English - Weiss Engineering
by Alan Silverman
Weiss Engineering
ADG2 Analog-to-
Digital Converter
Daniel Weiss doesn’t disappoint with this
high-powered A/D converter
Weiss Engineering's latest edition of their
venerable ADC hews to the company’s purist
philosophy. The unit is quite nearly a digital
straight wire with gain. The converter
supports single and dual-wire out-
puts at sample rates up to 192 kHz.
Included are a pair of mic pre-
amps and a digital com-
pressor/ limiter derived
trom the company’s high-
ly regarded DS1 dynamics
processor, enabling the
Devices AD797 low-noise op amps, in a mini-
malist topology of only four op amps per
channel. Analog input level is passively con-
As in the Weiss DS1 compressor, release times
are adaptively varied from fast to slow
depending on a look-ahead analysis of the
input. These values are user adjustable on the
DS1, but are fixed at 30ms and 400ms, respec-
tively, in the ADC2. The same time constants
are applied in the limiter section. Attack time
is fixed at 0.315ms and there is overall system
delay of 1ms. Dynamics processing can be set
for linked-stereo or dual-mono operation.
Rounding out the feature set are sync-
source selection, low-cut filters and 48V
phantom power for the mic inputs,
analog/digital input selection, and POW-R
dither (with auto-black) tor 16-bit output. A
rear panel DIP switch sets the wire mode and
the sync termination mode. Simultaneous
AES and S/PDIF outputs are on the rear
panel and a FireWire port is planned.
ADC? to function as a
complete front end. AES digital
inputs, the dynamics processor
and POW-R dithering allow the
unit to be used for simple master-
ing applications as well.
The ADC?'s mic and line inputs share a
common amplifier, consisting of Analog
Studio, location, post production
Twochannel; 24-bit; up to 192 kHz
sample rate; digital limiter; POW-R
dithering; single/dual-wire
Weiss Engineering | =-41-44-586-
= WWW.Welss.ch
42 | Produdio Review | September 2006
trolled by a switched array of vacuum-zealed
gold contact relays permitting sensitivity set-
tings from —54 dB to 0 dB in 1 dB steps.
Channels can be controlled individually or
ganged for stereo operation. The minimal
number of gain stages and the passive level
control insure very low coloration of the input
signal before conversion. Input to the ADC?
stays fully balanced right up to the converter
chips, which are AKM 5.6 MHz delta-sigma
types. Two converters per channel are used in
a correlation technique that improves signal-
to-noise by 3 dB over a single-converter
design. A digital level control, ranging from
—100 dB to +18 dB, is available post-conver-
sion for further gain adjustments. Steps of 0.2
dB are implemented for fine control and
changes are click-free and zipperless.
A 40-bit floating point DSP module pro-
vides the engine for digital gain, precision
metering (with peak-hold) and the compres-
sor/limiter. The latter is a two-stage dynamics
processor consisting of a variable-threshold
2:1 compressor and a 1000:1 peak limiter with
a fixed threshold at 0 dB full-scale. To push the
limiter, set the digital gain control above 0 dB.
The ADC? was first sent out on a live
stereo session for a Manhattan-based audio-
phile record label. The unit was configured
for 192 kHz sampling in single-wire mode
and connected to a location Sequoia system
through a LynxStudio AES16 sound card. The
unit received the same feed as the label's own
reference converter. Back at my mastering
room, I put up the files for comparison. The
ADC? recording sounded excellent except for
a very subtle artifact in the highs. It came to
light that there was a low-level clock noise in
the ADC2 files. Oscillator tests revealed that
the clock noise only occurred when running
the ADC2 at 192 kHz in single-wire mode. At
all other speeds and modes the signal was
clean. I notitied Daniel Weiss and a short time
later he wrote that they verified the problem
and corrected it by shaving a few instructions
trom the unit's firmware. An EPROM was
sent that put the issue fully to rest.
The next set of tests involved comparisons
of the analog playback of an audiophile SACD
played through a Meitner professional DSD
DAC against various A/D-D/A converter
www. proaudioreview.com
WEISS Continued From Page 42
loops. A particularly useful SACD for this pur-
pose is Mark O'Connor's Hot Swing, featuring,
Jane Monheit and Wynton Marsalis, because
of its great vocal and instrumental sounds
tracked directly to DSD. Using a Meitner
Switchman II and a set of Y-cables, level-
matched comparisons could be made between
the source and up to three A/D-D/A chains.
Although it's not a single variable test, it real-
istically reflects workflow and gives a sense of
the colorations, or lack of same, characteristic
of each designer's work. One of the benefits of
writing tor PAR is the opportunity to put a
great variety of highend gear through its
paces. In the test were Weiss, Lavry Gold,
LavryBlue, Digital Audio Denmark AX24,
Mytek 8x192 and UA2192 — all excellent con-
verters. The Weiss chain sounded virtually
neutral with only a very slight op-amp signa-
ture. While some converter sets seemed to
subtly color the low /mid /hugh frequency bal-
ance of the source, the Weiss was quite faithful
to the input. Twould place it in the top two for
The ADC? was then sent to Avatar
Studios, here in Manhattan, for a series of
mix sessions with Grammy winning jazz
engineer Jim Anderson. The mixes later
came to Arf! for mastering. First up was a
new album of highly energetic modern jazz
by keyboard virtuoso D.D. Jackson. Mixing
was done on an SSL analog desk fed by Pro
Tools | HD and captured to a second system
by the ADC? at 24/96. The mixes sounded
like ideal analog in that there was no sense of
grain or harshness. This impression was
confirmed by the artist, himself an audio-
phile. The mixes took mastering EQ easily.
The second project was a Flamenco set
featuring a highly respected Spanish female
vocalist, Martirio, backed by piano, guitar,
trumpet, clarinet, bass, drums and percus-
sion. The apparent transparency of this set
was stunning. Jim later told me that Avatar's
house engineers were extremely impressed
with the converter and the studio's owners
eventually purchased an ADC2.
When the unit returned home, I set up an
informal mic preamp test with an artist
named Anja, a young woman possessed of
one of the most powerful and beautiful voic-
es I've heard in all my years of studio and
mastering work. A vintage M49 mic was split
to an Amek 9098, a Telefunken V72 restored
by Oliver Archut of TAB-Funkenwerk, and
the ADC?'s mic inputs. Anja sang loud
enough and high enough to make any mic
preamp quiver, not to mention the engineer.
The 9095 seemed to fold under the harmonic
intensity, the Y72 coasted with richness and
air, and the ADC? performed gracefully
under the pressure. The mic preamp in the
ADC? captured Anja's sound cleanly and
smoothly with little color added.
The ADC? is a sophisticated, audiophile-
quality converter with a musical soul.
Transparency and pristine sound are its hall-
marks. The onboard digital compressor/lim-
iter, unlinked independent channel operation,
mic preamps, digital inputs, and POW-R
dithering enhance versatility. Weiss
Engineering has an uncanny knack of building,
equipment that is both sonically neutral, yet
imparts a sense of refinement and elegance.
The ADC2 carries on in that tradition. As with
all things Weiss, it's hard to go wrong.
Alan Silverman has recently remastered The
Kinks" complete RCA and Arista catalogs for hybrid
SACD and was an album-of-the-year nominee at the
2004Latin Grammy Awards for mastering Lagrimas
Negras by Bebo Valdes and Diego El Cigala.
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