Originally launched in the 70s, the API 525 is a “feedback” compressor. An input control (threshold) and output control (make-up gain) are provided, along with an additional “Ceiling” fine-tuning function that can increase the gain reduction (lower limit) while simultaneously increasing the output level. to match, so the user can change dynamics “on the fly” without level changes. A compression/limit switch sets the ratio to 2:1 or 20:1. The attack time is as fast as 15u/s. Four automatic release modes are offered via two switches, 0.1s, 0.5s, 1.5s and 2.0s. A De-Ess function inserts an inverse vocal energy curve filter into the detector for effective sibilance/pop reduction. The 525 design was taken from the original blueprints and specification control drawings in the API files.
Release times vary by frequency, with high-frequency/full-bandwidth content released more quickly than lower frequencies for natural envelope tracking. The attack time is fixed, chosen to catch the fastest peaks, without “pumping”. Equally useful as a tracking, mixing, or program compressor/limiter, the 525 utilizes “vintage” dynamic control and an easy-to-use multi-function control suite. The 525 has a hard-wire bypass switch, a balanced input, and a pinout that is the same as all other 500 series modules. Two or more 525s can be connected for multichannel compression.
The API 525 Compressor makes use of the 2510 and 2520 operational amplifiers and exhibits the reliability, long life and uniformity that are characteristics of all API products.
Characteristics
- Exact reissue of the original API 525 from the early 70s;
- Peak detection feedback compressor/limiter;
- Variable threshold and output levels;
- The exclusive “Ceiling” control combines the main functions;
- Analog VU meter for gain reduction monitoring;
- 4 switchable release modes;
- De-ess function;
- Traditional API fully discrete circuit design;
- Active balanced input/output;
- Wire bypass.
Specifications
- Number of channels: 1;
- Controls: Threshold, Output, Release Mode, Ceiling, Release;
- Ratio: 2:1 or 20:1;
- Frequency response: 30Hz–20kHz.