Why are you using UAPP with note 4? Even neutron is better sounding
To my ears on my setup (
Samsung Galaxy Note 3 > Objective DAC > SoundLab Neco V3 amp > MrSpeakers Alpha Dog headphones), UAPP is the best sounding music player for the time being. And I am not alone.
http://www.head-fi.org/t/638387/best-android-music-player-app/240#post_10120655
There is at least one technical reason: USB Audio Player PRO (UAPP) doesn't perform resampling.
Usual music players, like Neutron or Poweramp, have to interface with the Android media player framework which currently performs 44.1kHz-to-48kHz resampling (i.e. only outputs 48kHz PCM streams to USB DAC).
UAPP doesn't have to interface with the Android media player framework for streaming audio via USB: it includes its own USB audio soft driver.
http://www.head-fi.org/t/595071/android-phones-and-usb-dacs/5550#post_10974215