API 550A Saul Walker Edition

The new API 550A Saul Walker Edition is identical in circuit design and parts complement to the recently discontinued re-issue version, with the addition of a special custom face-plate. The unit will also feature the signature of its designer, Mr. Saul Walker, founder of API.


API 550A Saul Walker Edition LTD Edition Features :

• Features a custom faceplate and API founder Saul Walker's signature
• Limited Edition collectable model
• 3 bands of classic API equalization
• Each band offers 5 API-selected frequency centers
• Reciprocal and repeatable filtering
• Maximum 12dB 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 +30dB clip level

Few equalizers enjoy the respect and admiration of the coveted API 550A. Designed by the now legendary Saul Walker in the late 60's, the discrete 550A was first used as a modular OEM equalizer. As the industry rapidly embraced the sonic quality of the 550A, it quickly found it's way into many custom console designs by Frank DeMedio and other leading engineers. Many of these consoles are still in use today.

Forty years later, the 550A remains the standard against which other EQ's are measured, and it has played a major role in the recording industry for decades. Still copied but never duplicated, the 550A became API's standard channel module EQ when the company began manufacturing consoles in 1971. With virtually all existing units spoken for, popular demand for this EQ resulted in API finally resuming production in 2004.

The 550A provides reciprocal equalization at 15 points in 5 steps of boost to a maximum of 12dB of gain at each point. The fifteen equalization points are divided into three overlapping ranges. The high and low frequency ranges are individually selectable as either peaking or shelving, and a band-pass filter may be inserted independently of all other selected equalization settings. Frequency ranges and boost/cut are selected by three dual-concentric switches, and a pushbutton "in" switch allows the EQ to be silently introduced to the signal path. A small toggle switch 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 way to generate acoustically superior equalization.

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

API 550A Specifications :

• Number of Bands: Three
• Low and High bands are Peak/Shelf switchable.
• Filter Frequency Centers:

                   Low: 60, 100, 200, 300, 400Hz
                   Mid: .4, .8, 1.5K, 3K, 5K
                   High: 5K, 7K, 10K, 12.5K, 16K

• Filter Boost/Cut: +/- 12dB
• Filter Slope: 12dB per Octave
• Input Impedance: 18.5K +4 in, 7.5K -2 in
• Output Impedance: Less than 75 Ohms
• Nominal Levels: -15 to +15dBu
• Clipping Level: +30dBu @ +/- 16V
• Frequency Response: +0, -.3, 30 to 20kHz
• Noise: Actual, unweighted noise, <-98 dBu, 20-20kHz
• Distortion: .07% max, @ +18dBu Output
• Connectors: 15 position .156 sp edge connector
• Size: 1.50 X 5.25 X 6 Deep
• Power Consumption: 12/18 Volts/DC,@40 ma.