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DVD-A
and SACD. Date Posted 27/08/2001.
The CD has been around
for nearly twenty years, and was designed to be the final format, which
would offer the best quality sound possible. However, many people still
complain that vinyl sounds better. Because of these criticisms of CD,
it was not surprising that various hi-fi manufacturers have developed
new formats, to address these concerns. Another major motivation has been
the fact that Sony and Philips (who invented the CD) are going to lose
out on commission from CD patents in a few years.
Sony have Super Audio
CD. It uses a new system to record audio DSM with a frequency of over
100 kHz - 2.82 MHz. In the Panasonic corner there is DVD Audio which works
at 24 bit 96 kHz recording in the traditional PCM format, which virtually
all digitally recorded audio uses. Both offer 5 channel audio, as opposed
to stereo (although not every disc will offer a 5 channel mix). At first
though only SACD stereo CDs were released, however, now 5 channel SACDs
are appearing on the market. It must be noted though that DVD-V also offers
multichannel sound, usually encoded in a compressed format like Dolby
Digital or DTS, which being compressed won't sound as good as DVD-A, SACD
or CD for that matter. DVD-A, SACD and CD are uncompressed formats.
Let's first look at
the case for DVD-A. Our ears have an approximate range of 20 Hz to 20
kHz. Although we can't hear sounds of higher frequency, sounds recorded
at 96 kHz will be a more accurate representation of the sound than those
recorded at 20 kHz. Also being a 24 bit format, the you will have a better
range of dynamics, something better for classical music rather than pop
music (which is often about the same volume throughout a track). Sound
is a wave, and when it is recorded using PCM it is approximated using
a process called quantization, so if you were to zoom in it would like
a jagged representation of the actual wave, the higher the bit rate and
frequency the smoother the wave would look and consequently the more accurate
it would be to the original recording. Most sound waves are smooth (except
some synthesised sounds) and so this process of quantization is very important,
and is performed by an analogue to digital convertor. Basically DVD-A
is like CD but offers a more accurate way of quantization. The idea of
converting data to a digital format (rather than leaving it in an analogue
format, like cassette or vinyl), is that it will sound virtually identical
when played back and won't degrade as much over time. Also copies are
100% identical. SACD uses a new technology called DSD, which has a different
form of of converting audio into a digital form, which does not need so
many filters as DVD-A or CD to be converted into digital. The 2.82 MHz
is incredibly high too.
On the face of it
both formats are far better than CDs, which store audio at what must seem
a pedestrian 16 bit 44 kHz. Both DVD-A discs and Super Audio CD discs
look like CDs. Consequently both DVD-A and Super Audio CD players can
also play CDs (some play DVD-Videos too). Unfortunately, given that each
manufacturer is pushing their format, they are in no will to compromise,
which probably explains the lack of "Super machine" which can
play both DVD-A and Super Audio CD. In addition, many Super Audio CD's
have an additional layer (but not all!), so they can work on ordinary
CD players. Obviously, though it will not sound as good as if played on
a Super Audio CD. DVD-A does not work in any CD player. Only certain more
expensive DVD-V players can play DVD-A, so before buying a DVD-V make
sure you check it also works with DVD-A.
I have not heard either
DVD-A or Super Audio CD so I cannot say which is better. Audiophiles are
still largely undecided on the question of DVD-A, Super Audio CD, CD or
vinyl. However, there is now a movement towards to SACD, which some say
sounds better than DVD-A because of DVD-A's copy protection system and
the new DSD system. This DVD-A system uses an analogue watermark, which
is supposed to be unaudible, but some say degrades the sound. At the end
of the day the only way to find out would be to listen to an identical
recording of DVD-A and SACD side by side.
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