API / 525

This API compressor/limiter is a ""feedback"" compressor. The ""CEILING"" control allows you to fine-tune the threshold and gain without changing the output.

■Compressor/Limiter
■Input Impedance: >30kΩ (Balanced)
■Output Impedance: <100Ω (Transformer Balanced)
■Operating Level: -15dBu to +20dBu
■Noise: <-98dBu (+10dBu Output @ 10dB Compression)
■Frequency Response: 30-20kHz (±0.5dB)
■Distortion: 0.5% (30-20kHz)
■Maximum Gain Reduction: 25dB
■Attack Time: 15μs
■Release Time: 0.1, 0.5, 2.0, 2.5s
■Compression: 2:1
■Limit: 2:1
■Dimensions: W38×H133×D152mm
■Weight: 800g

The 525, released as early as the 1970s, is a ""feedback"" compressor, similar to the 1176 and 660. Compression is achieved by setting the input (threshold) and output (gain) controls. Additionally, the ""CEILING"" control allows fine adjustment of threshold and gain without changing the output. The compression/limit switch sets the compression ratio to either 2:1 or 20:1. The attack time is 15 μsec or more. Two switch combinations offer four auto-release modes: 0.1, 0.5, 1.5, and 2.0. The de-esser function inserts an inverse energy curve filter into the vocal to reduce sibilance and pops. The 525 is a perfect reproduction of API's most popular product to date. The 525 is perhaps the most ideal solid-state feedback compressor, from its inception to the present day. Unlike today's common VCA compressors, it utilizes a dynamic control method. The ""CEILING"" control allows for increased gain reduction while increasing the output level, allowing users to maintain stable sound levels. This reproduction faithfully follows the original design drawings and specifications. To maintain a natural, lingering sound, the release time is determined by detecting high-frequency content rather than low-frequency content. The fixed attack time suppresses sharp peaks without pumping. This makes the 525 an extremely effective compressor/limiter for a wide range of applications, from tracking to mixdown. The ""vintage"" dynamics controls, easy-to-use multifunction control set, and versatile 500 Series case combine to ensure the 525 delivers outstanding performance under even the most demanding conditions. Additionally, with a hardwired bypass switch, balanced input, and pinouts consistent with other 500 Series models, the API 525 continues to be recognized for its ""525 sound"" even after 25 years of use. Multiple 525s can also be linked for multi-channel operation. The 525 Feedback Compressor/Limiter uses API's original 2510 and 2520 op-amps, providing the reliability, long life, and consistently stable operation that are characteristic of API products.