Modern electric guitars are used all sorts of devices that change the sound of the instrument. It is very popular so-called “distortion effect”. Its essence is that the primary sinusoidal guitar signal is subjected to restriction at the top and bottom, which leads to the emergence of a large number of odd and even harmonics. The scheme of such things published in the Bulgarian magazine “Young designer”.
Turning on the toggle switch ЅА2 cause distortion of the signal with different predominance of the even and odd harmonics introduced by variable resistor R6. The degree of distortion adjust the variable resistor RZ. In the upper position of the switch ЅА1 to play the guitar without the prefix.
Indicated in the diagram, the transistors can be replaced by similar domestic, for example КТ342Б, КТ342В.