API 550A Equalizer – Production Model (500 Series)

The API 550A Production Model is a faithful reissue of the iconic 3-band equalizer found in the original API consoles of the 1970s. Designed for the 500 Series “lunchbox” format, the 550A delivers the unmistakable analog tone, precision, and punch that has made API EQs a gold standard in professional recording studios for over five decades.

This production model features three bands of classic API equalization, each offering seven carefully selected frequency centers tailored for musical and effective tonal shaping. With up to ±12 dB of boost or cut per band, the 550A delivers smooth, repeatable, and reciprocal EQ that excels on everything from vocals and instruments to full mixes.

The high and low bands include switchable peak or shelf modes for added flexibility, while API’s proprietary “Proportional Q” circuitry automatically adjusts the bandwidth depending on the amount of gain — ensuring musical results even with extreme EQ moves. Built with fully discrete analog circuitry and powered by the legendary API 2520 op amp, the 550A provides high headroom performance with a clip level of +30 dB.

Key Features:

• 3-band equalizer with API’s signature analog tone
• Each band features 7 API-selected frequency centers
• ±12 dB of reciprocal and repeatable boost/cut per band
• High and low bands offer shelf or peak operation
• Proportional Q design narrows bandwidth at high gain levels
• Fully discrete circuit design with API 2520 op amps
• High headroom performance with +30 dB clip level
• Reissue of the original 550 EQ module from API consoles
• 500 Series format – fits all standard lunchbox and rack enclosures

The API 550A Production Model brings vintage API equalization to modern workflows, offering legendary analog sound, intuitive control, and professional-grade build quality — a must-have EQ for any serious engineer or producer.