DAC1 USB
Instruction Manual Revision D
Page 7
Jitter-Immune
UltraLock
™
The Benchmark
UltraLock
™ system is nearly
100% jitter-immune. The D/A conversion
clock is isolated from the input digital audio
clock in a topology that outperforms two-
stage PLL designs. In fact, no jitter-induced
artifacts can be detected using an Audio
Precision System 2 Cascade test set.
Measurement limits include detection of
artifacts as low as -140 dBFS, application of
jitter amplitudes as high as 12.75 unit
intervals (UI) and application of jitter over a
frequency range of 2 Hz to 200 kHz.
Any signal that can be decoded by the USB or
AES/EBU receivers will be reproduced without
the addition of any measurable jitter artifacts.
The AES/EBU receiver IC has been selected
for its ability to accurately recover data in the
presence of very high jitter levels.
HPA2
™ Headphone Amplifier
Two ¼” headphone jacks are driven by the
HPA2
™ - Benchmark’s signature high-
current, 0-Ohm headphone amplifier. The
HPA2™ is capable of delivering the full
performance of the
DAC1 USB
into the
difficult loading presented by headphones.
The
HPA2
™ maintains less than 0.0003%
THD+N under full load.
Mute Function
The left-hand headphone jack includes a
switch that mutes the XLR and RCA analog
outputs when a headphone plug is inserted.
This mute feature can be disabled with
internal jumpers.
Volume Control
The front-panel
Volume Control
sets the
output level of the headphone jacks. It can
also be used to control the output level of the
balanced XLR and unbalanced RCA analog
outputs. A rear-panel switch selects
Variable
or
Calibrated
output levels. In
Variable
mode the analog outputs are
controlled by the
Volume Control
.
Direct Interfacing to Power
Amplifiers
The
DAC1 USB
is designed to interface
directly to power amps and powered studio
monitors in order to provide the cleanest and
shortest path from the digital source to the
monitor output. This often results in a
substantial improvement in sound quality.
10, 20, and 30 dB pads are provided for
interfacing directly to monitors and amplifiers
that often have too much input sensitivity to
handle high-level (+29 dBu) signal levels.
High-Current Output Drivers
The
DAC1 USB
features new high-current
output drivers that are capable of driving
300-Ohm loads without an increase in
distortion. They are also well suited for
driving long cables or high-capacitance loads.
‘Audio-Always’ Design
Philosophy
The
DAC1 USB
is designed to perform
gracefully in the presence of errors and
interruptions at the digital audio inputs. A
soft mute circuit eliminates pops when a
digital signal is applied. Power management
circuitry controls the muting and resetting of
all digital circuits upon removal and
application of power. Audio is present at the
outputs only 60 ms after applying a digital
input signal and only 500 ms after applying
power to the unit.
The
DAC1 USB
is designed to avoid all
unnecessary mute scenarios. Muting is only
enabled upon loss of power, or when digital
transmission errors occur. The
DAC1 USB
does not mute when the input data is all
zeros. Consequently, no audio is lost when
an audio transient follows full silence.
Furthermore, the
DAC1 USB
signal-to-noise
specifications represent the true system
performance, not just the performance of an
output mute circuit.
The
DAC1 USB
will operate even when
sample rate status bits are set incorrectly.
