API 527A Compressor/Limiter

The API 527A Compressor/Limiter is a versatile dynamics processor built on API’s heritage of VCA-based designs, following in the footsteps of the 225L, 529, and the iconic 2500 series bus compressors. Designed for flexibility and precision, it offers a choice between two compression topologies: classic feedback-style gain reduction (“OLD”) and modern feed-forward compression (“NEW”), allowing engineers to choose the best approach for each application.

A front-panel “SOFT”/“HARD” knee switch enables users to switch between smooth, natural compression and a sharper, more aggressive limiting characteristic. The patented THRUST® circuitry, which protects low frequencies from over-compression by inserting a filter before the RMS detector, can also be engaged via the front panel, preserving punch and clarity in the low end.

The API 527A maintains consistent output levels regardless of threshold or ratio adjustments, similar to the Ceiling control on the API 525, allowing users to make live adjustments without introducing level jumps. For stereo and multichannel work, multiple units can be linked via the DC link function for precise and coherent group compression.

Built with API’s discrete 2510 and 2520 op-amps, the API 527A offers the reliability, long life, and distinctive sonic character expected from API gear, making it an essential tool for tracking, mixing, and broadcast applications.

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