Field Report: Vorsis AP-2000


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The GUI was designed so navigation is done with no more than two mouse clicks — no more auguring through multi-branched menu trees. It can control any number of AP-2000s over a LAN through VPN tunnels and behind firewalls. Any laptop or desktop computer running Windows 2000 or XP with a CPU speed of 1GHz should perform just fine. The Web interface does not support open ports to the Internet or act as a Web server making it immune to network hacking.

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The GUI display is divided into four basic sections: Title Bar, Control Area, Side Bar and Dynamic Displays. Dynamic Displays region includes a frequency-domain graph showing the parameters of the five-band AGC, both FM and HD 31-band limiters and the adjusters for manipulating settings.

On the left hand side of the Dynamic display are a series of four bar graph meters for monitoring input/output levels and processing levels. The Gain Reduction Meter can be selected to monitor a variety of internal processes.

Fast-Fourier Transform (FFT), real-time spectral analysis is available at the click of a button to display the input audio or the processed audio. Various other display parameters such as an oscilloscope representation of the signal, gain reduction graph and control position markers can be selectively added or removed from the display.

Control Area

A large area above the Dynamic Display is the Control Area. Under the Input panel you will find adjustments for selecting analog vs. digital audio sources, engaging the input failsafe feature, independent gain control for the analog and digital sources, balance trim as well as controls for auto mono, phase rotator, Voice Master and the high pass filter.

The auto mono feature, as the name implies, was developed to clean mono content where unintentional artifacts cloud the spatial image. The phase rotator prevents clipping by rearranging the phase of asymmetrical waveforms before they hit the rail. The high-pass filter eliminates low frequency content that cannot be heard on FM and is a source of intermodulation distortion.

A Vorsis exclusive is the Voice Master algorithm. It engages a special voice-specific set of equalization and limiting parameters when it detects mono, narrow bandwidth and asymmetric waveforms. If all three of these parameters are met the Voice Master engages.

The four-band parametric equalizer could be described as a four control node EQ. These fully independent but complementary control nodes can be frequency centered anywhere in the audio spectrum, even stacked. Each node can be adjusted for bandwidth and Boost/Cut. The EQ can be electronically inserted before or after the five-band AGC section.

Core audio processing is divided into three sections: the SST, AGC and compressor. While the AGC and compressor work in a traditional fashion, it is the Sweet Spot Technology (SST) that smoothes processing performance over the long haul, making sure that program content has a consistent sound regardless of the program material. Where AGC and compressor address instantaneous events, the SST acts as the intelligent gain riding control from program element to program element.

The Vorsis/Wheatstone website contains a wealth of information including support documents and software downloads. Jeff Keith, head of the Vorsis design team, has authored a number of white papers explaining the theory behind each algorithm.

Out of the box

Our facility had the opportunity to examine the AP-2000 first hand as well as its predecessor, the AP-1000. It was bench-tested and placed in the broadcast chain of our hot country station for about a week.

Whether you're the intuitive type to simply plug things in and make them work or wait till you've scoured the manual, the GUI was intuitive and easy to navigate. Most controls are mouse-based with some parameters that can be entered via the keyboard. Having every control within two mouse clicks does make it a bit easier to change parameters.

My director of engineering was impressed with the limiter and AGC controls but especially the parametric EQ. The click-and-drag method for changing frequency, gain/loss and bandwidth is pretty cool.

The sheer number of variables that go into shaping the final product can be a bit daunting. Finding the best balance among the various limiters and clippers along the way can take time. In the week the AP-2000 was in chain, many different preset styles were tried with relatively good results.

It's probably impossible to find the perfect sound overnight. Processing is a subjective art and one can become lost after listening intensely for a while. Every audio processor has its signature sound, as does this one. It has some pretty powerful features and evaluating it was like going back to school.


Chestnut is assistant chief engineer at Entercom Kansas City.


Editor's note: Field Reports are an exclusive Radio magazine feature for radio broadcasters. Each report is prepared by well-qualified staff at a radio station, production facility or consulting company.

These reports are performed by the industry, for the industry. Manufacturer support is limited to providing loan equipment and to aiding the author if requested.

It is the responsibility of magazine to publish the results of any device tested, positive or negative. No report should be considered an endorsement or disapproval by Radio magazine.




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