Hello,
No. For current release the Audio input from an external device is not supported.
So, what you need to do is connect the Audio directly onto the LCD TV Audio input or to a some external receiver.
So whenever you set the Capture Card to show (via timeline) you should mute all other sources (videos etc..) and so the only sound will be the external TV Speakers. This should be sufficient in most cases as it allows you to control the Audio volume using the remote control of the LCD TV.
Always glad to help,
Sean - MediaSignage.com