I am writing this review
1) to say "Thank you" to the one who did the "remastering" and
2) to tell those seeking a tool to amplify the sound on a given web page that my vote goes to this add-on resource.
FYI, I have found the version from a year ago was extremely helpful when listening to recordings of soft-spoken speakers. I have regarded this add-on as a treasure, lost for several months and now found again. When it was gone, I tried a similar one, but that one only worked when audio was combined with video and after a while that failed.
This one has the same great functionality as before. I have never experienced anything malicious functionally and am glad to hear this implementation is clean.

it actually works on soundcloud!!!!!! and it just works all around, super good

I thought this extension was gone for ever! It's finally back?!?!?! Its so useful especially when the video's audio track is very soft and slow!!