Radial Engineering Ltd.
USB-Pro™
True to the Music
®
1
oVErVIEW
The Radial USB-Pro is a fully USB 2.0 compliant, 24bit digital to analog
audio converter and professional direct box in a compact and road
rugged package.
A typical direct box is a device that lets you interface a high impedance
(hi-Z) audio output with professional low impedance (low-Z) PA and
recording systems. In the case of the USB-Pro, the digital audio signal
is controverted to analog and feeds directly into the direct box circuit
to produce low-Z balanced left and right stereo signals. The built in
preamp allows you to adjust the output level from mic-level to line-level
and enables the USB-Pro to connect directly to mixing consoles, power
amplifi ers and self-powered speakers alike. The USB-Pro ensures the
digital signal is delivered to the PA as faithfully as possible.
LEFT
CHANNEL
RIGHT
CHANNEL
MAC or PC
PA SYSTEM
USB-Pro
DIGITAL USB
INPUT
The USB-Pro is very easy to setup and use because it derives power
from the USB connection and automatically confi gures the sampling rate
and bit depth without the need for special drivers. The USB-Pro can be
used for audio playback, system testing and for transferring digital audio
fi les to analog for processing.
Following the block diagram below, a computer’s USB digital audio output
is converted to analog audio. A level control allows you to adjust the output
level and a mono sum switch can be activated to send mono signals to
two separate audio systems or check for phase issues. The 3.5mm mini-
headphone output can be used to monitor the stereo signal. Before the
XLR output, isolation transformers may be switched into the circuit to
eliminate noise caused by ground loops. The signal is then balanced to
drive long cables without inducing noise.
DIGITAL TO
ANALOG
USB
INPUT
LAPTOP
RADIAL USB-Pro
HEADPHONE
AMP
HEADPHONE
3.5MM OUT
LEVEL
CONTROL
MIC TO LINE
STEREO /
MONO SUM
TRANSFORMER
ISOLATION
BALANCED
XLR OUT
