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 provides an astonishing degree of flexibility and precision.
What is VCA compression?
Every compressor has a gain control element in its circuit, and this is generally what determines the “sound” of the compressor. Some compressors use tubes, some use FETs, some use light-dependent resistors, some use a diode bridge – but in the 543, a VCA (Voltage Controlled Amplifier / Attenuator) is used to control the signal’s gain.
In contrast to a diode bridge design like our 535 compressor, which adds a thick, very colorful tonality to the source, the 543 makes use of a very accurate, low noise, low distortion VCA. This provides an immense amount of dynamic control and subtle warmth, without necessarily leaving a heavy sonic imprint on your tracks or mixes.
Feed-Forward or Feed-Back?
This switch changes the point in the signal path where the VCA control voltage is picked off: either before the VCA (feed-forward) or after the VCA (feed-back).
In most of Mr. Neve’s earliest designs, feed-back detection was intrinsic to the musical dynamic response. However, the very nature of a feedback compressor limits the attack time of the compression circuit, as the control voltage has already passed through the VCA itself. To offer faster, more technically accurate response times, feed-forward detection was also implemented in the 543: with the FF / FB switch, both classic and modern VCA responses are available.
RMS or Peak?
Another highly useful features of the 543 is the Peak / RMS mode, which allows the VCA 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.