I have 2 QN90A 50" TV's they are an amazing tv. I like all the features on them. I have some songs on a hdd that I sometimes play on the TV's. They play fine through the normal TV speakers on both TV's.
I have 2 bluetooth headsets, the Sony MK4 and MK5. If I connect them to either of the two TV's they play sound perfectly if I am watching say something on my Sky box. If I then switch over to the USB drive, the sound comes out very crackly. Switch back to the sky box on the hdmi port and they are fine.
I can replicate this on both tv's with both headphones. It is only when playing things via USB. I have a WD USB powered drive.