Please don't claim "The best" whilst experimental.

Unable to boost audio where recordings were quiet, for example:

https://www.youtube.com/watch?v=_mEIv9wOkro

Compare with up-to-eleven:

https://addons.mozilla.org/addon/up-to-eleven/

Good interface and options. Sometimes the options get a little too technical.

However, the main reason for 2 stars is that it didn't work on Firefox 68.0.1 (64-bit), on music.amazon.com I haven't tested in other sites.