500 Series 4 Band EQ
Based on API's original 550 from the late '60s, the API 550b is a continuation of the EQ that played a major role in the history of music recording, but with an additional filter band and several new frequencies. Incorporating API's exclusive circuitry and proprietary components (such as the legendary API 2520 Op Amp), the 550b artfully blends the past with the present. So many hit records still depend on the unique 550 sound that engineers around the world find it to be an invaluable tool. In fact, the 550b design has been taken from the original blue prints and spec control drawings from the API archives. It is unlike any other EQ you will ever use.
The API 550b is an extension of the EQ that played one of the largest parts in the history of music recording: the original API 550, on which the 550b is based, but with an added filter band and numerous innovative frequencies. The 550b cleverly blends the past with the present by integrating API’s exclusive circuitry and proprietary components (such as the fabled API 2520 Op Amp). So many sound engineers around the world find it an irreplaceable apparatus that many hit records still depend on the 550b’s unique sound. In fact, unlike any other EQ you will ever use, the 550b’s design has been taken from the initial blue prints and spec control drawings from the API archives.
The API 550b delivers exactly the correct number of controls, rather than a colossal assortment of complex features. Each of the four EQ bands offers seven switchable filter frequencies that span four-to-five octaves, overlapping significantly to help in dual roles: as problem solver and sweetening device. An experienced “who’s who” roster of the recording industry’s most technically-gifted engineers purposely selected these frequencies to be musical, rather than numeric.
The API 550b automatically widens the filter bandwidth at minimal settings and tapers it at higher settings without the need for additional bandwidth controls by making use of API’s “Proportional Q”, an innovation designed by Saul Walker in the 60s. “Phase-shift” sound found in many equalisers is diminished by this unique feature. The user can also “undo” past action with meticulous precision because of the 550b’s reciprocal nature.
Permanently working with an EQ will make the advantages of the API 550b all the more obvious. The astonishing headroom made possible with API’s 2520 Op Amp offers foreseeably warm analogue performance, even under stress, if significant tonal rearrangement is required. The 550b is an irreplaceable and professional audio tool with great flexibility, dependability, longevity and uniformity characteristic of all API products.
- Four bands of our famous sounding equalization
- Each band offers seven API selected frequency centers
- Reciprocal and repeatable filtering
- 12 dB of boost/cut per band
- EQ band 1 and 4 offer shelf/peak switching
- "Proportional Q" narrows filter Q at extremes
- Traditional API fully discrete circuit design
- High headroom +30 dB clip level
- Re-issue of 1967 API 550 EQ with an extra band
Number of Bands: Four
Filter Frequency Centers:
Filter Boost/Cut: ±12 dB
Filter Slope: 12 dB per Octave
Input Impedance: 18.5 K +4 in, 7.5 K -2 in
Output Impedance: Less than 75 Ohms
Nominal Levels: -15 to +15 dBu
Clipping Level: +30 dBu @ ±16 V
Frequency Response: +0, -.3, 30 to 20 kHz
Noise: Actual, unw noise, <-98 dBu, 20-20 kHz
Distortion: .07% max, @ +18 dBu Output
Connectors: 15 position .156sp edge connector
Power Consumption: ±12/18 Volts/DC,@ 40 ma.
Dimensions and Weight
Size: 1.5" X 5.25" X 7.5" Deep
Size (Boxed for Shipping): 4.5" X 6.25" X 10"
Actual Weight: 2.02 lbs.
Shipping Weight: 2.43 lbs.