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Custom API Audio 550B 500 Series EQ

Brand Name:
Pro-Audio,500 Series,API,
Model Number:

Custom API Audio 550B 500 Series EQ

Min.Order Quantity:
one set
Packaging Details:
Hardshell Case of Custom API Audio 550B 500 Series EQ
Delivery Time:
Within 3days after payment
Payment Terms:
paypal,UnionPay, Visa/MasterCard, Amex, Discover,T/T
Supply Ability:
Contact Now

Product Description

API's 4 Band 500-Series EQ with a slightly cleaner tone and an additional frequency band when compared to the 550A.


Four bands of our famous sounding equalizationEach band offers seven API selected frequency centersReciprocal and repeatable filtering12 dB of boost/cut per bandEQ band 1 and 4 offer shelf/peak switching"Proportional Q" narrows filter Q at extremesTraditional API fully discrete circuit designHigh headroom +30 dB clip levelRe-issue of 1967 API 550 EQ with an extra band

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.

Rather than offer a huge assortment of complex features, the API 550b provides exactly the right number of controls. Its four EQ bands are overlapped significantly to aid in dual roles as problem solver and sweetening device with each band offering seven switchable filter frequencies that span four-to-five octaves. These frequencies, purposely selected to be musical rather than numeric, were selected by an experienced "who's who" list of the industry's most proficient engineers.

Making use of API's "Proportional Q," an innovation designed by Saul Walker in the '60s, the 550b intuitively widens the filter bandwidth at minimal settings and narrows it at higher settings without the need for additional bandwidth controls. This unique feature minimizes the "phase-shift" sound found in many equalizers. In addition, the reciprocal nature of the 550b enables the user to "undo" what has been done previously with exact precision.

The benefits of the API 550b are most obvious to those who work with EQ on a continuous basis. If major tonal restructuring is required, the extraordinary headroom made possible with API's 2520 Op Amp offers the predictable and warm analog performance, even under duress. With a surprisingly wide range of tonal variations, the 500b is an invaluable and professional audio tool with great flexibility and excellent sonic ability.


Number of Bands:


Filter Type:

"Low" and "High" bands are Peak/Shelf switchable.

Low-Mid and Mid-High are peaking type

Filter Frequency Centers:

Low: 30, 40, 50, 100, 200, 300, 400Hz

Low-Mid: 75, 150, 180, 240, 500, 700, 1Khz

Mid-High: 800, 1.5K, 3K, 5K, 8K, 10K, 12.5K

High: 2.5K, 5K, 7K, 10K, 12.5K, 15K, 20K

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


Actual, unw noise, <-98 dBu, 20-20 kHz


.07% max, @ +18 dBu Output


15 position .156sp edge connector

Power Consumption:

±12/18 Volts/DC,@ 40 ma.


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.


Product Specs

Condition:Brand New Make:API Model:API 550B Categories:500 Series, Outboard Gear

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