This tutorial explains how to enable the Equalizer feature on the mobile version of VLC. Several presets (Bass enhanced, Treble, Live, Classical...) are available, allowing you to fine tune your audio settings based on your personal preferences.
Open the VLC app and tap on the menu key (3 horizontal dots located at the top right corner) > Equalizer:
Toggle the Equalizer feature On:
You can choose a default preset and edit it: