Audio Mixer 3to1

I feel your connecton for potentiometers is little bit unusual. Do you have some kinds of special purpose? Especially, your connecton of summing stage might cause the balance of inputs moves by the position of potentiometer.

Nothing special, just a minimalist circuit. I dont see how they could get unbalanced. Those pots are to adjust the gain of each mono channel and how much each contribute to the final output. It's a little bit crude, but can be done with only one quad opamp ic, pots, caps and a few resistors.

Please check currents of three 33K resistors, and check how they change by the position of potentiometer of the final stage. This means the each load impedance of the first stages is dynamically moving on your circut, by input voltages of other channels. When the resistances from the first stages to the second stage of three channels, including 33K ohms, are completely same, this may not be matter. But otherwise, it may cause what I said. Your mixing stage loocks like a passive mixer and an added amplifire. I think connecting direct the point of 33K ohms to the (-) input of the final stage, which is kept to GND level by imaginary short, is better. ...Of course, I know your connecton effects changing the taper of resistance of potentiometer.

Changed it a lot. Takes more parts, but should be a little bit better now...