API 525 500 Series Compressor

Originally introduced in the 1970s, the API 525 is a feedback-type compressor, akin to models like the 1176 and 660. It features threshold and make-up gain controls, with an added "Ceiling" fine-tune function for precise compression adjustments without affecting output levels. A compression/limit switch allows you to select a 2:1 or 20:1 ratio, and it offers a rapid attack time of 15 microseconds. You can choose from four auto-release modes (0.1s, 0.5s, 1.5s, & 2.0s) via two switches. Additionally, a De-Ess function reduces sibilance and p-pops effectively. The API 525 is an identical reissue of one of API's most popular products.

As one of the most successful solid-state feedback compressors in history, the API 525 delivers a unique dynamic control behavior distinct from VCA "feed-forward" compressors commonly used today. Its versatile "ceiling" control allows for dynamic adjustments without affecting levels, making it highly flexible. This reissued design closely follows the original blueprints and specifications from the API archives.

Release times adapt to different frequencies, ensuring a natural envelope tracking with faster release for high-frequency content. The fixed attack time captures peak transients without excessive "pumping." Suitable for tracking, mixdown, or program compression/limiting, the API 525 excels in scenarios where compression is a routine need. Its vintage dynamics control, user-friendly multifunction parameters, and compatibility with various 500 Series setups make it a top choice. The addition of a hard-wire bypass switch, balanced input, and a standardized 500 Series pinout further enhance its appeal. Multiple 525 units can be linked for multi-channel compression.

The API 525 Feedback Compressor/Limiter relies on the 2510 and 2520 op-amps, ensuring the reliability, long life, and consistency that API products are known for.