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August 2003
World
Premiere!
The Dodson DA-218
Ultimate
DAC?
Review
By Wayne Donnelly
Click here
to e-mail reviewer.
It
seems most appropriate that my first contribution to
the online resurrection of Ultimate Audio (one of my
previous reviewing gigs) concerns the Dodson DA-218 DAC.
Ralph Dodson is a gifted, experienced and quality-obsessed
digital engineer who for a decade or so has been relentlessly
pursuing the creation of the finest possible DAC. The
DA-218 is his most ambitious processor to date, and it
is an extremely impressive example of no-compromise design
and construction.
In creating the DA-218, Ralph
Dodson is throwing down the gauntlet to challenge
the industry's rush to sell SACD and/or DVD-A as
necessary developments to realize the full potential
of digitally based audio. He asserts that Red Book
(standard 44.1kHz) CDs properly reproduced -- i.e.,
through the DA-218-are sonically at least equivalent
to the newer formats. Dodson regards top-quality
analog sound as the real standard at which he has
aimed the DA-218, and he feels that he has at the
least come very close to matching that standard.
To give the reader a feel for the complexity
of Ralph Dodson's no-holds-barred conception
and accomplishment, the following section describes
key
innovations, parts choices and quality assurance methods applied in
the DA-218. In redacting these descriptions from Dodson's web site
white paper, I have tried to maintain a reasonably high-level viewpoint.
Nonetheless, the non-technically-oriented reader may find this section
heavy going. But relax-there's no quiz.
Technical
Features Of The Dodson DA-218
Cryogenic
Treatment
When dissimilar metals are joined,
crystal boundaries form. Soldering a resistor to a
PC board results in stress and crystal formation. Even
before that stage, in the course of manufacturing and
assembly thousands of solder joins and copper crystal
boundaries form in the conductive copper layers of
each PC board.
In the DA-218 processor, cryogenic treatment
significantly reduces crystals formed in the copper
strata of the
PC board during manufacturing
and assembly-related soldering. Ralph Dodson confirms that the benefits
of cryogenic treatment are measurable as well as audible.
State-of-the-Art Upsampling and Oversampling
All input digital signals -- 32, 44.1, 48 or 88.2 kHz--are
upsampled to 96kHz using a very high accuracy algorithm that yields
a signal-to-noise ratio of -117dB.
After the input signal is converted to a 96kHz sampling rate,
the data go to an oversampling digital filter which oversamples
up to a 768kHz
(8 x 96kHz ) sampling rate and 24-bit word length before going to the
D/A converters.
Input signal jitter is eliminated by first clocking
the input signal into a storage memory, then re-clocking
the stored
input signal out
of the memory using a master clock with an unprecedented +/-2 picoseconds
of phase jitter. After re-clocking, balanced differential drivers send
the low-to-no-jitter re-clocked signal to the 24-bit/96kHz DAC chips.
Advanced Power Supply Design
Separate power supplies for the digital and
analog sections store over 100,000µf of filter capacitance,
enough for a small power amplifier. Custom capacitors made
to Dodson Audio's specifications connect to 13 low-noise
DC regulators, including multi-stage regulation for the critical
analog stages. The resulting very low driving resistance
and output noise prevent contamination in the analog circuits.
Super-Wideband Analog Filters
The analog filters that
follow the DACs are Frequency-Dependent
Negative Resistor types with very flat
frequency response. Because no audio
signals pass through the active part
of the filter, there is minimum distortion
and phase shift. Those low values are
crucial to sonic purity. The audio
signal path is DC coupled from the
DACs to the output connectors. A DC
servo keeps the output DC voltage offset
level to a low 0.005V, preventing sound
degradation from DC offset biasing
of DC-coupled power amplifiers and
loudspeakers.
The analog filters' bandwidth after
D/A conversion can therefore be increased
because of the high 768khz-sampled
24-bit data going to the
DAC chips. The analog filters have a super-wide 100kHz bandwidth that
allows more pure music to reach the listener's ears. These new 100kHz-wide
analog filters have only +/-0.1 degrees of intrinsic phase shift, essential
to reproducing a properly sized soundscape, precise instrument location
and overall musical purity.
Balanced-Signal Four-Layer Printed Circuit Boards
The four-layer PCBs support balanced signals throughout
the processor. The balanced architecture reduces signal jitter and
radiated digital noise. The PCBs feature the finest dielectrics and
materials, which enable extremely low clock jitter. There is no sound-debasing
nickel-plating in the connectors. The PCB connectors are silver-plated
directly over a copper base metal and then gold-plated over the silver
for lasting protection.
