API 550A 50th Anniversary Edition

50th Anniversary Edition reproduction of Saul Walker’s design of the original 550A 3-band EQ. Limited to 50 Units Worldwide.


The API 550A 50th Anniversary Edition is a reproduction of Saul Walker’s original design of the 550A 3-band EQ.

Each of the API 550A 50th Anniversary Edition modules has been assembled and wired by hand, using an exacting reproduction of the original printed circuit board. Only 50 modules are being built and an individual serial number will mark the unit.

The 550A provides up to 12dB of cut/boost for each of the three bands in 2dB increments. The three bands provide 5 frequency bands each with overlapping frequencies. Both Low and High band can be used as peak or shelf modes while a Filter switch activates a bandpass filter.

The 550A Anniversary Edition also includes Saul Walker’s legendary 2520 Op-amp which combined to the proportional Q design, gives the unmistakable API EQ sound.

API 550A 50th Anniversary Edition Main Features:

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)



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