roby said:
sorry but i dont know much about electronics i asked if u could describe how does it works...didnt want to impress u
looking 4 help....
OK.
An opamp is an 'operational amplifier', they were originally designed for analogue computers, but with the advent of IC's have become a popular electronic component.
U1 is configured as an 'adder', originally used to add voltages (numbers) together in the analogue computers - in this case it's used to 'add' (mix in audio terms) the three signals together. The three input controls adjust the percentage of each signal added to the mix.
U1 is followed by passive tone controls, for bass and treble, being passive these lose considerable amounts of signal, so U1 needs enough gain to overcome this.
The last section, U2, is simply a buffer, which gives a low impedance output to feed to an amplifier or recorder. Without this the fairly low input impedance of the following circuits would load the tone controls, and stop the circuit functioning correctly.
If you actually want to build a small mixer like this, let us know and we can make suggestions.