I want to create a TRRS splitter / joiner that can be used to combine two 3.5mm jacks, one for headphones and one for a microphone, into a single 3.5mm TRRS male jack. It'll use the CTIA standard so that I'd be able to connect it to a standard PC or mobile phone headset port.
The issue is that the sort of microphone I want to connect (here's an example) uses a TRS jack, and with a TRRS cable only one contact / wire is used to carry the mic signal (which with the CTIA standard is the sleeve). I'm fairly certain it's an electret microphone, it's mono, and it's unbalanced.
What do I do with the ring contact on the mic's TRS jack?
Here's a (crude) illustration of the issue:
Perhaps I connect both the mic tip and ring to the TRRS sleeve? Or maybe the mic ring should be connected to the ground?
Best Answer
The de facto standard for PC microphone power and audio is commonly called “plug-in power”. You can find some documentation of it using that search term.
In practice, since electret microphone capsules have only two contacts and expect the power combined with the audio, tip and ring are often shorted together by the wiring of the microphone.
Some sound cards support stereo microphones by using tip and ring as two channels each with combined power and audio; this is backwards compatible since the microphone will get power from one channel and send audio to the other or both.
In your case, since you have only the two wires of a TRRS headset connection's microphone circuit, you have two options: