Is it true that if I have an astro mix amp, a fiio e9 DAC, and AKG 702 that I should not turn on Dolby 5.1 on the mix amp?  I think I am noticing a huge difference in the quality of the stage without the 5.1 on.

I want to use an external mic on my XBOX One.  I am connecting my AKG 702 to my XBOX One with an Astro mix amp and a Fiio E9. So I have the Astro Mix Amp connected to the XBOX One via Optical cable and then from the Astro Mix Amp to the Fiio via the 3.5 mm output of the mixamp to the 3.5mm...

I can't figure it out.