Low volume when loading external audio file in VD

Hello,

When i load an external audio file .ac3 into a video loaded inside virtualdub, although the original file audio is loud, it becomes inside vd very low.
So when i save the avi as "direct stream audio" i get the same loud audio but the problem lies if i do full processing for the audio.

the result of the full audio processing is a low volume audio track as i mentioned above.

What's wrong? why i can't get the same audio after full processing?

Thanks.