To those old enough, do you still remember the time when
music on CDs tends to sound better when they are recorded onto blank cassette
tapes?
By: Ringo Bones
Let’s face it early 1980s era CD players may have been built
like a tank – like that of cassette tape decks of the period. But when compared
to contemporary universal disc players that can play CDs DVDs or any 5-inch
diameter disc, the sound quality of early 1980s era CD players leaves much to
be desired. Even though in the 1990s we finally have names on the “audio
gremlins” that plague the Redbook Spec 16-Bit, 44.1-KHz digital audio – data
induced jitter for example – why is it that early 1980s era CDs sound quality
improves once it is transferred to cassette tapes, 8-Track, Elcaset or any
other analog magnetic recording media?
Even during the Golden Age of Stereo, audio engineers and
audiophiles already know that high-order very steep cutoff low pass and high
pass filters are deleterious to perceived sound quality. The reason why CDs –
and even low data rate MP3 audio files – tend to sound better when recorded on
analog magnetic media like cassettes, Elcaset, 8-Track, etc, is that analog
magnetic tapes doesn’t require a high order low pass filter as an
“anti-aliasing filter” to remove signals that doesn’t fit in to the Nyquist
Criterion of Redbook Spec CDs. Any signals too high in frequency to be recorded
in analog magnetic recording media just rolls off gently at a rate of 6 dB per
octave.
Why early CD players tend to sound worse than their more
contemporary counterparts is because anti-aliasing filters with very good
subjective sound quality were very difficult to design back in 1982. It was
Philips of Eindhoven, Netherlands that were the first to come up with an
oversampling digital filter – which is all about digital signal processing
algorithms – that resulted in a better sound quality than competing
anti-aliasing filters of the time, but digital signal processing was still at
its infancy in comparison to what we can do during the 1990s never mind today.
While Sony in Japan struggled on with impractical ninth-order analog brickwall
filters, Philips had no choice as they were unable to make reliable 16-bit
converters at the time of the CD’s 1982 CES debut.
By using oversampling and noise-shaping way back in 1983,
Philips could make their proprietary 14-bit converter for 16-bit 44.1-KHz
Redbook spec CD work with 16-bit resolution. Even though both Philips and
Sony’s CD players costs around 750 US dollars once they became available back
in 1983, a similarly priced machine in the mid 1990s can easily show it a clean
pair of heels sound quality wise. Today’s similarly priced machines are even
better. Would the hi-fi cassette tape decks role during the early days of CD is
a “widely available digital-to-analog-converter to make early CD sound better”?
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