Compressor makes signal/sound volume stable, doesn`t let it higher or lower from the level you set. Limiter prevents volume being too loud, but lets volume go lower from the level you set. Equslizer is just leveling of frequencies. But the more of the equipment you add the more S/N ratio (sound to noise ratio) will be on the noise ratio, every equipment adds a little noise to the audio, while at the same time imroving the sound.But the noise.. You probably won`t even hear it unless you boost volume too high without playing music or voice through your sound system.