I have one of those average cheapo computer microphones that connects into the sound card via pink 3.5mm jack.
I wanted to find out how much voltage can I expect from it, to get a ballpark value I could use for my opamp noise detection circuit.
The microphone works fine when connected to the PC.
And so I hooked the microphone to a scope, expecting to see my voice visualized on the screen when I talk, but all I am getting is a flat line.
I looked at how other people do it, and they merely just hooked the scope directly to the jack of the microphone, just like me, and it is working just fine for them.
So, what am I doing wrong here?
Thank you
Best Answer
An electret microphone requires a DC bias current sourced from typically 5 volts through a 4k7 resistor to the microphone. This is a normal feature within sound cards for the microphone input and you may not be aware of that: -
If your microphone jack plug has three connections on it one may incorporate an internal resistor already.