Lots of weirdness going on here: None of the audio players have the same track gain as one another OR the original. JMRC and Foobar have the same peak but different track gain (maybe this is a ReplayGain problem?) Audirvana has almost the same gain as the original but totally different peak HQPlayer is the most fucked. I'd be curious to see what an inversion and subtraction (difference) between each player output and the original would look like. Not sure if that is any more valid or useful than the ReplayGain output, but it would at least be another perspective on what is happening. Another interesting data point would be to compare the old Foobar WASAPI plugin with the built-in WASAPI that was introduced a few versions ago. I feel like the sound changed between implementations.