API 550A

• 3 bands of classic API equalization
• Each band offers 5 API selected frequency centers
• Reciprocal and repeatable filtering
• maximum 12 dB of boost/cut per band
• EQ Band 1 and 3 offer shelf/peak switching
• "Proportional Q" narrows filter Q at extremes
• Traditional API fully discrete circuit design
• High headroom +30 dB clip level
• Works with API 500 Style racks and consoles

The API 550A Discrete 3 Band EQ module - the return of alegend

Few equalizers enjoy the respect and admiration of the covetedAPI 550A. Designed by the now legendary Saul Walker in the late60's, the discrete 550A was first used as a modular OEMequalizer.

As the industry rapidly embraced the sonic quality of the 550A,it quickly found it's way into many custom console designs by FrankDeMedio and other leading engineers. Many of these consoles arestill in use today.

Forty years later, the 550A remains the standard against whichother EQ's are measured, and it has played a major role in therecording industry for decades.

Still copied but never duplicated, the 550A became API'sstandard channel module EQ when the company began manufacturingconsoles in 1971. With virtually all existing units spoken for,popular demand for this EQ resulted in API finally resumingproduction in 2004.

The 550A provides reciprocal equalization at 15 points in 5steps of boost to a maximum of 12dB of gain at each point. Thefifteen equalization points are divided into three overlappingranges. The high and low frequency ranges are individuallyselectable as either peaking or shelving, and a band-pass filtermay be inserted independently of all other selected equalizationsettings.

Frequency ranges and boost/cut are selected by threedual-concentric switches, and a pushbutton "in" switch allows theEQ to be silently introduced to the signal path. A small toggleswitch is used to insert the band-pass filter into the 550A.

The combination of Walker's incomparable 2520 op amp, and his"Proportional Q" circuitry gives the 550A user an uncomplicated wayto generate acoustically superior equalization.

With the long-awaited reissue of this unit, an EQ that has hadsuch a part in the history of recording is continuing to makehistory in today's music.