Aphex Systems 320A owner manual Appendix E, Compellor to the Rescue

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Appendix E

In a world where all audio levels would be monitored by VU meters, this SMPTE standard would make things simple. Since VU meters measure something close to the average level, we could simply equate 0VU to -20dBFS with a calibration tone. We could mix and track on the VU meters, knowing there is 20dB of headroom in the digital domain for peaks. Since most audio has peaks that go 10 to 14dB over the average level, then we would still have 6 to 8 dB of digital headroom left over to allow for subsequent digital overshoots. However, most of the digital gear is shipped only with peak responding dBFS meters, not VU meters. When working only with dBFS meters, it is not possible to apply the SMPTE standard, and therein lies the confusion.

Early in digital audio history, the manufacturers of DAT recorders taught everybody to record at an average level of -18dBFS, but they forgot to tell you something important. They forgot to tell you that the -18dB should be the actual average level, not the running average of the peak levels. Unfortunately, the DAT machines only come with dBFS metering, and people went around recording peak levels way down in the mud - at least 10dB too low for good digital quality. That’s why so many DAT recordings sound like crap.

That’s not the worst of it. With no other sources of edification, recordists and engineers have applied the same principle in other digital audio work. This has led to a serious problem in the recording industry where tracks and mixes are ridiculously variable in level and quality. You will find CD’s that were mastered with peaks slamming against 0dBFS and clipping all to hell. You can also find CD’s mastered so peaks hardly ever exceed -8dBFS. These discrepancies reveal the widespread problem of misunderstanding the technology.

COMPELLOR TO THE RESCUE

A Compellor can make necessary corrections to the average levels in a peak referenced system, either analog or digital. Remember, though, that a PPM or dBFS indication of the Compellor’s output will not appear as consistent as the input. The average output level as seen on a VU meter certainly will be more consistent. As explained previously, this is the natural result of level averaging - the desired processing effect - and should not be misinterpreted as a problem.

If, after the average levels have been corrected by a Compellor, it is felt the PPM or dBFS indications should be made more consistent, you can use an Aphex Dominator “Precision Multiband Peak Limiter” after the Compellor. The Dominator will not act on the average levels but will transparently control the peaks and bring the program closer to having consis- tent peak levels without disturbing the average levels. The Compellor and Dominator are designed to work together and no other peak limiter will perform with equal transpar- ency to the sound quality.

Since the Compellor’s reference system is average, you will not be able to find a direct match- ing REF LEVEL setting for a peak referenced system. However, remembering that averages are usually 10 to 12 decibels below the peak level of typical sound, you can use the -10dBV setting on the Compellor to get a reasonable match for peak references of about 0 to +6dBu (-10dBV equals -7.8dBu).

An excellent way to set the Compellor’s REF LEVEL switch is to pass a signal through the Compellor at standard levels and observe the input level meter on the Compellor. The red bar part of the indication is similar to a VU indicator. Select a REF LEVEL switch setting that brings the red bar closest to hitting 0VU.

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Contents 320A Fast Finderi Safety Declarations320A Contents Page Quick Start Quick StartBit Of Compellor History What Is a Compellor?What Does It Do? How Does It Work?Introduction Page Mains Voltage Selection And Fuse UnpackingDamage & Claims Proper Ventilation Power CordSafety Considerations Mounting In a RackInput Connections InstallationRemote Connector Reference Level SettingSummary Specications Ratio Mastering IntroductionRecording MixingBroadcast Radio Pre-processing Video Post-ProductionLive Concerts Voice Processing Broadcast STL/ Phone Line DriverTelevision Broadcasting and Cable Systems Video and Audio Tape DuplicationHard Disk Recording Leveling Function Signal FlowProcessing Functions Silence Gate Compressor FunctionDRC DVGLimiter Stereo EnhanceStereo Linking Meter SelectionsOperating Levels Process SwitchOutput Control Input/OutputGain Reduction Metering To Obtain Service Limited WarrantyAppendices Appendix B 320A Appendix C Appendix C Proper Wiring TechniquesAppendix D Part 1 Balanced OUT to Balanced Appendix DImpedance Balanced Outputs Part 5 Y Insert Cables Appendix E Compellor to the Rescue Appendix EPPM Standard Where The Problem Comes FromAppendix F ConfusionVU Standard Appendix FDAT Tragedy Where The Compellor FitsDeath of a Perfectly Good VU Meter Birth of dBFSAnalog/Digital Level Discrepancy Ideal Audio PackageWhat, Me Worry?

320A specifications

The Aphex Systems 320A is a dynamic processor designed to enhance the quality of audio recordings in professional settings. Known for its exceptional performance and versatility, the 320A offers a unique combination of compression, limiting, and expansion functionalities. This unit is an essential tool for sound engineers and producers looking to achieve polished sound.

One of the standout features of the 320A is its dual channel processing capability. This allows users to apply dynamic processing to two separate audio signals simultaneously, making it ideal for stereo or dual mono setups. The 320A offers a range of controls, including threshold, ratio, attack, release, and gain, allowing precise adjustments to be made according to the needs of any project.

The 320A utilizes Aphex's proprietary Intelligent Clipping technology, which helps to prevent distortion at high signal levels. This feature is particularly beneficial when working with dynamic sources like vocals and percussive instruments. Intelligent Clipping ensures that the audio remains smooth and clear, even when processed aggressively.

In terms of connectivity, the Aphex 320A is equipped with balanced XLR and TRS inputs and outputs, ensuring compatibility with various audio sources and devices. The unit supports both line-level and mic-level signals, providing flexibility for different recording scenarios. Additionally, its low noise operation ensures that the final output retains pristine audio quality.

Another significant characteristic of the 320A is its user-friendly interface. The front panel features easy-to-read meters and clearly defined controls, making it straightforward for users to monitor the audio levels and adjust settings in real-time.

The 320A also includes a sidechain capability, allowing users to trigger compression or expansion from an external source. This feature is useful for achieving effects like ducking or creating rhythmic dynamics in a mix.

In summary, the Aphex Systems 320A is a feature-packed dynamic processor that serves as an invaluable tool for audio professionals. With its dual channel processing, Intelligent Clipping technology, flexible connectivity options, and user-friendly design, the 320A stands out in the realm of audio processing equipment, delivering high-quality performance for a variety of recording and mixing applications.
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