Sound Devices USBPre 2 - Manual (Page 18)

USBPre 2 User Guide and Technical Information
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Line Inputs
The Line Inputs use balanced, quarter-inch connectors and accept +4 dBu analog signal (sometimes
referred to as “Professional” line level). Wiring is tip: signal (+), ring: signal (-), and sleeve: ground.
Aux Inputs
The Aux Inputs use unbalanced, RCA connectors and accept -10 dBu analog signal (sometimes
referred to as “Consumer” line level). This input is designed for signal from CD players, camcorders,
portable DVD players, and other similar devices.
Signal output from turntables without built-in phono preamplifi ers is too weak for the USBPre 2’s Aux
Inputs. A separate phono preamplifi er may be required depending on the design of the turntable.
Digital Inputs
Digital signal in the S/PDIF format can be input to either the coaxial RCA connector or the optical
TOSLINK connector. If signal is present at both the optical and coaxial input, the signal from the
optical input takes precedence.
Sample rates below 32 kHz are not supported on the digital connections. The optical connections do not
support the 192 kHz sampling rate.
Input 2 Loop Source
Input 2 has an additional source labeled LOOP. This input source does not correspond to any physi-
cal connections on the USBPre 2. When LOOP is selected, input 2’s source is derived from the left
channel of the computer audio signal (post digital-to-analog conversion). The input 2 Gain Control
affects signal The Output Gain Control does not affect the level of the signal going in to input 2.
The LOOP source is useful for test and measurement applications where a reference signal is re-
quired to be routed back to an input.
Outputs and Monitoring
Headphone Output
The USBPre 2 has a high current headphone amplifi er for monitoring analog input audio, computer
audio, or a mix of both. The Headphone Volume Control adjusts the level of the signal to the head-
phones. The Headphone Volume Control knob and the Output Gain Control knob can be swapped
with the back panel DIP Switches.
See DIP Switch Options .
Caution: The USBPre 2 is capable of driving headphones to dangerously high levels. Be aware of head-
phone level controls at all times.
Use the Monitor Mix Control on the front panel to adjust the mix between direct audio from the in-
puts (fully counter-clockwise) and output audio from the computer (fully clockwise). The signal for
input audio is derived from the inputs before analog-to-digital conversion.