The PCBs easily accommodate upgrades. Key ICs are
inserted into sockets, not soldered. Extra socket locations
on both
the digital and analog
sections ensure upgradeability to future formats and D-to-A conversion
processes.
Bybee Quantum Purifiers
Bybee Quantum Purifiers connected to the AC input lines
remove quantum (shot) noise from the incoming AC voltage. Removing
quantum-level noise before the AC line voltage energizes the digital
and analog power supplies reduces power supply output noise and the
processor's analog noise floor, yielding improved dynamics and resolution.
Non-Magnetic Shielding
Non-magnetic silver-copper shielding integrated
into the DA-218 chassis and cover protects the power supplies
and analog circuits from both RFI and EMI. Magnetic (steel)
shielding located near analog circuits would degrade the
sound. A Faraday shield surrounds the digital circuits to
protect the analog circuits from radiated high-frequency
digital noise.
Vibration Damping
Special nonmagnetic damping plates on the
chassis and cover damp any vibrations that could corrupt
the sensitive analog circuits. Five custom isolating feet
strategically positioned on the chassis bottom provide excellent
protection from external vibration.
Exhaustive Testing And Fine Tuning
The upsampling and oversampling
board, left and right DAC modules,
Bybee Quantum Purifiers, Faraday shielding,
and left and right analog filters are
all either hand-soldered or hand-adjusted
and matched. Exclusive test software
written for an Audio Precision Cascade
tester is used to measure, adjust and
verify the stringent processor test
requirements. The Audio Precision tester
is also used to test the processor's
assembled motherboard prior to cryogenic
processing. After cryogenic processing,
the board is again tested to measure
the cryogenically improved performance
before final mechanical assembly.
The assembled DA-218 is burned in for 48 hours.
After that, the Audio Precision Cascade and Dodson
test programs are used to adjust
and hand
match the left and right DAC chips. Left vs. right channel phase is
hand-adjusted to +/- 0.1 degrees. The test programs include multi-tone
tests that simultaneously generate 1/3-octave signals to stimulate
the processor's digital inputs. Simultaneous 1/3-octave multi-signal
testing provides a more accurate depiction of music for matching the
left and right DACs and hand-adjusting the phase of the analog filters.
This custom multi-tone testing software is much more accurate than
standard single-frequency test programs.
Ins
And Outs
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| The
appearance of the silver-toned faceplate is simple
and elegant. Vertical channels divide it into three
sections, with all control pushbuttons and LED indicators
located in the center section. There are four Input
Select buttons and one to invert electrical polarity
(phase, if you prefer), all with corresponding LEDs.
Three additional LEDs indicate DVD (this one is inactive,
intended for future upgrades), De-emphasis (indicates
that a pre-emphasized CD is being decoded), and LOCK
(confirms the transport/DAC interface). The STANDBY
button at the far right is in effect the POWER switch,
as there is no separate mains switch. In standby mode,
the outputs and digital circuits are turned off, while
analog circuits remain powered up to avoid "cold start" sonic
harshness. |
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| The
rear panel is equally simple: the IEC jack; one set
each of RCA and XLR analog output jacks; digital inputs
labeled COAX 1 (RCA), COAX 2 (BNC) and OPTICAL (Toslink).
The optional AES/EBU (XLR) input, when installed, is
controlled by the front-panel AUX button. It is worth
noting that rapping on the enclosure results in dull
thuds but no ringing-confirming the superior chassis
damping of the DA-218. |
Review
Conditions
When I contacted
Ralph Dodson to request a review sample, he interrogated
me to satisfy himself first that my system is of sufficient
quality to do justice to the DA-218, and more particularly
that I could match the DAC with a transport of suitable
quality. Ralph's transport is Sony's original flagship
SCD-1 SACD player, and he agreed that my Sony SCD-777ES-whose
transport and circuitry are identical to the SCD-1 except
for the absence of balanced analog outputs-would be fine.
Unfortunately the 777's transport
logic went "walkabout" soon after the DA-218 arrived,
so I sent it off to Sony for repair, and for several
weeks
transport duty passed to the much-modified Pioneer
DV-434 that normally resides in the smaller upstairs
system. Perhaps because the modifications to the Pioneer
include Bybee Quantum Purifiers on the DIGITAL OUT,
the sonic differences between the two setups were surprisingly
minor. The Sony did eventually return, and was reinstated
as both the transport for the DA-218 and a worthy test
of Ralph Dodson's assertion that the DA-218 sounds
better playing standard CDs than a high-quality SACD
player on an SACD of the same recording.
Listening
To The DA-218
The DA-218
sounded wonderful from the start. No need this time to
endure weeks of break-in time before hearing the DAC at
its best, because Ralph Dodson sent me his well seasoned
demo processor which already had 300+ hours of playing
time.
