Aphex Model 2020 Dynamics Processor

Sep 25, 2000

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Aphex demonstrated the new Model 2020 Dynamics Processor, which has been supplied to a number of other webcasters, including Westwind Media.com, ChristianPirateRadio.com, GratefulDead.com and Comedyworld.com. These and other organizations around the world are using Aphex dynamics-control units in front of data-compression systems that provide high-quality Real Media and Windows Media streaming audio and video content.

The Model 2020 is derived from the popular FM Pro 2020, which is becoming the system of choice of FM radio broadcasters. The Model 2020 is combination leveler, multiband compressor and peak limiter, self-contained in a single 2U rack mount chassis, and capable of being interfaced with external PCs; the unit incorporates over 12 Aphex patents in audio signal processing technology.

"Delivering high-quality audio through the very narrow pipe of the web is extremely difficult," explains Marvin Caesar, President of Aphex. "As in any audio chain, each link from source material to playback must be as clean and transparent as possible to achieve that quality level. Perhaps the weakest link in the webcaster's chain is the pipeline itself. Because there are severe bandwidth restrictions - as slow as 28.8 kbps for a dial-up connection - the audio must be heavily bit rate reduced." Such heavy data reduction introduces artifacts, and these artifacts can be reduced or made worse depending on the processing done in front of the encoder.

"Most listening to the web is done via small speakers on either side of a video monitor, and at fairly low levels," continued Caesar. "It would be unacceptable for audio levels to drop below the ambient noise, or to suddenly be blasting. Squeezing source material that has varying levels and dynamic characteristics into a fairly tight dynamic range is another challenge."

"Some of the most popular streaming media sites have selected Model 2020s to process their audio," added Caesar. "It provides average level control and an absolute peak ceiling while maintaining a natural, distortion-free sound. Because the processing is done in the analog domain, there are none of the aliasing problems generated by some digital processors. Those aliasing problems sound bad enough, but they also cause the encoders to have to work extra hard to cover up such artifacts."

The base Model 2020 features analog I/O, leveler, a four -band compressor, split band peak limiter and remote control software; system options include AES/EBU Digital In & Out, Pre-Emphasis Limiter and Stereo Generator plus Pre-Emphasis Limiter.

According to Marvin Caesar, "We transplanted some of our best circuits into the Model 2020, such as our high-performance, servo-balanced input and output stages, and our world-famous VCA 1001 voltage-controlled amplifier. But the processing algorithms are substantially new. Every stage of processing is crafted to work seamlessly with the next, so that there is no sense of competition or 'fighting' for control between the leveler, compressor and limiter elements. At every stage, the sonic effect of the process was carefully tuned for the minimum objectionable artifacts and maximum performance."

For more information, visit their web site at www.aphex.com.