From: Bluechip <csbluechip_at_gmail.com>
Date: Thu, 14 Sep 2006 04:43:56 +0100

WOW! What a fantastic read - thanks gvb

BC

At 01:22 14/09/2006, you wrote:
>LOL!
>
>I love the research dude!
>
>I always thought that 2 inch tape is still the best!
>
>rocker
>
>----- Original Message -----
>From: "Jerry Van Baren" <gerald.vanbaren_at_smiths-aerospace.com>
>To: "Rockbox" <rockbox_at_cool.haxx.se>
>Sent: Wednesday, September 13, 2006 7:46 AM
>Subject: Re: 16/24bit?
>
>
>David Pedersen wrote:
> > Sorry, this migh be a silly question:
> >
> > I have approx. 200 MiniDiscs, filled with recordings. I now want to
> > transfer them into my Archos. The miniDiscs are mainly recorded with
> > 24bit technology. My soundCard on the computer only supports 16bit. Ok,
> > I know, that it is no problem to record the 24bit discs with my 16bit
> > soundcard, as I already have done so, in several cases; and then turn
> > the whole thing into MP3. But my question is:
> > Would I have any benefit of getting a 24bit soundcard for the
> > computer? Does the MP3 technology care for 24bit? And will the RB/Archos
> > give me better sound with the 24bits?
> >
> > David
> > Archos JBR v1, RB2.5
>
> From an engineering point of view, 24 bits is entirely marketing hype
>for everything but professional audio equipment, typically with very
>high price tags (hundreds to thousands of dollars).
>
>Dynamic range (dB) = 20 * log10(2^n)
>
>Bits Signal range (dB)
>16 96
>17 102
>18 108
>19 114
>20 120
>21 126
>22 132
>23 138
>24 144
>
>In order to get 16 bits of useful resolution (i.e. 16 bits of signal) in
>your digital stream, your analog front end (e.g. opamps plus associated
>components such as resistors and capacitors) must have a combined noise
>floor of significantly better than 96 dB.
>
>You also need to look at the signal to noise quality of the A/D
>itself... the highest quality A/Ds typically have a S/N rating of around
>120-126 dB (21-21 bits). This means a very high quality A/D with a high
>quality front end and an extremely high quality PCB (power supplies and
>layout is incredibly important) gets you 20-21 bits of real signal plus
>3-4 bits of noise. We are talking close to heroic measures with
>proportional costs here.
>
>The above is _before_ compression is applied.
>
>So my answers to your questions are:
>
>Q: Would I have any benefit of getting a 24bit soundcard for the computer?
>A: No. Soundcards plugged into PCs don't have anywhere close to 24 bits
>of useful resolution, despite the marking hype. PCI board physical
>restrictions make proper board layout to achieve extremely high quality
>audio impossible or nearly so. I suspect many, perhaps most, PC sound
>cards struggle to achieve true 16 bits of signal to noise ratio. The
>inside of a PC is saturated with electrical noise!
>
>Q: Does the MP3 technology care for 24bit?
>A: More bits is always better, but you will be throwing away a lot of
>information in the lossy compression so the result is highly unlikely to
>be distinguishable between "24 bits" and (true) 16 bits.
>
>Q: And will the RB/Archos give me better sound with the 24bits?
>A: Definitely not. The Archos hardware is nowhere close to the very
>careful design that 16 requires and miles away from the heroic measures
>that 20 bits require. The Archos was designed to be small, inexpensive,
>and used in relatively high noise (not sound booth quality) environments.
>
>I suspect, based on discussion on this mail list and my own empirical
>listening experiences (but _not_ on actual measurements) that the Archos
>hardware is probably on the order of 14 bits of signal and 2 bits of
>noise. If you had a perfect 24 bit signal (say a computer generated
>synth sound), you still cannot get any better than the Archos output S/N
>(and that is ignoring the compression losses as well).
>
>Minidisk audio is compressed as well (ATRAC), meaning your "24 bits"
>isn't really.
> <http://en.wikipedia.org/wiki/Minidisk>
>
>Are you sorry you asked now? ;-)
>gvb
Received on 2006-09-14