Based on the same circuitry found in the Portico 5045, the Rupert Neve Designs 545 is a 500-series dynamics-taming unit, one which can be used for gating purposes in pro audio scenarios both in the studio and on the stage. It's suitable for use on both vocals and instruments and can help suppress feedback on the stage.
While it shares some similarities with conventional noise gates, the unit operates on its own principle, eschewing filtering or digital processing in favor of custom input and output transformers. These transformers help the unit sense when someone is singing or playing their instruments. When it senses signal, the unit passes signal through, and when it no longer senses signal, it reduces gain appropriately.
The unit has a Threshold control which sets the dBu level at which the process of signal attenuation starts. A Depth control sets the amount of reduction, giving you anywhere from 0 to -20 dB. A Fast switch changes the speed of the attack and release parameters, and a Peak detection button changes the mode of the detection circuit from RMS to Peak modes.
This unit is compatible with any compatible 500-series chassis. It requires such a chassis to operate.
Threshold: This knob sets the dBu level at which the Primary Source Enhancer engages.
Depth: This knob controls the amount of attenuation applied after the input signal falls below the Threshold knob. By rotating the Depth control clockwise from 0 towards -20 dB, the 545 will attenuate the input signal more dramatically, letting you find the perfect balance between audibility and feedback/signal reduction.
Fast: This illuminated push button selects between two time constants that determine how quickly the attenuation occurs in quiet sections. Without this button pressed, the 545 achieves a slower attack and release that is useful as a starting point for most sources. Pressing the Fast push-button engages the faster attack and release time constant, useful on more dynamic sources or passages where faster transient detection is necessary.
Peak: This illuminated push-button selects between RMS and Peak detection modes. When illuminated, the 545 is in peak mode. This is useful for detecting faster transient peaks, and for creative dynamic envelope shaping. When not illuminated, the 545 is in RMS mode, which utilizes a slower, more averaged response characteristic in the sidechain.