API / 525

This is an API compressor/limiter. It's a ""feedback"" type compressor. The ""CEILING"" control allows for fine-tuning of 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 in the 1970s, is a ""feedback"" type compressor, similar to the 1176 and 660. Compression is performed by setting the input (threshold) and output (gain) controls. In addition, the ""CEILING"" control allows for fine-tuning of the 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 switches provide four types of auto-release modes: 0.1, 0.5, 1.5, and 2.0. The de-esser function inserts an inverse energy curve filter for vocals to reduce sibilance and pop. The 525 is a complete reissue of one of API's most popular products to date. The 525 is perhaps the most ideal solid-state feedback compressor from its inception to the present day, because it uses a dynamic control method, unlike the VCA compressors that are common today. While the output level is increased, the ""CEILING"" control can increase gain reduction, allowing the user to stably manage the sound level. In reproducing this product, we have succeeded in faithfully adhering to the original design drawings and specifications. To maintain a natural sound decay, the release time is determined by detecting high-frequency components rather than low-frequency components. The attack time is fixed, suppressing sharp peaks without causing pumping. Thus, the 525 is a highly effective compressor/limiter for a wide range of applications, from tracking to mixdown. The synergy of the ""Vintage"" dynamics control, the easy-to-use multi-function control set, and the versatile 500 series case allows the 525 to deliver outstanding performance even under the most demanding conditions. In addition, with its hardwired bypass switch, balanced input, and pin output type similar to other 500 series products, the API 525 continues to be cherished as ""the 525 sound"" even after 25 years. Furthermore, it is possible to link multiple 525s to create a multi-channel configuration. The 525 feedback compressor/limiter utilizes API's original 2510 and 2520 operational amplifiers, ensuring the reliability, long lifespan, and consistently stable operation characteristic of API products.