PS. I have mentioned several time in earlier posts, on LG phones using UAPP we can achieve the 4th filter mode: 'no filter'. By pass the filters (Short, Sharp, Slow).
This just feels like Cayin RU6's 'NOS' mode.
Cayin RU6 thread:
https://www.head-fi.org/threads/cayin-ru6-r-2r-usb-dongle-dac-with-head-amp.960113 people's preferrence between NOS mode vs OS mode is an on going topic in the thread.
How: in UAPP settings -> Internal HiRes audio -> HiRes driver flags -> check 'Direct' or 'Raw'.
What's special about Cayin RU6's NOS mode, or LG's 'no filter' mode: Better spatial, bass, more details. To me, this mode is the most honest and unprocessed playback of every bit of information in the recording. For great, analog recordings, this mode is the best. For bad, digital recordings, this mode can reveal 'digital feeling'.
LG's filtered mode (Short, Sharp, Slow) are just like Cayin RU6's OS filter modes, they make recordings 'seem like' more analog, more fine grained smooth details, but after long listening the brain always feel something is 'wrong', 'nausea‘. The filter's processing can make bad, digital recording sound better, but for good recordings they are not necessary.