API

The 550b is the most famous equalizer in the world. Using the all discrete 2520 op-amp, the 550b provides the most sought after sound in the recording industry.

The 560 is the most famous graphic equalizer in the world. Using the all discrete 2520 op-amp, the newly revised version of the 560 provides ten proportional "Q" slide fader bands.

This often-copied equalizer has become a standard in studios around the world.

The API 215L is a unique passive, sweepable filter, designed specifically to contour the sound in such a way that it sounds natural.

The lineage of the 5500 circuit can be traced back to the original 550 equalizer designed by Saul Walker, the founder of Automated Processes Inc.