There are actually two separately developed equalizers for pulse audio. I tried the mainstream one but I could not retrieve the gpg key so I am using the "unofficial" one instead. The instructions found here worked OK for me:
I have not found it to add much to the processor usage. If you tell it to "keep settings" and then quit the equalizer, the settings continue to be used for all audio without having to launch the equalizer. To turn it off just launch it again and disable the settings. On my ubuntu laptop I found the "headphone" preset worked better than the "laptop" one.
This equalizer will work with the output of any audio player or audio program you use.
