Stereo is 1 pin, if you look on the pin there are 2 lines that go around the pin thats why if you pull it half way out you can hear out of one speaker and not the other. if you have 2 pins for your speakers the other set if for the Rear speakers and you can even have another pin for center, and so on if you have 5.1, 6.1,7.1, etc. mics have one pin.