I think I know how to do this, but I just wanna make sure before I go ahead and start. I'm planning on wiring in a headphone/amp switching circuit to my handheld (a unit running RetroPie), which is on a Raspberry Pi B+. Using this TRS jack as an example, I'm pretty sure I need to wire Terminal 1 to ground (pin PP6 will be taken by the monitor's ground, should I just connect this to a ground in GPIO?) Terminal 2 to left audio souce (pin PP25 on RPi) Terminal 3 to right audio source (pin PP26 on RPi) Terminal 4 to left amplifier Terminal 5 to right amplifier Please confirm or correct me on anything. Last couple of questions: Is there a small board that comes already wired with amps and jack so I can do less work? Does anyone know where I can get some cheap but half-decent amps? Otherwise I may just tear into some old electronics. How do I add volume control? Do I have to go through GPIO?