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From Our Research Team:

An EQ Standard, For More Than 40 Years!

The API 550A is a true classic — an EQ that's been embraced since the late 60s, and a standard by which countless EQs have been judged. Here, reissued in 2004 in its original modular form (after a long, highly anticipated wait), the API 550A puts a piece of music history into your 500 Series chassis. It offers 3-bands of simply classic API equalization, with 5 API-chosen frequency centers available on each band. Thanks to the traditional API fully discrete design, you'll enjoy high headroom, lasting quality, and unbelievable sound from the API 550A.

API 550A 500 Series Modular 3-band Equalizer at a Glance:

• A true classic, reintroduced in 2004 by popular demand
  
• Gives you an amazing level of control
  
• Excellent at affecting or reversing tonal modifications
  
• API's 500 Series: Long-term flexibility, lasting value

A true classic, reintroduced in 2004 by popular demand
Few equalizers enjoy the respect and admiration of the coveted API 550A. Designed by the now legendary Saul Walker in the late 60s, the discrete 550A was first used as a modular OEM equalizer. As the industry rapidly embraced the sonic quality of the 550A, it quickly found its way into many custom console designs by Frank DeMedio and other leading engineers. Many of these consoles are still in use today. Forty years later, the 550A remains the standard against which countless EQs are measured, and it has played a major role in the recording industry for decades. Imitated but never duplicated, the 550A became API's standard channel module EQ when the company began manufacturing consoles in 1971. With virtually all existing units spoken for, popular demand for this EQ resulted in API finally resuming production of the API 550A in 2004.

Gives you an amazing level of control
The API 550A provides reciprocal equalization at 21 points in 7 steps of boost to a maximum of 12dB of gain at each point. The fifteen equalization points are divided into three overlapping ranges. The high- and low-frequency ranges are individually selectable as either peaking or shelving, and a band-pass filter may be inserted independently of all other selected equalization settings. Frequency ranges and boost/cut are selected by three dual-concentric switches, and a pushbutton "in" switch allows the EQ to be silently introduced to the signal path. A small toggle switch is used to insert the band-pass filter into the 550A.

API's 500 Series: Long-term flexibility, lasting value
The beauty of the entire API 500 Series is its long-term flexibility and lasting value — especially when you consider that needs change over time. With a range of mounting frame options, the API 550A will be a valuable asset to your ever-changing studio rigs. It's also ruggedly designed with sound you just won't outgrow — crafted to be your sonic partner for year after year after year.

API 550A 500 Series Modular 3-band Equalizer Features:

• 3 bands of classic API equalization
  
• Each band offers 7 API-selected frequency centers
  
• Reciprocal and repeatable filtering
  
• Maximum 12dB of boost/cut per band
  
• EQ Band 1 and 3 offer shelf/peak switching
  
• "Proportional Q" narrows filter Q at extremes
  
• Traditional API fully discrete circuit design
  
• High-headroom +30dB clip level

The API 550A is a benchmark 3-band equalizer for 40+ decades, and is now available again in its original modular form!

Specification Detail Manufacturer Part Number 550A

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