Owner`s manual

158 July/August 2013 the absolute sound
problem.” His review generated quite a bit of controversy, with
some audiophiles agreeing that the DAC1 was utterly transparent,
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pace, and ambience retrieval.
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haven’t spent much time listening to the DAC1 so I wouldn’t
venture an opinion on its ultimate sonic quality. But after more
than three months with the Benchmark DAC2 HGC I can’t help
but think that it will convert Benchmark naysayers into fans.
Going From DAC1 to DAC2
How does the Benchmark DAC2 HGC differ from its
predecessor? It looks very much the same to the casual eye
since it has a similar physical footprint and front-panel layout.
According to the DAC2 HGC’s owner’s manual, “New features
have been added to extend the versatility of the product, and
improve the listening experience. These features include: native
DSD conversion, asynchronous USB 2.0, asynchronous USB
1.1, home-theater bypass, digital pass-through, polarity control,
word-length display, sample-rate display, a bi-directional 12V
trigger, and additional I/O options.” Additional “performance
improvements” include using four balanced 32-bit D-to-A
converters that are summed to make each balanced output
channel. According to Benchmark this reduces noise by 6dB.
Overall the DAC2 is 10dB quieter than the DAC1. The DAC2
also includes 3.5dB of digital-processing headroom above
0dBFS, which reportedly eliminates the clipping that can be
caused by inter-sample overloads.
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power supplies with each subsystem using its own dedicated
low-noise regulation. The UltraLock2 digital clock replaces
the older UltraLock clock that was used in the DAC1 for jitter
attenuation. Like most current-generation DACs, the DAC2 uses
an asynchronous interface, which Benchmark, with a knack for
verbal invention, calls its “multi-mode asynchronous USB.”
The HGC moniker stands for “hybrid gain control” which is
a “dual domain” attenuation system that combines digital with
analog gain controls for an optimal result. By using a 32-bit
digital system along with a servo-driven analog potentiometer,
Benchmark claims that the HGC design “outperforms traditional
analog or digital volume controls, including the two-stage DAC1
HDR system.”
The expanded input options for the DAC2 HGC include two
pairs of unbalanced analog stereo inputs, two optical digital
inputs, two coaxial S/PDIF inputs, and one USB 2.0 input.
Output options comprise two pairs of unbalanced RCA stereo
outputs, one balanced XLR stereo output, and two ¼" stereo
headphone outputs on the front panel. All the outputs are
attenuated by the front-panel rotary volume control. The DAC 2
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to be a digital output, so that any digital source that comes into
the DAC2 HGC can be rerouted to any additional external
digital devices you have on hand, such as another DAC or digital
recorder.
Most of the front panel’s operating adjustments are duplicated
on the DAC2’s dedicated remote control. Looking very much like
the remote that Bel Canto used several years ago for its PRE-3
analog preamp (the Bel Canto was plastic; the Benchmark die-
cast aluminum), the DAC2 HGC remote handles volume, input
switching, LCD levels, and on/off functions. The only control
not duplicated on the remote is polarity reversal. To invert the
polarity you must push a small button on the DAC2 HGC’s front
panel or the remote control’s On button.
Like its predecessor the DAC1, the DAC2 has a pair of ¼"
stereo headphone outputs on its front faceplate. Benchmark calls
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with a “near 0-ohm” output impedance for optimum damping
with a wide variety of headphones.
Setup and Day-to-Day Operation
Setting up the DAC2 HGC was straightforward with few surprises.
For my desktop system I connected the balanced XLR outputs
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to my subwoofer, while the other RCA single-ended output was
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Inside the DAC2 HGC Benchmark included a pair of jumper-
enabled passive attenuators for the balanced XLR outputs. This
switch lets users choose either 0dB, 10dB, or 20dB of attenuation.
The purpose of the attenuators is to match the DAC2 HGC’s
output levels to your amp and speaker sensitivity. Benchmark
recommends that for optimal performance the volume control
should be set above 11 o’clock. The DAC2 came with the
jumpers set for -10dB, which I reset for -20dB. For desktop use I
found that -10dB was far more gain than I needed with the amps
and speakers I had on hand.
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operate one of two ways—either all the other outputs are
muted when a headphone is plugged into the front panel or they
remain active. Both schemes have their adherents and detractors.
Benchmark came up with a clever compromise. If you use the
left-hand jack the DAC2 attenuates its other outputs, but if you
use the right-hand jack all outputs remain active. Benchmark’s
solution is hard to fault.
Since the DAC2 HGC uses a servomotor to control its remote
volume adjustments, volume changes aren’t as instantaneous as
they are with an all-electronic volume control. Once you release
the volume control button on the remote the DAC2 volume
continues to travel for a fraction of a second. Also the volume
knob has no detents (or numerical equivalents on an LED
readout), so recreating exact volume levels can only be done “by
eye” using the small red dot on the volume knob and the dot
markings around the outside circumference of the knob. I found
turning the control manually rather than relying on the remote
worked best for achieving critically matched volume levels.
The DAC2 Sound
Although the latest generation of DAC chips and circuits claims to
have achieved that elusive goal of bit-perfect sound reproduction
(still debatable), different approaches to digital signal processing
and analog circuitry create more than enough variations in sound
quality to give most DACs their own unique sonic personalities.
Benchmark says that the DAC1 and DAC2 use nearly identical
analog circuit. The difference is the DAC2’s ESS Sabre conversion
and DSP headroom. The company says that in the DAC1 the
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