Moments into the first listening session, it was clear
that the DA-218 plays in an altogether different league
than the various digital playback
sources I am accustomed to-with perhaps one exception. (More on that
below.)
It should surprise no one that the DA-218 is
a stellar performer on every audiophile criterion. The wideband
frequency extension and seamless octave-to-octave balance are
to these ears beyond reproach. Loud transients demonstrate
explosive dynamic attacks and realistically sustained decays.
The same is true at the micro end of the dynamic scale. For
instance, on the splendid-sounding Reference Recordings CD
of Leonard Bernstein's Candide Overture and Suite, the
delicate cymbal strikes emerge more clearly and concretely
from the complex orchestral texture than I recall having previously
heard on CD, and their decay is now audible for nearly a second
longer. The reverberation decay of the final fortissimo chord
of the Overture is now likewise audibly of longer duration
as it subsides into the noise floor.
The DA-218 delivers definite, if subtle, benefits in spatial
resolution. The soundscape improvements have less to do
with size per se than
with distinctly more precise, dimensional and stable imaging. [NOTE:
These observations reflect my perceptions of soundscaping prior to
placing the Shakti Hallograph Soundfield Optimizers (reviewed
in this issue) into the system. The Hallographs produce dramatic
increases in every dimension of the soundscape.]
The previously mentioned Bernstein CD also contains
his "Four Meditations from Mass." The third Meditation
offers an ideal test of soundscape depth. It begins with the
soft, insistent tapping of a drum, and develops from there
with a closely mic'ed solo cello, joined first by a heart stopping
percussion smash and then by a body of strings, with each element
clearly at a different depth in the soundscape. The DA-218
distinguishes those layers more distinctly than I have ever
heard, and renders the complicated harmonics with exceptional
precision.
At the heart of the DA-218's sonic personality is its almost
spooky tonal purity. Whatever is spinning in the transport,
be it Alison Krauss
+ Union Station or Andrew Manze and the Academy of Ancient Music, the
music seems to emerge out of infinite "blackness" and spring to life
effortlessly. There is none of the subtle digital "edge"-the slight
bleaching of harmonics that heretofore has almost always seemed to
signal my subconscious that I am listening to a CD. This absolute purity
and silent background allow the DA-218 to resolve a stunning degree
of low-level detail-again beyond my previous experience-bringing freshness
to even the most familiar recordings. Among those details, it seems,
are subtle timing cues. For instance, listening to the Eroica Quartet
playing Robert Schumann's first string quartet, or Patricia Barber
jamming instrumentally with her combo, I am not consciously aware of
the hair-trigger interplay among the musicians, but hearing these and
other favorite discs, I find myself being drawn ever deeper into the
music.
Face-Off: CD, SACD, And Vinyl
With the long-awaited
return of my repaired Sony SACD player it was finally time
to test Ralph Dodson's claim that the sound of the DA-218
yields nothing to SACD and little or nothing to LP.
The reader should know that my SCD-777ES is so extensively
modified that Mama Sony herself might not know her
child. Dan Wright of Modwright
in Portland, Oregon has "thrown the kitchen sink" at it-multiple DACs,
clock upgrade, numerous parts replacements and more--topped off by
the addition of his custom-designed, independently powered tube output
stage, which completely replaces Sony's stock analog circuitry. Dan's
work has raised the performance of this machine above any SACD player
I know. I emphasize this point so the reader will not mistakenly assume
that my comments on this player are applicable to a stock SCD-777ES.
Far from it! [An article on this and other Dan Wright modifications
is in progress.]
The analog setup comprises a Basis 2800 vacuum turntable,
Graham 2.2 arm and Transfiguration Temper moving-coil cartridge,
playing through
the Thor TA-3000 Mk.II tubed phono preamplifier -- also more than worthy
competition for the DA-218.
This shootout, of course, demanded that the
music be available on all three formats. I focused the comparisons
on two very familiar titles from Patricia Barber: Café Blue and Nightclub.
The 180-gram LPs were compared to both the original Premonition
CDs and the Mobile Fidelity SACD/CD hybrid reissues.
Starting with the standard CDs, I was initially taken aback
by how close -- virtually identical -- were the sounds
of the DA-218 using
the Sony as transport and the Sony as a stand-alone player. A few of
my listening buddies and I, listening under double-blind conditions,
gave up trying to distinguish them. After about a week, the DA-218
began to show a very small -- but now fairly consistently discernible
-- degree of superiority, primarily in low-frequency extension and
impact. After pondering this phenomenon, my guess is that the silver
Bybee purifiers used to modify the Sony's DIGITAL OUT needed a few
days to break in.
