API 550A - 50th Anniversary Edition

Discrete 3-band EQ - hand-wired limited edition reproduction of the original Saul Walker design from the early 1970s
API 550A - 50th Anniversary Edition
API 550A - 50th Anniversary Edition API 550A - 50th Anniversary Edition API 550A - 50th Anniversary Edition API 550A - 50th Anniversary Edition
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Please note: This item requires a 500 Series Rack for operation. Shop racks.

The API 550A 50th Anniversary Edition is a near-identical reproduction of the legendary 550A 3-band equalizer designed by Saul Walker in the late 60s. Featuring a stunning limited edition gold faceplate, these hand-wired 500 series modules are only available as part of a limited run of 50 units.


The original 550A equalizer became API’s standard channel module EQ when the company began manufacturing consoles in 1971. Known for its bright, open, punchy sound, the API 550A EQ has been used on countless hit records over the decades.

The API 550A 50th Anniversary Edition 500 series EQ utilizes an exact reproduction of Saul Walker’s original printed circuit board Equipped with API’s incomparable 2520 op-amp and innovative “Proportional Q” circuitry, the 550A 50th Anniversary Edition offers unparalleled sonic quality.


With 21 points of reciprocal equalization divided into three overlapping ranges, the 550A is capable of creating truly unique filter shapes. For added versatility, the high and low-frequency ranges can be used as peak or shelf filters. 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.

These special limited edition units are painstakingly hand assembled and wired, paying homage to the golden era of analog recording. The individually serialized, limited production 50th-anniversary faceplate give each unit a sleek, elegant feel.


  • Hand-wired Limited Edition model with 50th Anniversary Faceplate
  • Reproduction of the legendary 1971 550A
  • 3 bands of classic API equalization
  • 5 selectable frequency centers on each band
  • High and Low bands offer shelf/peak switching
  • "Proportional Q" narrows filter Q at extremes
  • Switchable band pass filter
  • Individually Serialized (1-50)

Additional Information

Condition New
Chassis Module
Module Type 500 Series
Module Slot Count 1 Slot
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