Standard for auxiliary/CD inputs on a soundcard

[izua]

I'm looking for the pinouts of the jumpers on a C-media 8738 soundcard. I believe there is a standard, though.
The jumpers in question are the audio cd input and the aux input.
I can't find the ground - when i touch each of them, i see the mains hum on the scope, but it reacts to any of the three wires.
Plus, there's one more weird thing - There are 4 pins on the pins, but the cd audio cable has only three (missing second, or third, depends on how you look).

Thanks.

 

[banjo]

I think you would see the same hum on the scope if you touched the probe to the computer's ground as well. The computer is full of noise, the scope method does not tell you much.

With the computer off, take an ohmmeter and check the resistance from each of the four pins to ground or the chassis. Two pins should have a low resistance. These are the ground pins, the other two are the signal inputs.

Your cables only have three pins because the ground terminal is redundant. If you look closely at the cables, you will see that the ground shields are wrapped together and connected to the same pin.