|1||USB +5V in||USB 5V supply - not used in K750|
|2||SP_REF||Reference / GND for handsfree|
|3||Mic+/AUXIN_L||Mic + / AUX in (left)/ short with pin 4 for handsfree answer (*)|
|4||Mic-/AUXIN_R||Mic - / AUX in - (right) / short with pin 3|
|5||DFMS/SP_L||DFMS / Earphones left|
|6||DTMS/SP_R||DTMS / Earphone right|
|7||VIDEO/STB||Video / strobe|
|8||VPPFLASH||short with pin 9 via R=130 Om for handsfree detection|
|10||CTMS / USB DATA+||CTMS / USB+ (data) - not used in K750|
|11||CFMS / USB DATA-||CFMS / USB- (data) - not used in K750|
|12||Charge In||Battery charge (+5V) - not used in K750|
If you want to make a stereo converter with a SE socket, you should use pins 5 and 6. It may not work well with an amplifier due to low output i.e. just enough power for headphones . (May need pre-amp).
To make a stereo-amp using the cell phone you must shortcircuit pins 8 and 9. Then connect the outputs (L) (R) (GND) using pins 5 = (left), 6 = (right) and 9 = (GND).
Sony-Erisson Walkman original handset uses pins 2 (GND), 5 (Left) and 6 (Right).
(*) For incoming call answering short pin 3 and 4
Headset for S302 and similiar phones pinout: R pin 7, L pin 8, pin 11 is GND for both channels and probbably for microphone too. Active gain should be between 50 and 200 for LM386.