That first set of comparisons was facilitated by the remote
control and precise level-matching features of the VTL 7.5
pre-amplifier (review
in progress). Comparing SACD on the Sony with CD through the DA-218
was not as easy. When the Sony is playing an SACD the DIGITAL OUT is
disabled. I could compare the digital formats only by playing first
one and then the other.
The results of those comparisons varied. On "Autumn Leaves," SACD seemed
to give Barber's smoky voice slightly more body and her piano an extra
touch of richness compared to CD. But on her soaring vocalism at the
end of "Too Rich for my Blood," the CD through the DA-218 sounded just
a little more free and open compared to a slightly denser, almost darkish
rendition from SACD. These somewhat inconclusive results continued
throughout the two recordings. Let me emphasize that every comparison
was extremely close, and the quality and degree of difference are hard
to describe.
One observation deserves commentary, however. The difficult-to-distinguish
comparisons described here were between the original single-layer CDs
and the SACD layers of the hybrids. The CD layers of the hybrids were
inferior to both the SACD layers and the single-layer CDs. I have heard
two theories about this. One is that the necessity of reading through
the SACD layer disrupts the laser just enough to cause some degradation
of the CD layer's sound. The other -- what we may call the conspiracy
theory -- holds that in order to promote SACD, the CD layers of hybrid
discs are deliberately being made to sound worse. I'm damned if I know;
does anyone out there have an explanation?
There remained the question of the DA-218 -- and SACD -- versus vinyl.
To make a long story a little bit shorter, on these recordings at least,
the analog playback almost invariably won out, but by surprisingly
slight margins. These sessions were the first in my experience to demonstrate
near parity between digital and analog. I think these were eminently
fair comparisons, given that the aggregate prices of the two front
ends were also very close.
What
Does It Mean?
I don't think
there are many SACD players out there that equal the playback
quality of my radically modified SCD-777ES. It is clear
to me that Ralph Dodson's claim of parity with SACD cannot
be dismissed-and I have no doubt that against most SACD
players the DA-218 might well sound superior.
What about vinyl? For years now, from the time I was
dragged reluctantly into the digital age, for any listening
session likely to include both
CDs and LPs my practice has been to play the CDs first and then go
on to LP. That has avoided the letdowns frequently experienced in going
from analog to digital. But these days I mix the two formats willy-nilly,
just letting the music take me along. I can't give any digital component
higher praise than that.
The DA-218 costs $7,995 -- serious money, especially when
one can get a pretty decent-sounding SACD player or DVD-A
capable player for a
few hundred bucks. But I am filled with admiration for the DA-218,
for several reasons. First, it is phenomenal sound quality and the
uncompromising execution of the design. In addition, the DA-218 already
has enough processing power and parts upgradeability to accommodate
high-bit-rate digital formats in the future. (Perhaps Ralph is waiting
to see whether SACD or DVD-A emerges victorious from the current format
war.) The DA-218 is so good that it really is like hearing your CDs
as if the CDs themselves had magically been improved.
This writer has voted with his wallet. The damned
thing is addictive, and I am really getting a kick out of the
sonic refurbishing of my CD collection. For the time being
at least, I'm hanging on to the Sony for superb SACD playback
and its excellence as a transport for the DA-218. If innovative
design, flawless execution and virtually unprecedented performance
turn you on as they do me, you should audition this wonderful
machine.
Specifications
Digital Inputs,
Standard:
Coax 1: S/PDIF RCA input
Coax 2: S/PDIF BNC input
Optical: EIAJ Plastic Fiber Optic TosLink
Fourth Digital Input, Optional:
AUX: AES/EBU XLR input
Analog Outputs:
Single-ended RCA
Balanced XLR
Output Level: 2.3 Volts RMS single-ended
Frequency Response: 10Hz to 100kHz
Total Harmonic Distortion + Noise: .0008%
Output Impedance:
75 Ohms single-ended
150 Ohms balanced
Channel Separation: >120dB @ 1kHz
Signal Inverting: Digital Domain
Sampling Frequencies: 32, 44.1, 48, 88.2, 96
kHz (automatically selected)
Modularity/Upgradeability:
The upsampler module, microprocessor, digital filter and analog ICs
are socketed to facilitate future format upgrades.
Power, International: 105/220 VAC, 50/60 Hz
Dimensions: 3 x 17 x 12 (HxWxD in inches)
Silver faceplate is standard.
Black faceplate is available by special order.
Weight: 18 lbs.
Warranty: 3 years, transferable
Price: $7,995
Company
Information
Dodson Audio,
Inc.
14340 Marianopolis Way
San Diego, CA 92129
Voice: (858)
484-8199
E-mail:info@dodsonaudio.com
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