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The Occasion
On March 18, 1999, a dedicated group of
audiophiles, acting as life support systems for
some of the best ears in the industry, met in San
Clemente, California to do some critical listening.
We gathered at the home of Joe Harley, a prominent
music producer, for our first comparison tests of
the Sony-Philips Direct Stream Digital recording
process, in a controlled environment. That means
controlled by us, not Sony; using a high-end
playback system in a real home, as opposed to a
collection of unfamiliar commercial audio
components in a hotel room with unknown acoustic
properties; and comparing real production Super
Audio Compact Discs to real production CDs made
from the same master tapes.
The Listeners
Those present included our host Joe Harley, who is
well known among audiophiles as the producer of
some of the best-sounding blues and jazz recordings
available today; Richard Vandersteen and his wife
Enika, of Vandersteen Audio, the makers of the
time- and phase-accurate loudspeakers used for this
test; Bill Low, the founder and president of
AudioQuest, who funded the recordings that we would
use for the comparisons; Steve McCormack, founder
of McCormack Audio (now a division of
Conrad-Johnson), manufacturers of high-quality
solid-state electronic components; and me, Richard
Hardesty, audio equipment review editor of
Widescreen Review magazine.
The Methodology
Joe Harley records live to two-track analog tape,
using multiple microphones. Everyone present at
this test was familiar with the outstanding,
lifelike sound of his recordings and we have had
heard direct comparisons between the original
master tapes and the compact discs and vinyl
records made from these masters.
Two future AudioQuest Music releases, Soul
Survivor, The Best of Mighty Sam McClain; and Blues
Quest, a compilation of blues cuts from a variety
of artists, were used for the comparisons. These
recordings were remastered from the original analog
tapes by Sony, using the Direct Stream Digital
process, and transferred to production Super Audio
Compact Discs, for our comparison to regular
44kHz/16-bit compact discs, mastered from the same
source material.
The Direct Stream Digital recording process
represents a paradigm shift from the linear pulse
code modulation (PCM) system used to digitally
encode music for storage on conventional compact
discs. LPCM for CDs takes a 16-bit digital sample
of the analog waveform, 44,100 times per second.
DSD is a pulse density modulation system that uses
1-bit samples, taken at a rate of 2.8mHz (that's
two million, eight hundred thousand times a
second). There is a fairly complete description of
the DSD technology and the Super Audio Compact Disc
in my article "Hi Fi '98 Show News" in Issue #29 of
Widescreen Review.
The recordings that we used for this comparison
will be released in the future as Super Audio
Compact Discs in the DSD format. They will also be
available in the near future as "red book" standard
CDs made by downconverting the DSD master to
44kHz/16-bit LPCM. Downconversion is accomplished
by a Sony system called Super Bit Mapping
Direct™, which delivers improved sound quality
from regular CDs played on regular CD players.
Mobile Fidelity Sound Labs is currently producing
all their CD discs this way, and AudioQuest will
probably do the same on their future releases.
We listened to separate SACD and regular production
CD discs, playing first one and then the other.
Each listener had their own methods of evaluation,
and we each got the chance to go back and forth
between the two formats, trading off sitting in the
sweet spot, until we were satisfied with the
comparison.
The Hardware
Sony provided a prototype Super Audio CD player
that was also capable of playing regular CDs. The
two channel analog signal from this device was fed
via AudioQuest Diamond x 3 single-ended
interconnects through a Sonic Frontiers SFL-2
vacuum tube, line stage preamplifier. The preamp
output was routed through AudioQuest Diamond x 3
balanced interconnect cables to the Audio Research
V140 tube, mono amplifiers and then through
AudioQuest Dragon speaker cables to the Vandersteen
Model Five loudspeakers. The Model Fives are a
time- and phase-accurate, minimum-diffraction
design, that include an internally amplified
subwoofer system with a patented driver and room
contour controls for bass frequencies in each
speaker. This playback system is Joe Harley's home
hi fi, and the sound was simply stunning, even when
using regular compact discs as a source.
Stereophile's Gordon Holt has described the sound
of CDs as slightly "bottled up" when compared to
analog, I love that description, 'cause that's
exactly how I would describe what I hear. While CDs
made from Joe's recordings deliver outstanding
sound that would be hard to fault without direct
comparison to the original master tapes, there is a
limit to what can be achieved on a "red book"
standard compact disc. The Super Audio discs, on
the other hand, let the genie out of the bottle.
