Easy To Use

The Model 320A provides the option of Dual Mono or Stereo operation. In the mono mode, you have two completely independent channels of processing to accommodate independent monaural signal feeds. In the Stereo mode, you can choose between linking only the leveling control signals or you can link both the compression and leveling signals. An intuitive front panel metering system displays input level, output level or gain reduction levels. All potentiometers are detented for accurate resetting of controls. A Leveling Speed (fast/slow) switch is located on the front panel, as is the defeat switch for the peak limiter. Operating reference levels are selectable from -10dBV, +4dBu or +8dBu. An RJ-11 connector is located on the rear panel to facilitate remote relay bypass of the unit.

• Intelligent Automated Gain Control (AGC) for consistent program levels
• "Invisible" compression characteristics assure tighter dynamics and virtually transparent performance
• Instantaneous peak limiting for effective system protection (user defeatable)
• Adaptive control circuits make for fast, simple set-up and no readjustment for varying program dynamics

The Model 320A is almost identical to its predecessor, with the primary improvement being the addition of a newly developed (patents pending) Frequency Discriminate Leveler (FDL) circuit. Lab tests and exhaustive research led to the discovery that, under conditions of program leveling, the human ear perceives the onset of low frequency (bass & percussion) transients differently from transients at higher frequencies. This perception, as it turns out, is a direct function of the relative attack time of the leveler. Without FDL, there is a significantly greater chance that low frequency transients can create an audible "bass pull back" effect. In addition to a potential loss of bass and/or low end "punch", mid and high frequency processing can be negatively impacted. To the listener, the effect can be heard as a perceived loss of bass or even "pumping" at the mid and treble frequency ranges.

FDL eliminates this problem by allowing low frequency transients to trigger a slower attack time on the initial transient. High frequency leveling is still controlled within the attack time determined by the onboard computer. From the listener's standpoint, the benefits are:

• No more bass pullback effect
• More bass punch for better music mixes
• Fast leveling can be used in more applications
• Reduced audio distortion in the leveling mode

There are three main detector circuits for Leveling, Compression and Peak Limiting:

Leveling is performed in a manner related to the way the ear perceives loudness over long time intervals. The circuit effectively maintains output level within 1dB for a 20dB input level change. This action is slow enough to have a minimal impact on program transients or short term dynamics. The addition of FDL further improves the ability of the Leveler circuit to operate smoothly and undetected by introducing a measure of control over the different dynamic characteristics of low frequency vs. high frequency program material. By allowing the Leveler to discriminate between high and low frequency dynamics, the attack time applied to low frequency program is proportionately slower than at higher frequencies. The result is the virtual elimination of "bass pull back" or "pumping" at mid and high frequencies, a condition that is sometimes caused when bass or low pitched percussion dynamics impact the attack characteristics of mid and high frequency program.

When leveling and compression are used together, the Leveler maintains the gain platform so that compression is consistent over the varying levels of program material, providing smooth sounding dynamic compression.

The leveling action is interactive between the two channels when the Leveling Link button is depressed. In this mode, one control signal preserves overall balance and stereo imaging.

Compression is accomplished with a variable ratio, attack and release. The ratio changes depending on program content from 1.1:1 to 3:1. The attack and release times are derived from and vary with program material. The "soft knee" threshold helps to prevent the "choked" sound character often associated with deep compression. Additional program dependent characteristics are imparted by other sections of the Compellor's on-board computers, the Dynamic Verification Gate (DVG), and the Dynamic Recovery Computer (DRC).

The Peak Limiter provides further dynamic control, capable of holding an absolute ceiling of 12 dB above the nominal O VU level. It may be bypassed using a switch located on the front panel. It is recommended that the limiter be bypassed when using the Compellor with a precision multiband limiter such as the Aphex Dominator.

The Silence Gate detects significant gaps in the program material and freezes the processing, thus preventing noise "swell" or "build-up", a condition commonly audible in other automatic gain control devices. The Silence Gate immediately releases when the program resumes.

The Stereo Enhance feature does exactly as the name implies. When stereo information is detected the gain of each VCA is slightly modulated equally. The effect is a subtle natural widening of the stereo image. There is no matrixing of the audio and the effect is completely mono compatible. It has no effect on mono/center material.