Red-book CDs (the kind you play on a home/car stereo/discman/etc...) are always 16-bit 44.1 khz. What this means is that your digital audio contains 44,100 samples a second, with each sample containing 16-bits of information.
BUT, there are many advantages to tracking/mixing 24-bit stuff, even if the final delivery is 16-bit CD audio (or even mp3s)
Here's an analogy - Say you take digital photos, manipulate them, and then eventually post them on a website. Well if you plan on doing any manipulation, you'd be better off with a higher quality image to begin with. The resulting transformations would be better on a larger file, than on a smaller file. The same holds true with audio. When you are mixing, you are digitally altering the file (or audio stream if you're not doing anything destructive to the original waves). This includes panning, faders, effects, and of course summing everything to stereo. These manipulations are much better if done at 24-bit than at 16-bit.
Now when you're ready to get the final mixdown to stereo, you have to get the 24-bit file to 16-bits, so obviously you have get rid of information on each sample. You can either simply truncate the file (just drop the higher bits) or dither, which I won't get into here, but it involves both dropping the higher bits (which you have to do anyway) but also manipulate the remaining 16-bits a certain way. I believe you're much better off if you dither rather than just truncate.
One other advantage to 24 bits is that it allows you to record your parts at a lower level and still have a fair amount of detail captured. This allows you track lower and not worry as much about clipping if you get to close to 0. With 16-bit you have to get alot closer to 0 to have the same amount of detail. With 24-bit, I routinely track between -6 and -10 and i have no problems with the quality of the tracks.
Hope that helps!
Thom IV said:
Not sure if it's dithering that ultimately converts 24 bit to 16 bit when burning to CD...there are some things I'm still trying to get a handle on...
You'll have to do more research and ask more knowledgeable folks than I to understand the "why and wherefore" of this...
Several people on several bbs have told me that CDs support 16 bit only...(doesn't mean it's not true). I have several books that discuss this to some degree, although nothing specific to your particular question.
I'm still trying to find some corrobatory, "official" web resources that support this...if I find any, I'll try to look up this thread and let you know.
Tom