The high resolution of the playback system allowed
the differences between the two formats to be
easily heard. Describing the distinctions concisely
in words will be a little more difficult, but I'll
try, after a brief description of the difference
between the technologies.
The Technologies
The compact disc format is bandwidth limited due to
the 44.1k sample rate, necessitating steep filter
slopes below the Nyquist frequency (half the sample
rate) to prevent aliasing. This plays havoc with
phase relationships in the mid to high frequencies,
reducing the sense of "air" and depreciating
spatial localization and depth illusion (imaging),
when compared to high quality analog. Phase shifts
and filter ringing due to these steep-slope
filters, sometimes result in a slightly hard or
"edgy" sound from CDs.
16-bit digital samples are insufficient to capture
the low-level detail that is clearly audible on the
analog originals, and can still be easily heard on
vinyl records. Micro-detail is almost completely
missing on the CD, and this reduction of low-level
information further degrades imaging, and CDs fail
to capture the natural decay of musical notes and
other sounds, making them sound slightly
"sterile."
The Direct Stream Digital format has bandwidth out
to 100kHz or so, allowing the use of filters with
more conservative slopes. No conventional audio
DACs are required to reassemble the signal. The
accurate replication of square waves at relatively
high frequencies (10kHz)&emdash;which can not be
reproduced with any resemblance to the input signal
by CD&emdash;becomes possible with DSD. Pulse
density modulation with very high sample rates is
capable of high resolution at very low signal
levels. Signal to noise ratios exceed 120dB which
is better than some so-called 24-bit DACs can
claim, and remember, only 16-bit resolution is
supported by the CD standard, even if mastering is
done at higher precision. DSD is theoretically a
giant step forward for fidelity. But theory and
real-world results don't always correlate like you
would expect them to.
We were all excited to hear real, production Super
Audio Compact Discs to see if the theoretic
advantages of the Direct Stream Digital recording
technology actually result in better audible sound
quality from a home system.
The Results
Did the DSD recordings sound better than the
regular CDs? Is a frog waterproof?
When I sat down to listen to the standard CDs, I
was immediately impressed with the sound of Joe's
audio system. These were recordings of artists with
whom I am very familiar, done in a style that I
know well, played back on some of my favorite
equipment. The sound could only be described as
excellent. Yet when we switched to the SACDs, it
was like pulling back a gauze curtain that had been
placed between the performer and the listener.
There was no noticeable change in tonal balance,
but the increase in the amount of audible
"information" was startling.
The sound of a slide on a guitar string could
almost convince you that the musician was there
with us, in the room. Each note faded to an
inaudible level gradually, with the natural decay
that you would hear in a live performance. Voices
sounded like humans singing, not like a hi fi
playing, with a lot more harmonic texture. Images
that I would have described as pretty convincing
from the CD were strikingly more focused and three
dimensional from the SACD, even off-axis! Artists
had a more specific place in space and there was a
palpable sense of air around them, making the
overall presentation more natural and lifelike.
Recordings of my instrument, the piano, were
harmonically rich, with a fuller, and more
realistic-sound, that outperformed the CD by a
substantial margin. The piano action could be
clearly heard from the SACD, and the natural decay
of each note was accurately rendered.
Everyone present agreed that the improvement in
sound quality delivered by the SACD was quite
dramatic. Though our tastes differ, music is
important to each of us. Music is an emotional
communication, and the "goose bump" factor is the
best way to evaluate the successful delivery of
this message. The SACD beats the standard CD by a
mile in this regard. I think that this is a giant
leap for mankind. At least for the discerning music
lovers among us.
The Future
I've been listening to 96kHz/24-bit LPCM recordings
on DVD discs at home for some time now, and they
are very impressive too. We plan to do a comparison
between 96/24 LPCM and SACD/DSD soon, and I'll
report on the results.
If there is a format war, we can't lose. Each of
these new technologies can represent the biggest
single leap in fidelity that I have experienced in
my decades in the industry. At this stage of the
game, I'm rooting for Direct Stream Digital as the
technology with the potential for the highest
fidelity, and I think that the SACD has the best
chance of achieving commercial success, because of
the backward compatibility issue. Super Audio
Compact Discs will play in all the disc machines
that you have right now, due to the "red book" CD
layer. Laser disc players will play them as if they
were CDs and DVD players will too. They will play
in your car and in portable machines, with at least
the same quality that you get now from regular CDs.
You can start to collect them even before upgrading
to a new SACD player and retailers can sell them
from a single inventory.
I'm excited about the future. Fidelity is going to
get a lot higher, real soon.
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