VLC especially does not do this - it uses software volume control (by default, I think you might be able to change this on some platforms). It also makes it hard to select exactly 100% volume, by allowing the volume control to go over 100% without any kind of detent. The odds that you're getting bit-perfect audio out of VLC is extremely poor.

Side note - bit-perfect is very important when you want to listen to surround-encoded files (AC3, DTS) on a surround system over SPDIF. SPDIF only has bandwidth for two uncompressed PCM channels, so the way it works is basically compressed audio data pretending to be a PCM stream. If anything messes with the stream - if you touch the software volume knob - your surround system will start outputting digital static at maximum volume.

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.

"with bit-perfect audio quality." - isn't that what VLC does?"

Let's assume your audio files all have one of two sample rates:

- 44.1 kHz

- 48 kHz

When you play one of these audio files in VLC, will it:

A) Force the DAC to operate at the same sample rate as the file, or

B) Check the frequency at which the DAC is already operating and (if necessary) resample the stream before sending it to the DAC?

If the latter, then you won't get bit-perfect audio quality.