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®
True to the Music
USB-PRO
USB Direct Box
™
User Guide
®
Radial Engineering Ltd.
1588 Kebet Way, Port Coquitlam BC V3C 5M5
tel: 604-942-1001 • fax: 604-942-1010
info@radialeng.com • www.radialeng.com
True to the Music
www.radialeng.com
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®
™
Radial USB-PRO
USB to Audio Direct Box
Table of Contents Page
Overview .........................................................................1
What is a direct box anyway ............................................1
Features ...........................................................................2
Getting started with USB and audio connections ............3
Testing and Using ............................................................4
Eliminating hum and buzz ................................................4
Using the headphone output ............................................5
Specifi cations ..................................................................5
Radial Limited Warranty ...................................Back Cover
INTRODUCTION
Congratulations on your purchase of the Radial USB-Pro! The Radial
USB-Pro is a high-resolution stereo direct box designed to convert sound
fi les from a laptop computer and seamlessly transfer them to a pair of
balanced audio outputs to feed a PA, recording or broadcast mixing
console.
Plug and play easy to use, the USB-Pro can be up and running in no time.
That said, as with any new product, we recommend that you take a little
time to read through the manual in order to familiarize yourself with the
USB-Pro features so you can get the most out of it.
If you have any questions that are not covered in this manual, please
consult the FAQ section on the web site as this is where we post the latest
updates and questions from other users. If you still can’t fi nd what you are
looking for, feel free to send us a note at info@radialeng.com and we will
do our very best to reply in short order.
Now get ready to sing along at 96kHz!
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True to the Music
OVERVIEW
The Radial USB-Pro is a fully USB 2.0 compliant, 24bit/96kHz 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 convertered to analog and feeds directly into the direct box circuit
to produce low-Z balanced left and right stereo signals. These outputs
connect to a mixing console which in turn feeds the PA system. Direct
boxes like the one built into the USB-Pro ensure the signal is delivered to
the PA as faithfully as possible.
LEFT
DIGITAL USB
INPUT
CHANNEL
RIGHT
CHANNEL
MAC or PC
PA SYSTEMUSB-Pro
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 separate left and right stereo channels. A level control
allows you to make fi ne adjustments and a mono sum switch can be
activated to test for phase issues or send mono signals to two separate
audio systems. 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 back to the mixing console.
USB PORT
ON LAPTOP
Radial Engineering Ltd.
D TO A
CONVERTER
LEVEL AND
MONO SUM
1
HEADPHONE
OUT
BALANCED
XLR OUT
USB-Pro™
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FEATURE SET
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2 3 4 65
1
7
8
1. LEVEL: Used to set the XLR and headphone output level.
2. MONO: Sums the stereo signal to mono. When active, the LED
indicator illuminates. Mono mode reduces the channel count on
the PA or lets you send the signal to two separate audio systems
simultaneously.
3. HEADPHONE: Mini 3.5mm (1/8”) TRS headphone output is used
to check the output from the digital source for trouble shooting.
Works with ear-buds and standard headphones.
4. USB PORT : Connects from the PC or Mac using a TYPE B cable.
This port delivers the digital audio signal and power to the USBPro which automatically recognizes the sample rate and bit depth.
5. POWER LED: This indicator will illuminate when the power is
received from the USB connection.
6. LEFT XLR OUT: Standard XLR male output follows the AES
format with pin-1 ground, pin-2 hot, pin-3 cold.
7. GROUND LIFT: Used to help eliminate hum and buzz caused by
ground loops. Lifts pin-1 on both XLR outputs.
8. RIGHT XLR OUT: Standard XLR male output follows the AES
format with pin-1 ground, pin-2 hot, pin-3 cold.
9. ISOLATION: Switches on side panel for each channel lets you
insert transformers isolation when needed. Use to eliminate hum
and buzz caused by ground loops.
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Radial Engineering Ltd.
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USB-Pro™
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True to the Music
GETTING STARTED
Before making any connections, always ensure your audio system
is either turned down or turned off in order to protect more sensitive
components from damage due to loud turn-on or plug-in transients.
USB CONNECTION
The Radial USB-Pro is powered by
your computer’s USB port. As soon
as you plug it in, the USB-Pro will
power up and automatically confi gure
itself based on your computer’s audio
settings. The POWER LED indicator
will illuminate to let you know the USBPro is up and running.
