2×10 Band Stereo Graphic Equaliser circuit diagram

This circuit must be connected before the amplifier circuit. For maximum performance, you may use high quality electronic component such as metalfilm resistor, MKM capacitor (nonpolar), tantalum capacitor (bipolar). You may replace the power supply module with regulated and stabilized power supply or just add IC LM7815 after R35 and IC LM7915 after R36.

With good components and good power supply, then the sound quality will get better.