Updating one of the most influential dynamics processors in music history, the 50th Anniversary Reissue Omnipressor 2830AU from Eventide provides users with flexible operation in a rackmountable unit, capable of deftly flowing from compression and limiting to expansion and gating, all with the turn of a knob. But the Omnipressor 2830AU isn't just versatile, it's also unique, sporting unconventional dynamics functions like the dynamic reversal, the first of its kind, which reverses transient peaks and troughs to produce a simulated tape reversal sound.

The original 1976 Omnipressor was the first processor to introduce the concept of side-chaining, and the reissue is no different, sporting both transformer-balanced XLR and unbalanced 1/4" side-chain I/O, as well as line I/O and link connections for optional stereo processing. The meter sports a three-way switch for selecting between input, output, or gain monitoring. Mix control lets you engage in parallel compression, and you also get a relay-bypass switch, input and output level control, gain, attenuation, threshold control, and much more. And once linked, you can operate in three modes: Stereo Mode for typical stereo dynamics processing, Master Mode for controlling a chain of units with one master unit, and VCA Mode for transforming your Omnipressor into a high-quality voltage-controlled amplifier.

It also introduced the notion of the side-chain and foretold techniques that today we take for granted like lookahead processing. One of its first customers was a young Brian May, lead guitarist of Queen. With the Omnipressor in his rig, his sound was never the same.

By making these envelopes louder than the peaks, the illusion that the sound is coming out backward is generated. Likewise, drum sounds consist of peaks roughly coincident with mechanical impact, followed by a decay envelope. In general. any material with wide dynamic range can be reversed, and by experimenting with forward and reversal playback, you can achieve an incredible array of effects.

• Dynamic Reversal: An input level of +10 dB results in an output of -10 dB, and vice versa.
• Gate: As the signal decreases below +10 dB, the device gain rapidly goes to minimum.
• Expansion: A 40 dB input range results in a 60 dB output range, increasing dynamic range.
• Control Centered: Input level equals output level.
• Limiting: Gain is unity until input is 0 dB. Above 0 dB, a 30 dB change in input produces a 6 dB output change.
• Infinite Compression: Output level remains unchanged regardless of input level.

• Line switch controls the relay-bypass function
• Input and Output level controls
• Mix control for wet/dry adjustment and parallel compression
• Side-chain enables or disabled side-chain audio path
• Input Threshold controls the operating point of the Omnipressor
• Bass cut for reducing low-end leakage into your signals
• Control Attack Time and Release Time
• Three-way switch for Meter Function: Input, Gain, or Output monitoring
• Main Function knob scrolls through basic modes of operation (compression, limiting, reversal, etc.)
• Atten Limit adjusts the limits of maximum attenuation, with a max reduction of 30 dB
• Gain Limit commands the maximum gain of the Omnipressor
• Link activates or deactivates the unit to unit linking function

Connect an Omnipressor and an Eventide Digital Delay Line, or similar delay device. Enable the side-chain input. What you have just fabricated is a compressor that can read the future, or, in more common parlance, one which has a negative attack time. 

Since identical circuitry with identical time constants is used to produce compression and expansion, perfect dynamic tracking is obtained. If compression and expansion ratios are set properly, the system should be transparent to the listener.