This one is a 10 band graphic equalizer circuit based on TL074 low noise JFET op-amp. As shown in the diagram, there are 10 same units that only differ in capacitance values of capacitors which determine the frequency band of each filter. The potentiometers adjust the predetermined regions of frequency in each unit. The center frequencies of the regions are; 32Hz, 64Hz, 125Hz, 250Hz, 500Hz, 1kHz, 2kHz, 4kHz, 8kHz and 16kHz.
RV resistors prevent the frequency interference. But if any interference occurs, the filters act as cut-off to an unrelated signal.
The components must be high quality and have low tolerance. The resistors must be metal-film type.
To use this graphic equalizer in stereo mode, you must construct two of them with matched components so there won’t be any difference in regulation of frequency bands.
S1 switch bypasses the graphic equalizer and then the circuit gives an output of flat response.
The graphic equalizer must be connected between a preamplifier unit and a power amplifier unit.
The components list is given in the schematic page.