Operation; Controls & Indicators; Computer Configuration; Apple Macintosh Computers - Berkeley Audio Design Alpha USB User Manual

OPERATION

Controls & Indicators
• Output Select: switch selects coaxial SPDIF or balanced AES type output
• Status LED: Green indicates USB Lock, Amber indicates Standby
The Alpha USB has one control and one bi-color indicator LED. The digital audio output is
available as either a 75 ohm SPDIF signal on a BNC connector or as a 110 ohm balanced
AES type signal on an XLR connector. A switch on the rear panel selects which output is
active. Only one output is active at a time in order to minimize jitter. Whenever possible, use
of the balanced AES signal output is recommended for best performance.
The indicator LED on the front panel is amber when AC line power is on but the USB
connection is not active. As soon as the USB connection to the computer is established and
the computer and the Alpha USB are talking to each other, the LED turns green.
In normal use, AC power to the Alpha USB should be applied first. Then the computer should
be powered up or the USB cable connected. Nothing catastrophic happens if the computer
side is powered up first, but since the Alpha USB audio master oscillators are not powered, the
USB driver in the computer may become confused. If this happens, unplug the USB cable and
then plug it back in.
The Alpha USB has no AC power switch and is designed to be left powered on. It draws only
3 watts of power and when the USB input is not active, the unit goes into a standby mode.
The Alpha USB is designed to work with Apple Macintosh and Windows PC computers and
also works with Linux based music servers. For Linux, the operating system must be ALSA
1.0.23 or above. It must also have the ability to select the output device.
The Alpha USB interface conforms to the new USB 2.0 High Speed audio interface standard
that supports sample rates up to 192 kHz/24-bit. This means that for Apple Macintosh
computers using the Snow Leopard or later operating system, the USB Audio Driver from
Apple interfaces properly to the Alpha USB. It is not necessary to install a custom driver. This
is also true for newer versions of Linux, but not yet Windows. For optimum audio quality with a
Mac, use of high resolution music server software such as Audirvana, Pure Music or JRiver
Media Center is highly recommended.
Alpha USB Front Panel

Computer Configuration

Apple Macintosh Computers

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