Dave
Honorary Master
Here’s my previous posts about it.

Anyone who thinks their bluetooth audio output is a bit on the weedy and quiet side should check in Developer Options if Xiaomi has set the “let’s strangle BT output to sound absolutely crap” option on (aka the “Disable Absolute Volume“ switch in the Networking section). Switch it to off and reboot the phone.
I can’t believe the difference in sound quality on my Mi10T (especially bass and clarity) and volume now after switching the setting off.
Open Settings -> About phone.
Locate MIUI version (probably Build version on other makes) and tap it 7 times to enable Developer options.
Go to Developer options in Settings -> System -> Additional settings -> Developer options
Scroll down to the Networking section.
Once there, disable (toggle off) the “Disable Absolute volume” option.

