How to build Variable High-Pass 20HZ to 200HZ Filter

Description

A simple circuit, High-Pass filter, variable between frequencies 20HZ until 200HZ, useful in a lot of cases elaboration of sound signals. The regulation is achieved with the double potesometer 47KΩ and the frequency response in his two extreme places, appears in the schematic.

Circuit diagram

circuit from http://users.otenet.gr/~athsam/variable_filter.htm