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How the Compressor Works

In order to control gain, a V.C.A. or Voltage Controlled Amplifier (or Attenuator) is used. There are many types of V.C. including the use of tubes, discrete and integrated solid state circuits and naturally non-linear devices, each one having its characteristic behavior that reflects sonically on the final performance, and gives it a character or signature that can be musically attractive or not! The 543 makes use of a very accurate, low noise, low distortion V.C.A. having, essentially, no signature of its own.

A part of the audio signal is rectified and smoothed to produce a suitable control voltage for the V.C.A. which has to respond very quickly and have low distortion. If the response is too fast, low frequency signals will themselves, be gain controlled! If the response is too slow, the signal will overshoot and the first few cycles will not get compressed. The speed and accuracy of the response, known as the “attack”, and the time frame that gain remains under the initial control, known as “release” or “recovery” and plays a large part in the way a compressor sounds.

Feed-Forward or Feed-Back?

The 543 also has the ability to switch between feed-forward and feed-back modes. If the V.C.A. Control voltage is taken from the 543 output, (i.e. after the V.C.A.) it cannot act immediately on the V.C.A. because it has already been modified by settings of the V.C.A. and circuits through which it has passed. This is known as a “Feed-Back” compressor. The two compression characteristics are quite different; there is more “Overshoot” and both the attack and recovery ramps are changed, providing the user with powerful choices.

In most of Mr. Rupert Neve earliest designs, feed-back detection controlling the VCA with a rectified voltage from the unit output was intrinsic to the musical dynamic response. However, the very nature of a feedback compressor limits the attack time of the compression circuit. To offer faster, more technically accurate response times, feed-forward detection was implemented on Mr. Rupert Neve’s more modern designs. With the FF / FB switch, both classic and modern VCA responses are available.


Rupert Neve Designs Portico 543 500 Series Compressor

RUPNEVE543
£0.00 £924.00 inc. VAT
£770.00 exc. VAT

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Rupert Neve Designs Portico 543 500 Series Compressor

The 543 Mono Compressor delivers the unobtrusive, musical-sounding dynamic control and brick-wall limiting made famous in the Portico 5043 to the 500 series format. The 543 features a fully controllable compressor-limiter with feed-forward / feedback modes, Peak / RMS detection and a built in side chain 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 Neve’s custom transformer designs, each 543 module encompasses individually controllable threshold, attack, release, makeup gain, ratio, side chain 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, and two 543 may be linked for stereo operation as well. The chassis is built to standard 500 series specifications, with power and I/O provided by the rack.

Specifications
Gain Range
Continuously variable from 6 dB to +20 dB.
Threshold Range
Continuously variable from 36 dB to +22 dB.
Ratio Range
Continuously variable from 1.1:1 to Limit (40:1).
Attack Range
Continuously variable from 20mS to 75mS
Release Range
Continuously variable from 100mS to 2.5 Seconds.
FF/FB
Feed-Forward or Feed-Back VCA control.
Maximum Output Level
Balanced and Floating Transformer Output Maximum output from 20 Hz to 40 kHz is +23 dBu.
Total Harmonic Distortion and Noise
@ 1kHz, +20 dBu output level, no load.
Noise
Measured at Main Output, un-weighted, 22Hz-22kHz, Terminated 40 Ohms. With Gain at Unity, Compressor disengaged Better than 103 dBu. With Gain at Unity, Compressor engaged: Better than 92 dBu
Frequency Response
Main Output, Unity Gain @ 18 Hz, +/- .1dB @ 150 kHz -3 dB.
Crosstalk
Measured Channel to Channel: Better than 90 dB @ 15kHz.
METERS
Monitor INPUT LEVEL and GAIN REDUCTION