We found this circuit in a publication of 1990. With the changes it can be mounted easily today. With it we can control bass and treble with an additional system of medium control. The circuit can be implemented with other equivalent JFET operational. The power supply must be symmetrical and input cables and output cables must be shielded. Control pots should all be linear. The symmetric power supply must have excellent filtration. Consumption is a few tens of milliamps.
