Widgets Magazine


“Hand-Wired, Simple Design Minimizes Phase Shift”

YEAR: Late 1960s

HISTORY: The API 550 EQ was designed by Saul Walker in the late 1960s and was first used in API and custom console designs. It has been a very influential piece of recording gear and has been used on countless hit records. It is a 500 series module, which means it needs a 500 series enclosure or “lunchbox,” or needs to be installed in a console that uses 500 series modules. It has a unique sound due to the custom Saul Walker-designed 2520 op amps and the “Proportional-Q” circuitry, which automatically adjusts the bandwidth based on the amount of EQ applied.  This innovative feature eliminated the need for a bandwidth adjustment and also minimized phase shift. Phase coherence is especially important in recording very tight, low end in instruments such as bass guitars and kick drums and this is where the 550 shines. Many recording engineers swear by the vintage 550s due to the hand-wired, simple design and more direct signal path. 

HOW IT’S USED: The API 550 is commonly used in both tracking and mixing of guitars (listen to the guitars on the White Stripes’ “Icky Thump,” engineered by Joe Chiccarelli), vocals and drums.

MODERN EQUIVALENT: API makes excellent modern versions of the 550 – the 550A and 550B EQs. Waves also makes an API 550 plug-in for computer-based recording.

ABOUT THE AUTHOR: Terri Winston is the Founder and Executive Director of Women’s Audio Mission, a San Francisco based non-profit dedicated to the advancement of women in music production and the recording arts. Winston established WAM in 2003 during her tenure as a professor and Director of the Sound Recording Arts Program at City College of San Francisco.

Today, WAM seeks to “change the face of sound” by providing hands-on training at their San Francisco studio, experience, career counseling and job placement to women and girls in media technology for music, radio, film, television and the Internet. To join, or for more info, visit www.womensaudiomission.org.

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