General newbie breadboard wiring question

Newbie question here. I am using an Arduino Pro Mini and have tones playing through pin 8 connected to a headphone jack to 32 ohm headphones (with a 220 Ohm resistor). Both “ears” are in parallel from the single pin. It is working fine.

I also have sound come from a separate mp3 player (not going through the Arduino at all) and I would like to have that sound playing through the same headphone jack. I just can’t figure out the way to wire it up to achieve the result.

Any help would be greatly appreciated :slight_smile:

You need a mixer. That could be as simple as 4 resistors but I recommend you find a small amplifier with 2 inputs.


Thank you MorganS for your answer, I appreciate you taking the time to help out. Of course, a mixer makes sense. I would be very curious to know how 4 resistors would work, could you explain briefly or point me in the direction of a tutorial? I will Google as well.


You already know that you can’t connect 2 outputs together. But you can connect them with 2 resistors in series. Then the middle of the 2 resistors is an “average” of the two voltages.

I’m assuming stereo, so you need 4 resistors. Experiment with different values or with potentiometers to change the mix.

The problem with this is most of the output power is lost in the resistors. It might work for headphones but certainly not for full-size speakers. In that case, you need to amplify the mixed signal from the resistors. Any amplifier will do.

I did find a tutorial explaining resistors in series and parallel and was able to figure out the problem. Thank you MorganS for pointing me in the right direction :slight_smile: