How to Wire a 3 Stereo Audio Plug | It Still Works The 3 stereo audio plug is the standard jack for MP3 players and other portable audio devices. This mini-plug was developed because a lot of modern equipment cannot accommodate standard 1/4-inch jacks. The small size of the 3.5mm plug makes wiring one a bit difficult, but with practice and the right soldering 3 Audio Jack (TS, TRS, TRRS Type Audio Jack) Wiring Dec 10, 2018Brief Description. Now-a-days 3.5mm is the universal audio jack size to be found in Smartphones, PC and Laptops. Also, for hobbyists 3.5mm audio jack is a useful components for projects that plug into headphone jacks.