Radial USB-PRO Stereo USB - Computer Digital DI Box - Audio Interface

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The Radial USB-Pro is a high-resolution stereo direct box designed to convert sound files from a laptop computer and seamlessly transfer them to a pair of balanced audio outputs to feed a PA, recording or broadcast mixing console.

The USB-Pro started as a simple digital to analog converter for professional audio engineers.....

The Radial USB-Pro is a high-resolution stereo direct box designed to convert sound files 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
Made to be plug & play easy to use, the USB-Pro automatically configures itself for use with all popular operating systems including Mac OSX, Windows XP, Vista and Windows 7, thus eliminating the need to load special drivers. Connection from the laptop is done via the 'pro-audio standard ' USB type-B port.

Headphone Monitoring, Mono-Sum and Ground Lift
Digital-to-analog conversion is monitored with the built-in headphone amplifier to ensure the signal is being properly downloaded and converted. A mono-sum switch may be engaged to check for phasing or facilitate signal distribution to two outputs should this be preferred. One simply sets the output volume control to suit. Should hum or buzz caused by ground loops be encountered, two 'set & forget' side-access switches let you insert isolation transformers into the signal path to block stray DC voltage offsets. To further reduce susceptibility to noise, this is augmented with a ground lift switch that lifts pin-1 on the two XLRs.

24-Bit 96kHZ Digital to Analog Converter
As a USB direct box, USB-Pro's job is to convert a digital audio file to a pair of XLR outputs. Keep in mind that a direct box is supposed to be mic level so that it can properly live along side microphones and be processed using the same mic splitters, active distribution systems and mixing consoles without causing problems such as crosstalk or distortion. Unlike devices that are limited with 16 bit, 44.1kHz conversion rates, the USB-Pro elevates the performance with true 24 bit, 96kHz stereo converters to deliver more headroom and greater detail. This eliminates the need for additional sound cards or separate converters when transferring files, further streamlining production in busy work environments.

Trademark Radial Quality
As with all Radial products, the USB-Pro is designed to handle the rigors of professional touring. Our unique book-end design creates protective zones around the switches, connectors and controls to keep them out of harm's way. Inside, our time-tested I-beam construction assures the sensitive internal PC board will not torque which could otherwise cause premature part failure. Finally, a full bottom no-slip pad provides mechanical isolation and electrical insulation, further advantaging the user.


  • High performance 24bit/96k stereo direct box
  • Automatically installs without the need of a driver
  • Built-in headphone amplifier for monitoring
  • Balanced Lo-Z outputs with switchable isolation


Using the USB-Pro with a laptop

Nothing is simpler than the USB-Pro! You plug it into your laptop and it automatically delivers your digital audio files to spectacular sounding stereo audio via the 24 bit/ 96kHz converters. You merely connect to the mic inputs on your mixing console and you are set to go!

Using the USB-Pro in the studio

Convert your client's files instantly! Simply connect the laptop to the USB-Pro and transfer files to the recording system at the maximum sample rate for best audio fidelity. The built-in headphone amp makes it easy to check for signal integrity.

Using the USB-Pro for a video presentation

Anyone that has incorporated audio with a projector knows that noise can be a serious problem. The USB-Pro is equipped with isolation transformers that may be switched in to eliminate hum and buzz caused by stray DC voltage and ground loops.


Audio circuit type: Custom decoder with analog line drive
USB compliance: USB 2.0 full speed
Bit depth: 24bit (16bit capable)
Sampling rate: 96kHz (44.1kHz / 48kHz auto sensing)
Sound file compatibility: WDM, MME, ASIO, CoreAudio and DirectSound
Software compatibility: Windows XP/Vista/Win7 and Mac OS
Frequency response: 5Hz ~ 40kHz (30Hz ~ 18kHz with isolation)
Dynamic range: >90dB
Noise floor: -90dB
Maximum gain: +8dBu
Total harmonic distortion: 0.01%
Stereo separation: 75dBu
Output impedance: 300? nominal
Specifications are subject to change without notice.



Digital input: USB connector B-type
Analog output: Stereo balanced mic level (2 x XLR-M)
Headphone output: 3.5mm TRS
Level control: Variable, works on headphone and XLR outputs
Isolation: Switchable for each channel
Mono switch: Sums left & right inputs to mono
Ground lift: Lifts pin-1 on both XLR outputs



Power: USB bus powered 500mA maximum
Construction: 14 gauge steel chassis and outer shell, baked enamel finish
Size: 3.3" x 5.0" x 2" (84 x 127 x 48mm)
Weight: 1.5 lb (680 g)
FCC approval: Complies with section 15 of the FCC Rules
Conditions: For use in dry locations only between 5°C and 40°C
Warranty: Radial 3-year, transferable


View PDF brochure for Radial USB-PRO Stereo USB - Computer Digital DI Box - Audio Interface
By: on 10 July 2014
This is another instance where Swamp delivered really promptly at a price that was competitive with other online suppliers ...but where I've waited until several months of "bashing around" had been completed before submitting a review of this ground-breaking (literally and figuratively) product from Radial of Canada's alchemists of audio.

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