Radial Engineering Ltd.
USB-Pro™
True to the Music
®
TESTIng And uSIng
First, set the USB-Pro’s LEVEL control to
the 7 o’clock (off) position. This will allow
you to adjust the output level on the fly.
Next, check the status of the MONO SUM
switch and LED indicator. For stereo, set
the switch to the outward position (LED
off). For dual mono outputs, set the switch
to the inward position (LED on).
It’s a good idea to start testing your computer’s audio with a sound file you
are familiar with. Set your computers output level and the level of the media
playback software (if applicable) to approximately 80%. Keep in mind that
various media files will play back at different volume levels depending on
your software and how the sound file was recorded.
Slowly raise the output level of the USB-Pro. 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 satisfied, 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 USB-
Pro 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.
4
OUTPUT LEVEL
SUM
MONO
POWER
LINE
DIGITAL INPUT
USB
left & right transformer
isolation switches
ground lift
