Wire mono microphone to stereo jack?

Question

I have a microphone with 2 wires, and a cable jack with 3 wires. How do I wire them together?

Basically i took apart a usb headset and got a microphone with 2 wires, then i cut a jack cable 3.5mm. I'd like to rebuild the microphone if it's possible, to use it on a pc

I'm not good on these things, but I think the mic has a positive and a ground wire, while the 3.5mm cable has a positive a negative and a ground wire.

-I'm sorry, I realized now it is offtopic, but this had to be something like a free time project. It's the first time i try something like this, so after looking for some help on the net for some time, I read something similar on this website. I was so frustrated that i just subscribed and typed, without reading, so please remove my question if it's an off topic :(

Answer 1

Without knowing what kinds of connections you are dealing with, it's not really possible to answer your question directly. There are a few different reasons you could have 3 conductors on the plug. It may be that it is stereo, it may be that it is balanced and on consumer gear, it may be that it supports both a microphone and a mono audio output at the same time.

Generally speaking, stereo mics are pretty rare. The vast majority of microphones are mono and when you want stereo, it's typical to hook up two mono microphones. Unless you are dealing with a cellphone, it's also pretty rare to have a mono input and mono output in the same connection.

If it is a balanced input, then you will need to make a balanced signal to feed to it. You can do this with a device called a direct box which will take an unbalanced signal and turn it in to a balanced one. In the case of an unbalanced mic, you're normally best to switch to using a balanced mic rather than an unbalanced one, since unbalanced mics are normally consumer quality.

If this actually is a production related question, then if you can post images of the connectors you are talking about, we can give a more definitive answer.

Answer 2

You want to build an electret microphone to use on a PC. (This is the typical microphone type found in consumer-level USB microphones, using small microphone capsules of typically 5-10 mm diameter. If your capsule is rather 20-40 mm diameter, it is probably a dynamic microphone and needs a different connection than explained below.)

So first, look up the type and pinout of a microphone jack on a PC (here; sorry, German source). The type is a 3.5 mm audio jack with three terminals ("TRS") for an unbalanced mono signal. The pinout uses the consumer device microphone pinout, as follows:

• tip terminal: microphone signal
• ring terminal: supply voltage (+3 V to +5 V)
• sleeve terminal: ground

To connect an electret microphone to this, which has two terminals, follow the pinout of these devices from here:

• Tip and ring shorted together and connected to one microphone wire. This leads to a microphone signal pin that also receives supply voltage from the jack's ring connector. This is intended and called audio line voltage, or "Tonaderspeisung" in German (details).

• Sleeve connected to the second microphone terminal.

It does not matter which microphone terminal you connect to which of these pins on the 3.5 mm audio plug, as polarity on electret microphones is not important. They are basically variable resistors, and polarity does not matter for resistors.