As you may know, the EU limits the Musicvolume your phone can put out. For some people like me, it is just too low, i can hear traffic when i listen to music even with decent in-ears.
However, thanks to @Paolo83 there is a solution to this problem.
What you need:
P9 Lite on B370/B380
Root and an Root File explorer.
Note: Single sim devices are Venus, Dualsim devices are Venus2.
Sidenote: Venus and Venus2 are Huaweis company internal codenames for single and dualsim VNS-L21 and L31 if you didnt knew.
Step 1: Navigate to /product/etc/audio/hi6402mixer_volumes###
Step 2: Search for the file " mixer_volumes_VENUS_ce" file on singlesim devices, and for " mixer_volumes_VENUS2_ce" on dualsim devices.
Step 3: Open the file in an text editor, and search for this part
<path name="media-headphone" > <ctl name="S1 IL PGA GAIN" value="0" /> <ctl name="S1 IR PGA GAIN" value="0" /> <ctl name="HPL PGA GAIN" value="10" /> <ctl name="HPR PGA GAIN" value="10" /> </path>
Note: You dont have to use the 28 value. If 28 is too loud for you just use a lower value like 15.
Step 4: Reboot and thats it!
Warning: Values above 20 are EXTREMELY, INSANELY loud, do not hear music at max volume for extended periods of time.
Credit goes to: https://forum.xda-developers.com/sho...&postcount=416
Again, i am sorry i couldnt give credit where credit is due earlier.