the 1st electronic volume 3 is inputted to the 2nd electronic volume 5 from a line 4. A 1st subtraction circuit 10 subtracts the output V2 of the 2nd electronic volume 5 from the output V1 of the 1st electronic volume 3 from the output V1 of the 1st electronic volume 3, leads out a difference signal (V1-V2) from the line 11 and gives it to a serial resonance circuit 12 via a resistor R. An output from a connecting point 13 of the series resonance circuit 12 is given to a 2nd subtractor 14, which gives the output of the 1st electronic volume 3 to the line 15. Thus, when the attenuation of the 1st electronic volume 3 is changed, the deficiency of low sound only at the small sound volume is corrected.