originalhandy,
Try as Duvid uggests , and ensure that if there is an 'external amplifier' label to ensure its moved to the active side, and double check that there are no muted or volume reduced sections.
If this all look ok then try going to the configure your desktop icon (KDE Control centre) and locate the multimedia tab and highlight the listed sound system one by one, and test.
Another possibility is that if you have an 'addon sound card' to ensure that the onboard audio is disabled
If none of these suggestions work then post back and we can look at alsaconf and kernel modules etc
Jase