Omega_FM Airchain Processor Adds Features

Audio processing has matured considerably since the days of the Gates Level Devil and CBS Audimax/Volumax, and the advances have most often been microprocessor-related.
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Audio processing has matured considerably since the days of the Gates Level Devil and CBS Audimax/Volumax, and the advances have most often been microprocessor-related.
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Easy to use, yet full-featured

Advanced users can access all parameter adjustments - nothing is hidden

Affordably priced

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A few reference charts in the manual would be helpful

Pilot output and RDS input jacks are missing

For more information from Inovonics, contact the company in California at (831) 458-0552 or visit www.inovon.com
The Inovonics Omega_FM Digital FM-Airchain Processor, now with software version 2.0, is diminutive in size at just 2RU, yet is a full-featured audio processor/stereo generator that uses a single-board computer or SBC to perform its "number-crunching" duties.

The SBC, a front-panel board, a pair of analog/digital I/O interface boards and a power supply are its principal internal components.

This simplified design approach differs from that found in common practice. According to Inovonics, "Processing is performed entirely within the digital domain without application-specific DSP chips or modules. No hardware upgrades are necessary for future updates."

That statement is proved true by the significant features added by software v2.0: an advanced AGC, a fourth parametric EQ section, bass enhancer, scheduler function and remote control via modem.

Unconventionally conventional

The equivalent block diagram on the Omega_FM illustrates familiar elements: AGC, parametric EQ, bass enhancement, leveling, compression, wideband and high-frequency limiting and spectrum-filtered composite clipping. But looking further, we learn how elements have been refined in a way that would be difficult to achieve without digital technology.

The Advanced AGC section uses a complex, multiple-slope level correction function to ride gain on the input signal and keep it within an optimal range for subsequent processing operations. Small level corrections are done slowly, but large changes are performed at an accelerated rate.

When the signal level falls below a preset level, the AGC returns to 0 dB (unity gain) rather than just gating at an inappropriate gain level. A rather unique feature is the ability to inhibit its gain function: The AGC will still reduce high-level signals, but low-level signals will not be amplified. This can be extremely useful in classical and sports formats where it might be undesirable to raise low-level signals.

Four independent, yet identical sections of state-variable parametric equalization allow for precise sound tailoring. Center frequency is adjustable from 50 Hz to 20 kHz, Q from 1 to 5, and amplitude from -10 to +10 dB. Because EQ sections do not always combine in a predictable manner, a graph shows the resulting curve along with the response of each EQ section.

A psycho-acoustic bass enhancement circuit is said to accentuate and phase-align harmonic components of low bass fundamental frequencies using a proprietary algorithm. Not to be confused with parametric or other EQ, this feature increases perceived bass without a corresponding increase in peak modulation.

Even though this enhancement is audible on all speakers - large and small - vehicle sound systems in particular will notice the effect.

In radio, there is certainly no shortage of "EQ-rich" or "spectrally diverse" source material. Because most stations favor a degree of uniformity, four-band leveling section of the Omega_FM works to minimize the differences. Described as a multiband AGC, leveling is slow, unobtrusive and gated.

The four-band compression section is in part responsible for increasing program density, which is a major contributor to perceived loudness. It operates at a rapid rate to reduce the amplitude range and provide dynamic graphic equalization of the signal.

Peak limiting is two-tiered using separate wideband and high-frequency processes to assure absolute peak control. Dynamic operation of the wideband section is controlled by a floating gain platform that allows fast release of instantaneous peaks to the platform value, while the platform itself releases at a slower rate. Meanwhile, the downstream high-frequency limiter subdues high-frequency peaks, especially those caused by pre-emphasis.

Finally, adjustable composite clipping with spectrum filtering further improves loudness. Sometimes shunned because of potential ill effects, composite clipping can significantly increase loudness. But, without proper implementation, there can be a penalty to pay that includes pilot modulation and spurious emissions well outside spectrum of the composite signal.

According to company literature, "The Omega_FM incorporates a unique output filtering algorithm that protects both the 19 kHz stereo pilot and the spectrum above the 53 kHz top edge of the multiplex signal."

Powerfully simple

The device caters to novices because of its straightforward operation, but advanced users will no doubt like its level of tweakability.

Fourteen LED meters display input level, AGC, leveling, compression and limiting action and output level. Four pushbutton switches allow you to select from factory-programmed processing presets. Absent are jog wheels and soft keys.

Rather than format-specific options, the user can select from Light, Medium and Heavy processing versions of Natural, Smooth and Aggressive signatures. These nine choices support a surprising range of possibilities from subtle to audacious. If one preset is not the perfect one for your format, it will certainly serve as a well-defined starting point.

The flexibility of the Omega_FM will reveal itself when a compatible PC is connected to the front-panel DB-9 connector (or remotely via modem). Using supplied software, the user has access to the full range of controls - nothing is hidden or inaccessible.

You can adjust the AGC (attack, release, gate threshold, maximum gain, etc.), EQ, multiband (drive level; leveling attack, release, threshold, rest level; compression drive, attack, release; band output; and bass enhance), limiter (wideband drive and time constants; limiter balance; high frequency limiter time constants; and pre-emphasis), multiplex (clip point and filtering), and numerous other options - I counted a total of 47 processing parameters (excluding EQ). A signal generator is included for setup.

On the rear panel are 10 connectors: analog inputs and outputs (XLR), digital input and output (AES/EBU on XLR, S/PDIF on BNC), analog composite output (BNC) and a DB-9 connector for remote modem access.

Out of the box

Due to its overall simplicity, the Omega_FM was installed and on the air faster than any other processor I have worked with in recent times. And one of the factory presets proved to be an excellent starting point. The software was easy to navigate, and allowed me to dial in on the exact air sound that pleased the PD and air talent alike, which I saved as a custom preset.

Even with moderately aggressive processing, it is clean and crisp, without the grunge or shrillness sometimes associated with digital processing. It is competitively loud and the spectrum above 53 kHz is as comparably clean as other processors I have used.

One of the biggest challenges of an audio processor is the human voice. Both male and female voices are natural-sounding, and I have found it unnecessary to preprocess the condenser microphones.

The short signal path and software-based processing contribute to the device's modest latency (program signal delay) of 10.5 ms, which has created no problem for our air talent who monitor off-air while on microphone.

The manual, which is amusing at times, thoroughly explains the nuances of audio processing and the complexities of the Omega_FM in an easy-to-read fashion. Despite its completeness, a chart that summarizes key adjustments and their effect (e.g. "if you want a brighter sound, reduce HF Attack time") might prove helpful for those who are intent on finessing the unit to the ultimate point of perfection.

A missing feature that has been long on my wish list is a band output solo function. While it is essential that you listen critically to the entire mix, being able to monitor individually the output of each processing band could aid in one's fine-tuning efforts. I would also like to see pilot output and RDS input jacks added.

Audio processing will continue to be subjective, and competition remains fierce. During bench and on-air tests, the Omega_FM without fail proved itself a formidable contender. Despite its surprising low list price of $5,880, the Omega_FM is a full-featured processor capable of producing a highly competitive air sound.

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