The API 527A Compressor / Limiter is a single-channel 500-series VCA compressor taking its cues from the 225L console dynamic processor and 2500 mixbuss compressor.
The API 527A includes both feed-forward and feedback topologies which are selectable via the New/Old switch. These modes offer a choice between an aggressive, punchy and "modern" sound or a more laid back vintage sound of more typical classic compressors.
The 527A also boasts a Soft/Hard switch that changes the knee for a natural, transparent "over-easy" compression or the harder knee type for more aggressive curve suited for more severe limiting.
The 527 A also includes API's Thrust found in the original 2500 which applies a filter before the RMS detector circuit to minimise the impact of low-frequencies on the compressor and keep a punchy bottom end.
At the heart of the compressor's sound lies the 2510 and 2520 discrete op-amps that deliver the signature API punchy mid-forward sound.
The output control works akin to the Ceiling control on the API 525 Compressor with the output level remaining fairly constant regardless of ratio and threshold controls. This design lets you make adjustments on the fly without noticeable gain changes.
A DC Link function allows for the linking of several units together for stereo or multi-channel applications.