API Audio 550A

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.

API 550A main features include:

• 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.