Ok thanks. I'm confused why audio software having "software volume control" would be a bad thing. Yeah, I notice on my Mac the VLC volume (the "mouse wheel on video" volume) goes up to 200%! Never gave that much of a thought, except maybe everyone likes going to 11.

I assumed from the "not bit-perfect audio" that VLC somehow misses bits or something, as in, doesn't play all the music information, but from your comment it just sounds something to do with volume. I also don't understand a word of your second paragraph, but I won't worry about that—they sound like dark, arcane realms of knowledge safer to avoid.

When you use software volume control, you're not changing the volume of the speakers - you're changing the volume of the recording. If your speakers have any background hiss - and they do - then making the recording quieter makes that hiss easier to hear. What's more, even the recording itself actually inherently has a kind of "hiss" because, in any recording medium, there is a quietest possible sound.

You can hear it for yourself - turn the volume in VLC very low down, and your speakers all the way up to compensate, and listen to a record - it'll sound bad. The louder your speakers, the lower you'll be able to crank VLC, and the worse the whole thing will sound.

Making the recording louder is - theoretically - fine; it shouldn't make it sound any worse. But if the recording is well-mixed, there's no headroom to make it louder and it will distort - this is because the engineers make the recording as loud as possible to avoid exactly the above issue.

Thank you for explaining! (Also I'd love to read something 50x longer on the subject.)

If you alter the volume, you alter the bits (which means not bitperfect playback). It reduces the available bits.