API / 525A

The API / 525A is a 500 series discrete FET compressor/limiter.

■Discrete FET compressor/limiter
■500 series

Introduced in the early 1970s and reissued over 20 years ago, the 525 Discrete Compressor has become one of the most trusted vintage-style compressors in the industry. Building on the powerful circuitry of the original 525, the new 525A maintains a discrete audio path while expanding its capabilities to accommodate even more applications in modern studios. A clever combination of API's proprietary transformers and 2510 and 2520 operational amplifiers preserves the sonic characteristics of the original while delivering the reliability, durability, and consistent quality common to API products.


・Attack time can be adjusted from 15 microseconds to 15 milliseconds (new feature)
・7-step release mode selectable (0.05 seconds to 2.0 seconds) (new feature)
・Unique “Ceiling Control” function that adjusts threshold and makeup gain at the same time
-Classic 1970s style analog gain reduction VU meter
・Traditional API discrete output circuit
・Equipped with 2520 and 2510 operational amplifiers
・Unique API output transformer
・Balanced input/output compatible
・Hardware bypass

■Product specifications
Input impedance 80kΩ (balanced)
Output impedance 75Ω (transformer type, balanced)
Maximum input level +27dBu
Maximum output level +28dBu
Attack time 15μsec～15msec
Release time +.05, .1, .2, .3, .5, 1.0, 2.0sec
Slope compression/2:1, limiting/20:1
Maximum gain reduction 25dB
Metering Illuminated analog gain reduction dB meter with gain reduction LED indicator
Frequency response ±.5dB, 20Hz-40kHz
S/N ratio 112dB
Power consumption 3 watts
Dimensions: approx. 3.81cm x approx. 13.34cm x approx. 17.78cm
Weight approx. 0.68kg