Taking the legendary API Audio 550 from the '60s and adding an extra band and additional frequencies, the 550b is a 500-series EQ module with four bands of EQ control, ±12 dB of boost/cut per band, and seven selectable frequencies per band. Sporting switchable peak/shelving for the high and low bands, this EQ is versatile and highly musical.
The 550b offers a very high headroom of +30 dB, helping you to avoid clipping when adding gain to frequency bands. With Proportional Q technology, the filter bandwidth narrows at the extremes and widens at the minimal settings, helping to avoid the phase-shifting effect of some EQs. Along with stepped controls for easy recall, the 550b sports a manual EQ in button. With the famed API 2520 op-amp circuitry built in, this EQ module provides predictable and warm EQ performance.
So many hit records still depend on the unique 550 sound that engineers around the world find it to be an invaluable tool. In fact, the 550b design has been taken from the original blueprints and spec control drawings from the API archives.