LED Power Indicator
As the USB-Pro uses a TYPE B USB
connector, you will need a USB 2.0
cable that fi ts the USB port on your
computer or laptop. This will most
likely be a common ‘TYPE A to TYPE B’
USB cable that is compatible with the
majority of personal computers and
TYPE A USB
Fits most laptops and computers
laptops.
Many other USB adapters and cables
are available to connect tablets, USB
hubs and other USB devices to the
USB-Pro. Check with the manufacture
of your device to determine the correct
USB cable that is needed to fi t your
TYPE B USB
Used to connect to the USB-Pro
device.
AUDIO CONNECTIONS
Connect two standard low-impedance XLR cables from the LEFT and
RIGHT outputs to the mic inputs of your PA or recording system. These
XLR outputs comform to the AES standard and are balanced to drive
long cable runs up to 100 meters (300’) without noise and are suitable
to connect the USB-Pro to professional mixing consoles and preamps.
RIGHT
LEFT
Audio connections for PA system and recording systems use
balanced XLR cables up to 100 meters (300’).
Radial Engineering Ltd.
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USB-Pro™
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True to the Music
TESTING AND USING
First, set the USB-Pro’s LEVEL control to
the 12 o’clock position. This will allow you
to adjust the output level on the fl y . Next,
check the status of the MONO SUM
LEVEL
MONO
SUM
switch and LED indicator. For stereo,
set the switch to the outward position
(LED off). For dual mono outputs, set the
MIN MAX
switch to the inward position (LED on).
It’s a good idea to start testing your computer’s audio with a sound fi le,
MP3 or video you are framiliar with. Set your computers output level and
the level of the media playback software to approxmimatly 80%. Keep
in mind that various media fi les will playback at different volume levels
depending on your software and how the sound fi le was recorded.
Slowly raise the level of the PA or recording system. It is good practice
to always test at a low volume to ensure proper connections have been
made and all devices in the signal chain are set up correctly and working.
This way, should a device not be turned on or a connection not fully made,
it will not create a loud transient ‘pop’ in the PA which could damage
a tweeter or annoy your audience. When satisfi ed, slowly increase the
input gain on your mixing console until you reach an appropriate level.
In some cases, like when a second audio interface is also connected
to your computer alongside the USB-Pro, your computer may not
automatically switch to the USB-Pro as the main audio output. In such
cases you will need to enter your computer system’s control panel and
select the USB-Pro as the audio output device from a list of available
devices.
ELIMINATING HUM AND BUZZ
The USB-Pro has been designed to
minimize hum and buzz caused by
ground loops by incorporating dual
isolation transformers for the XLR
outputs. The isolation transformers
are normally bypassed but may be
introduced into the signal path using
the side access ISO switches. If you
hear noise after connecting the USBPro to your audio system, try engaging
the isolation transformers by sliding the
switch in the direction of the arrow.
This is supplemented with a ground LIFT
switch located next to the XLR outputs.
When set to the inward position, this
switch disconnects pin-1 from the two
XLR’s.
Radial Engineering Ltd.
4
Left & right transformer
isolation switches
Ground Lift
USB-Pro™
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LEFT
RIGHT
GROUND
True to the Music
USING THE HEADPHONE OUTPUT
The USB-Pro is also equipped with
a stereo headphone output. The
headphone amplifi er taps the signal
directly from the digital audio converter
and can be used at the same time as the
balanced XLR outputs. The 3.5mm (1/8”)
output is designed for both ear buds
and standard TRS stereo headphones
where tip-left, ring-right and the sleeve is
ground.
Be Careful, the USB-Pro is designed for professional use as the
headphone amp is very powerful and is capable of high sound levels
when driven to maximum. Always ensure the output level of your
computer, laptop or tablet is set at an appropriate level before auditioning
music through headphones. This will not only save your ears, but save
the ears of your client! *See caution note on the back page.
