The Portico 543 from Rupert Neve is a 500 Series module that delivers unobtrusive, musical-sounding dynamic control and brick-wall limiting. Based on the company's Portico 5043, the 543 provides full control over the standard compressor-limiter functions and includes Feed-Forward/Feed-Back modes, Peak/RMS detection and a built-in side chain High-Pass Filter. Additionally, two units can be linked for stereo operation.
Built around Rupert Neve's custom transformer designs, the 543 can also be used with the compressor inactive to provide a transformer-coupled, high-performance line amplifier. The unit utilizes a VCA (Voltage Controlled Amplifier) to control gain and there is much discussion about whether these types of circuits affect the audio signal. To avoid any such scenario, the 543 makes use of an accurate, low-noise, low-distortion VCA that has essentially no sonic signature of its own.
The compressor also has the ability to switch between Feed-Back and Feed-Forward modes. A feed-back compressor splits the input after it has passed the VCA section and sends the split DC signal back to the VCA for compressor control. In a feed-forward design, the input itself is used prior to being passed through the VCA. One delivers a slightly slower but smoother attack, while feed-forward offers faster, more technically accurate response times. Although the differences are relatively small, they are nonetheless sonically perceptible.
The Peak/RMS mode allows for switching the VCA to respond to either RMS (Root Mean Square) or peak levels. An RMS circuit tends to better mimic the way human ears perceive apparent loudness, while a peak circuit tend to directly respond to the waveform voltage, and is more appropriate for the prevention of clipping and maximizing levels. In this unit, the Peak mode is a Peak/RMS hybrid that incorporates the best of each method.
- Single-channel, transformer-coupled compressor housed in a 500 Series module
- A gain range of -6 dB to +20 dB allows for compensating for any signal loss due to compression
- When the Peak switch is engaged, the compressor uses a combination of peak and RMS (average) detection to determine level - when disengaged, it follows RMS levels
- A switchable 250 Hz High-Pass Filter can be applied to the VCA side chain signal, allowing the compressor circuit to disregard sustained low-frequency content
- With the Link switch engaged on two 543 modules and controls set approximately to the same values, Gain reduction on both channels will be the same, preserving stereo balance and position - function is available either on "link-buss" enabled 500 Series racks, or by hard-wiring the two "link-busses" in non-compatible racks
- When the Link switch is engaged on two connected 543 modules, ducking of one source is possible
- Two peak LED meters display output level and gain reduction