API 527A 500 Series Compressor/Limiter

The API 527A 500 Series Compressor/Limiter Module Carefully retains the circuit structure and sound of the original 527, and offers the same outstanding performance but adds Improved LED Monitoring of Gain Reduction and a Hard Bypass Option.

The API 527A Compressor/Limiter 500 Series Module takes its place alongside the family of API VCA based compressors, retaining the circuitry of the insanely popular 527 and adding an expanded feature set. The 527A Compressor features “feed forward” (NEW) and “feed-back” (OLD) gain reduction methods selectable on the front panel, providing a choice of “that old way” or “the new way” of compression, for the highest level of flexibility in signal gain control. The “old way” or feed-back method is what most of the classic compressors used for the gain control circuit. The “new way” gain reduction is more typical of the newer VCA type compressors that rely on RMS detectors for the gain control voltage.

There is a “SOFT”/”HARD” knee switch for an “over-easy” type compression resulting in a very natural, uncompressed sound or a typical sharp knee type that lends itself to a much more severe limiting effect.

The patented THRUST ® function can be switched in and out via the front panel as well, applying a filter before the RMS detector circuit that preserves that punchy bottom end. Two or more 527A Compressor/Limiters can be linked together via a DC link allowing multiple units to be combined for stereo and multichannel applications.

The output level remains fairly constant regardless of the threshold or ratio control, much like the “more/less” Ceiling control on the API 525 Compressor. This allows for live adjustments without any noticeable gain changes in the program level.

The 527A Compressor/Limiter makes use of the 2510 and 2520 discrete op-amps and exhibits the reliability, long life, and signature sound which are characteristic of API products.

API 527A Features:

• Feed-forward or feed-back compression
• Hard or soft knee compression
• Patented THRUST ® switch for frequency-dependent sidechain control
• Continuously variable, 31 position detented THRESHOLD control
• Continuously variable, 31 position detented RATIO control
• Continuously variable, 31 position detented ATTACK and RELEASE controls
• Continuously variable, 31 position detented OUT (output) level control
• 10-segment gain reduction/VU meter (GR/Output) Overload LED
• IN switch with soft and hard relay bypass
• Audio circuit uses the 2510 and 2520 discrete op-amps