I understand your problem perfectly, and I also described the solution.
The sensitivity of the Video (AUX) input is 250 mV, your phone can output less than that, which is why it sounds normal, but quieter.
The Phono input, on the other hand, is designed for a TURNTABLE, with a sensitivity of 3 mV (not 250) and RIAA characteristics.
This is not suitable for connecting a mobile phone!!!
It should be understood that even though there are two inputs on the back of the device, consider one of them as if it were not there (PHONO).
I understand your problem perfectly, and I also described the solution.
The sensitivity of the Video (AUX) input is 250 mV, your phone can output less than that, which is why it sounds normal, but quieter.
The Phono input, on the other hand, is designed for a TURNTABLE, with a sensitivity of 3 mV (not 250) and RIAA characteristics.
This is not suitable for connecting a mobile phone!!!
It should be understood that even though there are two inputs on the back of the device, consider one of them as if it were not there (PHONO).