The Rupert Neve Designs Portico 543 Mono Compressor delivers unobtrusive, musical-sounding dynamic control and brick-wall limiting found in the Portico 5043 module to the 500 series format. The 543 features a fully controllable compressor-limiter with feed-forward/feed-back modes, Peak/RMS detection and a built-in sidechain high-pass filter. With an unrivaled heritage and a tremendous feature set, the 543 yields a combination of rich warmth, flexibility and precision that is sure to resonate in the ears of sound engineers the world over. Built around Mr. Rupert Neveâ€s custom transformer designs, each 543 module encompasses individually controllable threshold, attack, release, makeup gain, ratio, sidechain HPF, Feed-forward/Feed-back selection and Peak/RMS detection modes. With the compressor inactive, the 543 may be used as a transformer-coupled, high-performance line amplifier. Two 543s may be linked for stereo operation. The chassis is built to standard 500 series specifications, with power and I/O provided by the rack. One of the more unique features of the 543 is the new Peak/RMS mode also found in the Portico II Channel. This switch allows the VCA (voltage control amplifier) to respond to both RMS (Root Mean Square) and peak levels. RMS circuits are considered to better mimic the way the ears perceive apparent loudness, while peak circuits tend to directly respond to the waveform voltage, which may be more of a concern for prevention of clipping and maximizing levels. In this case, peak mode uses a combination of both methods to get the best of both worlds, and avoids the drawbacks of each method on its own.