API 550A Discrete 3-band Equalizer
API 550Agives you 3 bands of simply classic API equalization, with 7 API-chosen frequency centers available on each band. With the traditional API fully discrete design, you'll enjoy high headroom, lasting quality, and unbelievable sound from the API 550A.
Few equalizers enjoy the respect and admiration of the coveted API 550A. Designed by the now-legendary Saul Walker in the late '60s, 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 its 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 EQs 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 21 points in 7 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.
3 bands of classic API equalization
Each band offers 7 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
Output Impedance: Less than 85Ω (transformer isolated)
Nominal Operating Level: –15 dBm to +12 dBm
Insertion Loss: None (bridging)
Frequency Response, Unequalized: ±0.5 dB 30 Hz to 20 kHz
Noise: Unequalized, output noise of –90 dBm, high level strapping and –98 dBm, low level strapping, 20 Hz to 20 kHz unweighted
Clipping Level (3% THD): +30 dBm
Power Requirement: ±15 volts to ±18 volts @ 70 ma
Connector: 30 pin PC connector supplied
Size: 1.5" x 5.25" x 7.75" Deep
Weight: 2 lbs.
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