This module was originally created by @magura320 for OnePlus 3T. I have used this on OnePlus 3T and now ported to OnePlus 5. This is my first mod on XDA, so please be patient with any issues. Let me know if I have missed any credits and would be happy to add them.
Please visit OnePlus 3T thread for OP 3T downloads..
OP5_Stereo Sound Mod.zip - Install the Mod using custom recovery like TWRP.
OP5_Revert to Stock Sound.zip - Revert the mod using custom recovery like TWRP.
OP5_Stereo Sound Mod_Magisk.zip - Install the Mod through Magisk (No revert step as of now).
mixer_paths_tasha-stereo.xml - If you don't want to install the above mods, you can just replace mixer_paths_tasha.xml in system/etc folder with attached file. (Remove "-stereo" from attached file).
mixer_paths_tasha-stock.xml - If something goes wrong, you can just replace mixer_paths_tasha.xml in system/etc folder with attached file. (Remove "-stock" from attached file).
@magura320 - For original mod creation
@SpasilliumNexus - Magisk mod for OnePlus 3T