Looking for "Sound" Advice: 16 bit vs 24 bit

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Joined: 12/10/2004

Hi,

I'm about to start transcribing vinyl LP's to CD and am getting conflicting advice on how to retain the best possible sound. :?

One 'audio specialist' reckons that the 16-bit conversion in an Apple Mac is all you need as that is what you finish up with in the CD format. On the other hand Tony Brooke's recommendation on this web site is for a separate 24-bit conversion using one of the devices listed there.

As I'm wanting to save the converted files to an iBook (dual USB) with no sound input port, I'm favouring the M-Audio Firewire Solo.

But now I'm wondering why not save the better 24 bit sound files to a hard drive and use that for play back. The spreadsheet calculator shows that you can have something like 40 hours of music on a 20 GB hard drive. Are audiophiles actually doing this for some of their favoured pieces?

Am I correct in assuming that a module like the Firewire Solo can also handle the D/A conversion for playback?

Thanks,

John

John Wolff
Hamilton, New Zealand

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Joined: 02/12/2009

It's a common misconception that "recording at 16 bit is good enough since the final medium is a 16 bit CD." This is wrong but it's understandable that people think so. That's like saying that your city's water distribution plant should use 1/2" pipes because that's what your toilet has. In digital audio, it's best to use the fattest pipe you can until as late a stage as possible.

Every stage of the process from source to destination (be it analog LP-->CD, or CD-->MP3, or 24bit master-->SACD) has a cumulative effect on the final product. In the analog world, it shows in the form of noise, decreased dynamic range, weak frequency response etc.

In the digital world, it's much less pronounced but degradation does occur. Each digital processing stage (volume change, EQ, compression etc) involves huge math functions performed on long numbers. The greater the bit depth (aka longer word length), the more precision the processing can use. Less bits means more rounding errors.

As an example of this effect, when you divide .7 by 2, you should get .35. But if you only have one decimal place to work with, you get either .3 or .4, (depending on if you round it up or down). On the other hand, if you have two decimal places to work with, you get the correct value of .35.

So it is with 16 bit audio (and it's 16 digits) vrs 24 bit audio (24 digits). 24 bit audio has more decimal places to work with, so the math is more accurate.

And of course, 24 bit audio itself (as opposed to the processing described above) is a more accurate representation of the source than 16 bit audio because of the greater detail of the extra 8 bits.

Some might still argue that 16 bits is good enough because the final CD is only 16 bits. They think that the intermediate steps have no effect on the end. I would question any "audio specialist" that thinks this way. If you believe that, try recording to cassette then transferring it to a 16 bit CD. Hmmm, does that sound the same as recording directly to a CD recorder? That answer would be no.

For more sources on this deep topic, try these links:
http://www.silentway.com/directory-audio-engineering-recording-studios-music-business-links

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As for your other questions, as long as your audio player app can play back 24 bit files (not all can), then go for it! Hard drives are so cheap and huge these days that it's worth it.

I for one do not compress my favorite music at all. Instead of MP3 I rip it to my drive as AIFF or WAV. But the metadata capabilities of other file formats is appealing. Check out more recent file formats like AAC, Apple Lossless and OGG too.

More on this:
http://www.silentway.com/node/1170
http://www.hydrogenaud.io/forums/

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Joined: 12/10/2004

Thanks Tony for your reply with the"Sound Advice." Your response has the info I was anticipating but could not find elswhere. It's just the same as we do in Photoshop -- take in 16 bits/channel from a Digicam or scanner then output at 8 bits/channel 'cos that's all you will ever see from a colour printer. But meantime you have kept maximal colour fidelity for the tweaking that's required to get the picture you want.

For me, however, there is still a huge nomenclature 'gap.' The Apogee white paper covers some of this but I'm still wondering what are the meanings of TRS and S/PDIF. It's terminology which is obviously second nature to you audio buffs but utterly geek-speak to me!!

Hopefully another pointer to an appropriate link will help me make the transition.

Cheers,

John

John Wolff
Hamilton, New Zealand

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Joined: 02/12/2009

Indeed, I am the pointer-master...

http://www.sweetwater.com/insync/redirect_letter.php?letter=A

and in turn
http://www.sweetwater.com/insync/trs/
http://www.sweetwater.com/insync/s-pdif/

many more there... it's as fun as reading the dictionary...

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