API Audio THE BOX - Manual (Page 21)

API “The BOX” Operator’s Manual
21
2.4 550A Equalizer – 500 Slot
Input channels 1 & 2 provide semi-parametric equalization using the legendary API
550A EQ. Input channels 3 & 4 provide two (2) 500 slots for modules that conform to
the standards set forth by the API VRP Alliance. This combination provides the classic
API sound as well as giving the owner modest means to customize their console with a
very wide range of other API and third party products
2.4.1 550A Discrete 3-Band Equalizer
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 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 amounts are selected by three dual-concentric switches, and a push-button
"IN" switch allows the EQ to be silently introduced to the signal path. A small push-
button is used to insert the band-pass filter into the 550A.
The API 550A Equalizer provides three (3) bands of
equalization and a band-pass filter. It has been slightly
repackaged for installation on input channels 1-2. Other than
the repositioning of some controls these equalizers are
identical to other 550A EQs.
Features
•
Three (3) bands of classic API equalization
•
Each band offers 7 API selected center frequencies
•
Reciprocal and repeatable filtering
•
Maximum 12dB of boost/cut per band
•
HF and LF bands 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 renowned 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 its way into many
custom console designs by Frank DeMedio and other leading
engineers. Many of these consoles are still in use today.
Over 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.