API 529 Stereo Compressor – 500 Series

The API 529 Stereo Compressor brings the unmistakable punch, clarity, and musicality of API’s legendary compression circuits to the compact and convenient 500 Series format. Drawing inspiration from the acclaimed API 2500, the 529 is designed to deliver everything from subtle dynamic control to bold, aggressive compression — all with the analog warmth and precision that API is known for.

Featuring continuously variable detented controls for Gain, Threshold, Attack, Ratio, and Release, the 529 offers precise and repeatable settings tailored for both tracking and mix bus duties. Whether you’re fine-tuning vocals, tightening drums, or gluing an entire stereo mix, the 529 delivers professional-grade compression with full flexibility.

A standout feature of the 529 is the patented THRUST® circuit, which provides frequency-dependent sidechain processing that preserves low-end impact — perfect for maintaining bass clarity under heavy compression. The unit also includes a selectable Knee control</strong (Soft, Medium, Hard) for shaping the compression curve and a New/Old switch to toggle between modern feed-forward and vintage-style feed-back compression topologies.

Visual monitoring is handled by dual 10-segment LED meters that can display gain reduction or switchable input/output levels, along with an Over Threshold LED for precise visual feedback. The 529 also features auto or manual makeup gain and a comprehensive three-way In/Out switch, including a hard relay bypass for true signal integrity.

At its core, the API 529 is powered by discrete 2520 and 2510 op amps and features transformer-balanced outputs, delivering the iconic analog tone engineers have trusted for decades.

Key Features:

Stereo compressor in 500 Series format
Based on the legendary API 2500 compressor
Continuously variable detented controls: Gain, Threshold, Attack, Ratio, Release
Patented THRUST® circuit for punchy low-end clarity
Three selectable Knee settings: Soft, Medium, Hard
Selectable “New” (feed-forward) or “Old” (feed-back) compression styles
Manual or automatic makeup gain modes
10-segment LED meters for gain reduction and switchable input/output level
Over Threshold LED for precise monitoring
Three-way In/Out switch with hard relay bypass
API 2520 and 2510 discrete op amps with transformer-balanced output

The API 529 offers world-class stereo compression in a portable, rack-friendly package. Perfect for engineers who want the classic API sound on the mix bus, drum groups, or stereo sources — all with the flexibility and control of modern analog design.