BLOCK DIAGRAM
OUTPUT
LEVEL
LEFT
OUT
USB
RECEIVER
RIGHT
OUT
FILTER
MONO
FILTER
TRANSFORMER FULL BYPASS SWITCHES
H/P
AMPLIFIER
OUTPUT
LEFT
OUTPUT
RIGHT
HEADPHONE
OUTPUT
SPECIFICATIONS*
Audio circuit type: .................................................DAC with balanced outputs
Compatible with: .................................. Windows XP/Vista/Win7 and Mac OS
Supports: ............................ WDM, MME, ASIO, CoreAudio and DirectSound
Sampling rates: .......................Set by computer OS 44.1/48/96kHz; 16/24bits
Frequency response: ................................................................ 20Hz ~ 20kHz
Total harmonic distortion: .....................................................................<0.01%
Dynamic range: .......................................................................................90dB
XLR output impedance: ................................................................... 250 Ohms
Stereo channel separation:.......................................................................75dB
XLR confi guration: .........................................Pin 1 ground, Pin 2 (+), Pin 3 (-)
USB bus power:....................................................................525mA maximum
USB connector: ..................................................................Type-B USB input
Construction: ......................................14 gauge steel chassis and outer shell
Finish: ........................................................................................Baked enamel
Warranty: ...............................................................Radial 3-year, transferable
*Specifi cations are subject to change without notice.
Radial Engineering Ltd.
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GROUND LIFT
USB-Pro™
CHASSIS
GROUND
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THREE YEAR TRANSFERABLE LIMITED WARRANTY
RADIAL ENGINEERING L TD. (“Radial”) warrants this product to be free from defects in
material and workmanship and will remedy any such defects free of charge according
to the terms of this warranty. Radial will repair or replace (at its option) any defective
component(s) of this product (excluding fi nish and wear and tear on components under
normal use) for a period of three (3) years from the original date of purchase. In the event
that a particular product is no longer available, Radial reserves the right to replace the
product with a similar product of equal or greater value. In the unlikely event that a defect
is uncovered, please call 604-942-1001 or email service@radialeng.com to obtain an
RA number (Return Authorization number) before the 3 year warranty period expires.
The product must be returned prepaid in the original shipping container (or equivalent)
to Radial or to an authorized Radial repair center and you must assume the risk of loss
or damage. A copy of the original invoice showing date of purchase and the dealer name
must accompany any request for work to be performed under this limited and transferable warranty. This warranty shall not apply if the product has been damaged due to
abuse, misuse, misapplication, accident or as a result of service or modifi cation by any
other than an authorized Radial repair center.
THERE ARE NO EXPRESSED WARRANTIES OTHER THAN THOSE ON THE FACE
HEREOF AND DESCRIBED ABOVE. NO WARRANTIES WHETHER EXPRESSED
OR IMPLIED, INCLUDING BUT NOT LIMITED TO, ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE SHALL EXTEND
BEYOND THE RESPECTIVE WARRANTY PERIOD DESCRIBED ABOVE OF THREE
YEARS. RADIAL SHALL NOT BE RESPONSIBLE OR LIABLE FOR ANY SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES OR LOSS ARISING FROM THE USE
OF THIS PRODUCT. THIS WARRANTY GIVES YOU SPECIFIC LEGAL RIGHTS,
AND YOU MAY ALSO HAVE OTHER RIGHTS, WHICH MAY VARY DEPENDING ON
WHERE YOU LIVE AND WHERE THE PRODUCT WAS PURCHASED.
Headphone Safety Warning
Caution: Very Loud Amplifi er
As with all products capable of producing high Sound Pressure Levels (SPL)
users must be very careful to avoid the hearing damage that may occur
from prolonged exposure. This is particularly important as it applies to
headphones. Prolonged listening at high SPLs will eventually cause tinnitus
and can lead to partial or complete loss of hearing. Please be aware of the
recommended exposure limits within your legal jurisdiction and follow them
very closely. The user agrees that Radial Engineering Ltd. remains harmless
from any health effects resulting from the use of this product and the user
clearly understands that he or she is entirely responsible for the safe and
proper use of this product. Please consult the Radial Limited Warranty for
further details.
®
www.radialeng.com
Radial Engineering Ltd.
1588 Kebet Way, Port Coquitlam BC V3C 5M5
tel: 604-942-1001 • fax: 604-942-1010
info@radialeng.com • www.radialeng.com
Radial® USB-Pro™ User Guide - Part# R870 1224 00
Specifi cations and appearance are subject to change without notice.
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