API 527 500 Series Compressor

Discrete 500 Series compressor with classic API features like continuously variable controls and all new options for feed-forward or feed-back compression hard and soft knee shapes and API’s patented THRUST switch
MFR# 527
API 527 500 Series Compressor
API 527 500 Series Compressor video


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Please note: This item requires a 500 Series Rack for operation. Shop racks.

The API 527 500 Series Compressor offers unrivaled versatility and unbeatable tone. With classic API features like continuously variable controls and all new options for feed-forward or feed-back compression, hard and soft knee shapes and API’s patented THRUST switch, there’s nothing the 527 Compressor/Limiter can’t do.


Imagine if you could cram the clean, fast and neutral sonic characteristics of the legendary API 2500 Stereo Bus Compressor into your 500 Series rack module. Well, with the API 527 Compressor/Limiter, you can! Choose between API’s original "feed back" compression algorithm for a slower, more musical form of compression, or the new "feed forward" algorithm for modern VCA-style compression.

Engage API’s classic "over-easy" mode for natural sounding compression, or use the hard knee setting for a more severe limiting effect—perfect for taming transients or parallel compression. Engage the patented THRUST function to apply a high-pass filter before the detector circuit and keep unruly bass frequencies from pegging the needle.

Dial in the perfect tone using the intuitive dual‑concentric attack and release knob. Quickly select release time constants from 0.3 sec to 3 sec using the inner concentric knob, or select attack time constants from 1 millisecond to 25 milliseconds using the outer concentric knob.

Add the signature API sound to any signal just by running it through the iconic 2510 and 2520 discrete op amps—no gain reduction needed!


When Saul Walker started API in 1968, one of his first inventions was the 2520 op amp, which has been an integral part to API’s legendary bright, punchy and clear sound. The 527 Compressor/Limiter draws from a nearly 50 year legacy of innovative designs, combining components from the 225L and the 2500 Stereo Bus Compressor into a compact 500 series Lunchbox module. API connoisseurs will note a remarkable difference between the 527 Compressor/Limiter and API’s other 500 series Lunchbox compressor, the 525. The API 525 compressor features standard peak‑detecting feedback design, while the 527 Compressor/Limiter utilizes modern RMS detection and can be configured for either feed-back or feed-forward modes.


Additional Information

Condition New
Channels Single-Channel
Chassis Module
Module Type 500 Series
Module Slot Count 1 Slot
Digital I/O No

Just bought a pair of 527s for our 1608. Ryan at VK was super helpful, took the time to explain the 527s and how they could be linked in the 1608. Also offered up several other compression options that we should keep on our bucket list. Installation in the 1608 was straight forward and a little bit of soldering allowed us to link the two units for stereo link mode. Drum buss is punchy

By Willis Sound on March 14, 2017

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