Blue Tooth Issue:
Using a pair of Sony WH1000-MX3 headphones in BT mode.
Certainly, I don't understand BT but the FiiO BT signal obviously has some embedded volume signal that it sends through BT because the volume of the headphones change when the volume on the M9 is changed. The M9 needs to have the scale of this signal shifted upwards. Currently, the scale is so low most burned 16bit 44.1 CDs it leaves very little headroom to increase the volume.
- Fiio M9 - Volume of the sound can be control by BOTH the M9 AND the headphones. This isn't a major issue. However, the REAL problem is even with the Fiio Volume set to 120. I sometimes have to turn the headphone volume up to nearly 95% to obtain a "loud" listening level. This seems wrong.
- iPhone 10R - Volume of the sound is "linked" between the phone and the headphones. However, when the volume is increased (on either device) it usually only needs to be set to about 60-70% to achieve a "loud" listening level. This seems more in line with what would be expected intuitively.
But when you using the iPhone, the Bluetooth codec is not the same one as using in M9, right? We did not receive similar feedback from other users using WH1000-MX3 with the M9 currently. You may try to do a factory restore and change another Bluetooth codec in the M9 for checking again?