Scratch is the sharp noise that appears in the speaker when a disc has scratches or imperfections that generate high-pitched sounds, similar to what is obtained by scratching objects. The displayed filter eliminates these noises, thereby facilitating achievement of the purest sounds when a disk is being recovered with its program recorded on other media. The operational amplifiers TL072 are 741 or equivalent and the cutoff frequency depend on the components. The power supply must be symmetrical. The circuit cut-off frequency depends on the components according to the following table:

Cut Frequency C R
10 kHz 1n5 10k
7,5 kHz 1n5 14k
5 kHz 1n5 22k