It could be your digital to analog converter. Is it a quality brand/model?

Is there a way you can get an analog output from the sound system?

Mostly, I think you should avoid using the on-board/built-in audio on the motherboard. If the budget allows get a separate audio device. In my experience building audio playback systems for radio stations, on-board/built-in sound was never used.

Also, is it possible you have microphones (separate or camera) too close together, producing phase cancellation?

Giving a quick listen to the clip, there's no low-end at all. The fact that the sound comes only from the center channel of the surround system is also a hint.

It seems very likely that you have a problem with audio phase somewhere. When you have a stereo signal, and one is run anti-phase, it creates this sort of effect should the two channels get summed to mono.

The low frequencies basically cancel, out leaving on the higher frequencies to be heard. I'd expect the level to be quite low also.

You can simplify things by working in mono, but that can be difficult since most gear assumes that there's a stereo audio path.

You might consider installing the Wide Range Audio Meters from Darkwood Designs. They're inexpensive and they include a phase meter, which will show if you have phase problems.

https://www.mgraves.org/...wide-range-audio-meters/

I can certainly endorse the software audio meters from Paul at Darkwood Designs. Given my TV background, I particularly like the BBC-style PPMs, but they're all good meters.

http://stereotool.com

:)