User Guide and
Technical Information
page 13
SOUND DEVICES, LLC
Naming USBPre Hardware
Audio Playback
A user-defined name can be associated with each
USBPre. This name appears in audio application
software - typically in the device selection menu.
From the factory the default name is “USBPre
Microphone Interface”. This name is written to
non-volatile memory inside the USBPre, and will
appear whenever the USBPre is connected.
To change the default name:
1. Connect the USBPre to the computer.
2. Open the Control Panel application.
3. Highlight the name in the Device Selection
area.
4. Enter a new name and hit “enter”. Follow the
on-screen instruction.
5. Disconnect the USBPre, then reconnect. The
name will be written to the USBPre firmware.
Renaming the USBPre
When connected to a computer the USBPre
becomes the preferred audio hardware. To test
whether the USBPre is properly playing audio, per-
form the following test:
1. Connect the USBPre to the computer.
2. Select the USBPre as the preferred device
(see Selecting the USBPre in Windows)
3. Connect headphones or powered loudspeak-
ers to the output of the USBPre.
4. Double-click on the file Play Me.wav on the
Sound Devices installation CD. This is a 16-bit
/ 44.1 kHz wave file.
5. Listen to verify that audio is playing through
the USBPre.
The USBPre can be used to transfer digital audio
into and out of a computer via coaxial S/PDIF.
Input
The USBPre can accept S/PDIF input sources
at 16, 20, and 24-bit and with sample rates of
32, 44.1, and 48 kHz. With Windows 98SE and
Windows 2000 a full 24-bit signal will be trans-
ferred. In Windows Me signals with bit depths high-
er than 16-bit will be truncated to 16-bit. The input
selection LED flashes without S/PDIF connection
and turns solid when a valid S/PDIF source is con-
nected.
Output
In Windows 98SE and 2000 the output of the
USBPre is limited to 16-bit with wave audio (using
the ASIO drivers enables a maximum output of
20 bits via S/PDIF). A 20 or 24-bit signal sent to
the USBPre will output 16-bit data via the analog
output.
To improve the transfer of digital audio, the
USBPre Control Panel has an S/PDIF output sync
selection. With no sync selected devices con-
nected to the USBPre’s S/PDIF output may take
several seconds to “lock-up” to the S/PDIF signal.
During lock-up, objectionable audible artifacts are
present. When no audio is present the S/PDIF out-
put is inactive. When an output sync sample rate
is selected in the Control Panel the S/PDIF output
port is always active, sending 0’s at the selected
sample rate when no audio is present. This greatly
improves the performance of transfers from the
S/PDIF output, since a lengthy pre-roll is not
required to lock-up the data.
NOTE: Selecting an output sync sample rate in the con-
trol panel may have a negative on audio performance
since all audio, regardless of its native sample rate, will
output at the selected sync rate. Sample rate conver-
sion will occur in Windows when the computer receives
an audio signal at a frequency that is different from the
selected sync sample rate. Again, make certain that the
selected output sync sample rate matches the sample
rate of the files being played, otherwise sample rate con-
version will occur.
S/PDIF Input and Output
