Simple additive mixers use Kirchhoff's circuit laws to add the currents of two or more signals together.
When two different signals are applied to an input of an operational amplifier (assuming the amplifier input impedance
is much higher than the source impedances of the two signal generators) they will add at Vin Junction
point shown on the schematics diagram below.
The amplifier gain is 200
Shown below is the resultant output waveform.
The following image is taken from o-scope simulation in MultisimBLUE
The simulated waveform can be played on a PC speaker. Double click on the speaker symbol.
Use "Multisim schematics file with audio output" example below. Run the simulation for a few seconds, then press
"Play sound button" and you should hear the mixed simulated sound.
Used useful links:
LM386 simulation model: http://ecee.colorado.edu/~mathys/ecen1400/Software/LM386.cir
Create LM386 in MultiSIM BLUE: http://ecee.colorado.edu/~mathys/ecen1400/Software/CreateLM386.html
Multisim schematics file.
Multisim schematics file with an audio output.
Used MultiSIM BLUE for simulation.