eqMac 2 - The open-source macOS audio optimizer 🎛️
Equalizer APO - A system-wide equalizer for Windows 7 / 8 / 8.1 / 10 with channel remapping/copying capabilities
SoundSource - The sound control that should be built into MacOS
FxSound - Clearer Sound for Your PC. The new FxSound boosts your sound quality, volume, clarity and bass.
Noizio - Feeling that the noise of the big city is too much for you to bear?
Boom 2 - Boom is a simple volume booster that lets you boost the volume of your Mac and your music files.