Equalizer APO - A system-wide equalizer for Windows 7 / 8 / 8.1 / 10 with channel remapping/copying capabilities
PulseEffects - Limiter, compressor, reverberation, stereo equalizer and auto volume effects for Pulseaudio...
FxSound - Clearer Sound for Your PC. The new FxSound boosts your sound quality, volume, clarity and bass.
Equalizer Pie - Equalizer Pie is a free audio manipulation application for OS X.
DeskFX Audio Enhancer - Download this free audio utility to refine, control & perfect the sound playing on your computer. Live audio effects include amplify, equalize, reverb, chorus and more. Studio quality sound from your PC or Mac in pure digital.
JamesDSP for Linux - An audio effect processor for PipeWire and PulseAudio clients.