This Baxandall tone control was obtained in an Argentine publication from the 70s. The circuit uses BC558 transistors and has a good gain, being powered by a 12V source. Electrolytic capacitors can be of close values because the ones used are of values that can already be found in the specialized market. Input and output cables must be shielded. Changes to the values of some resistors may be necessary, as the original design is for germanium transistors.