Audio Problems

After converting from AVI to DVD, the video is spot on, but although you can hear and understand the audio, it seems to have a hollow/muffled/basey quality that really detracts from the DVD. Has anyone got any idea as to what may be the cause.

I have a number of codecs installed, and I do not know if any are actually conflicting. Is there a way to ascertain this?

The AVI was downloaded with an audio of AC3 Stereo. I am currently using AC3 filter as the codec, and I am trying to covert the AVI to a DVD with 5.1. Is this possible?

Any assistance would be greatly appreciated

I use the WMA codec, I never had any problems with it and I’m running a pretty out dated sound card.