Disclosure: I received a free AGPTek Rocker audio player at the DC area Head-Fi meet.   I used my Koss KSC-75 ear clip headphones to review this audio player. I compared it against the audio output of my Samsung Galaxy S7 audio output using USB Audio Player Pro and my venerable Sony Walkman NWZ-S736F audio player. I used FLAC files for my S7 and the AGPTek Rocker that were ripped from CD. My Sony doesn't support FLAC, so 320kbps CBR MP3 files were used instead. No equalization was used during the review. I only had a free 8GB microSD card on hand...