Dithering? Yes No? When? Mp3 or Wav I'm confused, (as usual)

[mazz]

When a digital audio signal reaches very soft levels, the bits can start cycling off and on randomly because there isn't much resolution in the low volume levels. Dither adds a very small and inaudible noise to the signal to basically help keep more of the bits "on" when the level gets very low. Some say that this can increase the clarity of the sound, etc. Dithering is not necessary unless converting from 24 to 16 bit files, where there would be fewer bits to represent those very low level signals, hence a little "help" is needed.

I don't know if it makes a difference for Pop or loud types of music but it certainly wouldn't hurt to do it. Honestly I don't know if someone with a home studio could hear the effects or not, but it's not destructive to the sound even if it may not add anything so why not?

[mojobone]

It's not really like the end of the tape being chopped off; what we're talking about is the length of a digital word, to X number of decimal places. Truncation means that when there aren't enough bits (say, when you're converting a WAV file from 24 bits to 16bits) to represent all the numerals in all the decimal places, the last few decimals are discarded; they're simply cut off. Truncation introduces an amount of uncertainty, little amounts of imprecision that could eventually add up to a rounding error or errors.

While I'm fairly certain that you and I are never gonna hear a rounding error, dithering allows us to keep the extra information in our 24-bit words when we reduce the wordlength to 16; it's as near a thing to a free lunch as you'll ever find in the realm of engineering. Certainly, there are mastering engineers in mastering rooms that can hear and evaluate different 'flavors' of dither, which uses noise shaping to correct for such rounding errors, and if you're forced to reduce bit depth that's when you should dither, (and you should dither only once) but if someone else will master your project, by all means let them handle the dithering, cuz they've got better ears, rooms, monitors and more flavors of dither, plus the experience to know which will best suit your project.

The larger issue is that if what you're hearing isn't up to snuff, it's highly unlikely that dither is the problem. If you can hear a problem, it's more likely that your levels are too hot, not hot enough or you're leaning too heavily on your MP3 conversion.