Based on API’s original 550 from the late ’60s, the API 550b adds an additional filter band and several new frequencies. Incorporating API’s signature 2520 op-amp and Proportional Q, the 550b provides four EQ bands that are overlapped significantly with each band offering seven switchable filter frequencies that span 4 to 5 octaves.

The 550b intuitively widens the filter bandwidth at minimal settings and narrows it at higher settings without the need for additional bandwidth controls. This unique feature minimizes the “phase-shift” sound found in many equalizers.

• 3 bands of classic API EQ, with 7 selected frequency centres

• Reciprocal and repeatable filtering

• 12 dB of boost/cut per band

• EQ band 1 and 4 offer shelf/peak switching

• High headroom +30 dB clip level