You must download 2 files and replace it in /system/etc folder.
It works only on Cyanogenmod 12.1 and 13. If you want you can download latest alpha build of PowerAmp and try it out. This mod allow you to enable Hi-Res output on Headphones.
If you listen MP3 files with Hi-Res output enabled it will be very bad audio quality. Use it only with 96kHz/24b Flac files or better.