This happens exactly the same for instance on Mac or Windows with BT headphones, it's simply a fact of Bluetooth. If at any point you open an app that accesses

This happens exactly the same for instance on Mac or Windows with BT headphones, it's simply a fact of Bluetooth. If at any point you open an app that accesses the microphone of the earbuds / headphones, the format will downgrade from high-quality, playback only BT profile to a low-quality duplex profile. There's no high quality duplex audio profile in the Bluetooth protocol yet afaik, and certainly not implemented by any vendor. Just do t use Bluetooth if you care about sound quality is the answer.