@alfkil
Yes, the sb live is a audigy card but the sb 128 is not (I think there is model called sb 128 live which is a renamed sb live card).
What are you plugging into the yellow connector, it sounds as if it is the wrong connector for whatever you are plugging into it.
The one closet to the d-sub is rear-out (powered speakers or amplifier), the next one up is line-out (amplifier, powered speakers and headphones), then mic-in, line-in and digital-in.
Try this link for a manual.
https://www.manualslib.com/manual/1324152/Creative-Ct4760.html