Scientist's in the 1950's believed the home
PC would look like this.

Radial's unique I-beam construction for
maximum durability.

Comparing the resolution between
16bit and 24bit converters.

Using the USB-Pro in a studio
with headphones.

USB-Pro™ Development

We hate digital! not the sound, but the problems associated with ever changing standards, Mac and PC conversion issues and so on. So for Radial to finally succumb to the digital allure, we waited until we felt the market was truly stable. The advent of self-initiating USB software was the tipping point. In other words, because special drivers were no longer required for all of the various computers, we felt the time had come to jump into the digital pool.

The USB-Pro started as a simple digital to analog converter for professional audio engineers. It is worth underscoring that the difference between a professional and an amateur is not merely gauged on ability... it is about getting the job done and making sure the job is done to completion. Point being: when you have 20,000 screaming fans in an arena, saving $100 on a low cost interface is not the priority. If the audio system goes down, you now have 20,000 headaches to deal with! At Radial, we build products for professionals, so our primary concern is performance.

Establishing the feature set

As a USB digital audio converter and direct box, USB-Pro's job is to convert your computer audio playback to a pair of XLR outputs. As a direct box, it will output microphone level so that it can utilize the same splitters, active distribution systems and mixing consoles without causing problems such as crosstalk or distortion. As a line level driver, it will [ output a balanced line level signal that can feed amplifiers or powered speakers directly.

When considering how the USB Pro would be used in the professional environment, the decision was made to add isolation transformers. Computers, projectors and other consumer equipment can be particularly noisy, so transformers can be incredibly useful when combating system noise. The downside to transformer isolation is that they inevitably limit the bandwidth and dynamic range. Considering most PA systems are not capable of faithfully reproducing audio below 30Hz or above 15kHz the reduced bandwidth would not be noticed in most applications, but unacceptable in others. We concluded that so long as the transformers could be taken out of the signal path when not needed, they would be beneficial. So we added a couple of recessed set & forget slider switches on the side to facilitate the isolation when needed.

The next feature we added was a mono-summing switch. This presents several benefits: When connecting to a mono sound system, you can ensure that the combined left and right stereo signal is heard. Once set to mono, the same signal is routed to both outputs to feed two separate audio systems. Since the two outputs can be individually transformer isolated, most of the noise problems caused by ground loops are eliminated. A ground lift switch on the outputs takes this one step further by lifting pin-1 on the XLRs. Computers are often the source for noise problems in audio systems, so greater care is certainly needed to keep things quiet.

Final touches included a power-on LED to let you know the USB-cable is properly connected as this is where the USB-Pro derives its power. Another LED lets you know if you are set to mono. And there is a simple gain control on the front panel for quick level adjustments.

We hate digital... but we have grown to love the USB-Pro. We think you will too!