I have PAM8403 circuit module to drive my two 3W speakers. I want to drive a subwoofer with a different amplifier. I have a 3 inch subwoofer, and I'll get an amplifier for that. My question is how do I get stereo and mono (both) from my source simultaneously? Because if I short the two signals (L and R), or use a resistor and get mono signal, I lose the stereo signal, and signal from the wires becomes mono. I have tried using just L or R after merging the signals, but they do not stay stereo as they were before, so output from the stereo amplifier sounds mono. So what do I do to get separate mono signal from my stereo signals?
I am a beginner at electronics and speakers, so I request you to please construct your answers accordingly so I can understand better.