Hi, I'm using a soundblaster 5.1 with mythtv.

I can get sound when I play mp3's through myth, but there is no sound at all from the TV. Has anyone got ideas?

You haven't provided enough detail to for us to make reasonable guesses let alone give you a good answer.

What version of KnoppMyth are you using?

What kind of capture card are you using?

- PVR-[23]50? You've probably got something muted or misconfigured in the setup screens.

- BTTV? Have you jumpered it's audio output to the sound cards input?

Look at my signature block below. You should provide at least that much detail about your hardware setup when asking question like this.