I want to connect line-out of a device to the microphone input of an Android phone, a Xiaomi Mi 4X. Then I can record and live stream from the phone.
If I simply connect line-out left/right (red/white) to the sleeve and ground (yellow) to ring 2, then the microphone does work. However, the phone will still use the internal microphone in addition. This does not happen when I use a headset (Bose QC25). So apparently additional wiring is necessary, but how?
I also tried connecting the (unused) headphone connectors to ground, using a 220 Ω resistor. These are ring 2 and the tip. The idea is to match the 32–300 Ω impedance in the Android 3.5 mm Headset Jack Device Specification, hoping that this will make my adapter be recognized as a regular headset. It did not help.
Best Answer
I measured the resistance between the sleeve and ring 2 on my Bose QC25 headphones: 5.6 kΩ
This led me to adding a 5.5 kΩ resistor to my plug, and it works:
Notes:
Rings 3 and 4 are intentionally left unconnected. I don’t need headphone output.
With another headset that I tried, the phone, a Xiaomi 4X, did not detect it properly. That headset did work on another phone. There seems something odd about the Xiaomi 4X.