@chloe-zhao -thanks for the response.

Yes- I tried changing to HDMI 2

No - I can't download the audio sources, but it can be re-created easily:
1 - plugin either an ipad pro and play movies from iTunes, or
2 - plugin an amazon UHD fire stick and play any movies - with the audio set to anything by stereo
3 - plugin any generation of apply tv and play a movie

All have the same effect and the audio is just crackles, hisses and pops.

Thanks
Dave

Hi - just got mogo pro and any 5.1 audio source through hdmi just results in buzzing and crackling - have tried; iPad Pro, Apple TV and Amazon Fire stick. The fire stick works ok if you switch sound into stereo, but even then it sounds really bad.
Did I get a back one, or is this a known problem - hopefully with a known fix?

Thanks

Dave