You have a dedicated sound card then.
Printable View
Are them connections on the "main" motherboard? i.e next to your onboard video output or further down in the case?
EDIT: I really should reload the page instead of sitting on it for half an hour.
Erm, does the jittering happen all the time?
http://images.marketworks.com/hi/58/...gx280_back.jpg e.g. the colourful bit or further down?