API 525 Compressor

The API 525 is a classic “feedback” style compressor originally introduced in the 1970s, faithfully recreated from API’s original blueprints and specification control drawings. It features input (threshold) and output (make-up gain) controls, as well as a “Ceiling” function that allows for simultaneous adjustment of threshold and output level.

This makes it easy to apply more compression without affecting overall gain. The unit offers two compression ratios, 2:1 and 20:1, selectable via a compression/limit switch. Attack time is fixed at an ultra-fast 15 microseconds to capture sharp transients, while four selectable release times (0.1s, 0.5s, 1.5s, and 2.0s) provide flexibility for different programme material.

A dedicated De-Ess function engages a filter in the sidechain to reduce sibilance and plosive artefacts effectively. The API 525’s release times vary naturally with frequency, allowing high-frequency content to recover more quickly than lower frequencies, which results in smooth, musical dynamics control without unwanted pumping. Though simple to operate, the API 525’s versatile design makes it equally effective for tracking, mixing, and mastering applications.

The unit includes hard-wire bypass, balanced input, and standard 500 Series pinout compatibility. Multiple API 525s can be linked for stereo or multichannel use. Built with API’s proprietary 2510 and 2520 op-amps, the API 525 delivers the durability, consistency, and sonic quality expected from all API products.

Features

• Exact reissue of API’s original 525 from the early 70’s
• Peak detecting “feedback” compressor/limiter
• Variable Threshold and Output levels
• Unique “Ceiling” control combines key functions
• Analog VU meter for monitoring gain reduction
• 4 Switchable release modes
• De-Ess function
• Active Balanced Input/Output
• Hardwire bypass