Overview - Benchmark ADC1 USB Instruction Manual

Overview

The ADC1 USB is a reference-quality, 2-
channel, 192-kHz, 24-bit, analog-to-digital
converter featuring Benchmark's Advanced
USB Audio™ technology, phase-accurate
UltraLock™ clock system with multi-function
clock input and word clock output, and
Benchmark's 9-segment dual-range digital
LED metering. The ADC1 USB is designed for
maximum transparency and is well suited for
the most demanding applications in studios
and mastering facilities. A rugged and
compact half-wide 1 RU enclosure also makes
the ADC1 USB an excellent choice for location
recording, broadcast facilities, and mobile
rigs. The internal power supply supports all
international voltages and has generous
margins for over and under voltage
conditions.
The ADC1 USB achieves outstanding
performance over a wide range of input
levels. Each channel has a 41-detent variable
gain control, a 10-turn gain calibration
trimmer, and a 3-position first-stage gain
switch (0, 10, and 20 dB). The gain
calibration controls may be used to calibrate
the ADC1 USB to precise studio reference
levels. The variable gain controls may be used
to optimize the gain-staging between a
microphone preamplifier and the ADC1 USB.
Both the pot and the trimmer have a 24 dB
adjustment range. In combination with the
first-stage gain switch, these controls provide
exceptional SNR and THD+N performance
over a 44 dB adjustment range. Each channel
has a two-position toggle switch that selects
between the variable and calibrated gain
control.
The ADC1 USB has a total of 5 stereo digital
outputs (1 XLR, 2 coaxial, 1 optical and 1
USB). The digital outputs can operate
simultaneously at up to three independent
sample rates. The auxiliary coaxial output
can be configured for 16-bit TPDF dithered
output. This unique flexibility enables
simultaneous recording to a CDR, a high-
resolution digital recorder, and a high
resolution DAW. For example the CDR may
operate at 44.1/16, while the DAW operates
ADC1 USB Instruction Manual – Rev C
at 88.2/24, while the digital recorder operates
at 192/24. The optical output supports AES
or ADAT formats at resolutions up to 192/24.
In ADAT mode, high sample rates are
supported using SMUX2 and SMUX4. Backup
and/or demo recordings can be created with
ease while high-resolution outputs are fed to
primary recording devices.
The ADC1 USB has a BNC Word Clock output
that follows the sample rate of the Main
Outputs. Word Clock output is active in all
modes of operation.
A multi-format clock-input automatically
recognizes AES/EBU, SPDIF, Word Clock, or
Super Clock signals. This clock input is used
to synchronize the Main Outputs. If desired,
the Main Outputs may be driven from internal
sources. The ADC1 USB will automatically
revert to an internal clock source when the
external clock is lost.
The ADC1 USB has two clock modes: External
(Ext) and Internal. Both modes support 44.1,
48, 88.2, 96, 176.4 and 192 kHz.
The Ext mode allows the ADC1 USB to lock to
an external clock reference. In Ext mode, the
ADC1 USB will follow changes in sample rate,
and/or changes in the type of reference signal
(AES, SPDIF, word clock, or super clock).
When a clock reference is not available, the
internal mode must be used, and a sample-
rate must be selected (44.1, 48, 88.2, 96,
176.4, or 192 kHz). When the Internal mode
is active, the ADC1 USB is acting as clock
master, operating at the selected sample
rate, and any signal at the clock reference
input will be ignored. If internal mode is used,
all devices connected to the ADC1 USB digital
outputs will need to be configured to lock to
the ADC1 USB. The clock output on the back
of the ADC1 USB can be used if the connected
device(s) require word clock.
The Benchmark UltraLock™ system is 100%
jitter immune. The A/D conversion clock is
totally isolated from the AES/EBU, SPDIF,
ADAT, WC, and super clock interfaces. This
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