Get it, tecos.
Please go to Settings->Audio, set "HDMI" as audio ouput and try the two cases below.
1.Mark "Dolby Digital(AC3) capable receiver", "DTS capable receiver" and "TrueHD/DTS-HD capable receiver". In this case, your amplifier will decoder the audio stream and play it.
2.Un-mark the three options above. In this, DVDFab mediaplayer will decoder the audio stream and passthough the decoded audio stream to your amplifier. Your amplifier just plays it.
What's more, I doubt it may be the external driver issue in mac os. Please try some BD/DVD iso in your local disc.
Wish it helps.