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API 550b 500 Series 4-band Equalizer , $1,295.00 - Add to Cart Skip to Product Information

API 550b 500 Series 4-band Equalizer

Modular 4-band Equalizer, 500 Series, With 7 API-selected Frequency Centers, 12dB of Boost/Cut Per Band, and Proportional Q Control
API 550b 500 Series 4-band Equalizer
API 550b 500 Series 4-band Equalizer

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API 550b 500 Series 4-band Equalizer
In Stock!

Only 9 left in stock! Order Soon!

This EQ Has Royal API Blood Lines!

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Our Product Research Team

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Incorporating API's legendary circuitry, the API 550b 4-band equalizer exudes that royal API blood line in every ounce of its sonic character. Artfully blending the past with the present, the API 550b carries the torch from the now-classic API 550EQ — delivering just the right amount of controls to solve problems and sweeten the sound. On each of the API 550b's bands, there are seven carefully selected, switchable filter frequencies. It's packed with surprisingly surgical capabilities — but it's all about musicality — you'll find out why top engineers depend on the API 550b everyday. API 550b 500 Series Modular 4-band Equalizer at a Glance:

  • A modern relative of a music-history favorite
  • API's "Proportional-Q" Control
  • Excellent at affecting or reversing tonal modifications
  • API's 500 Series: Long-term flexibility, lasting value

A modern relative of a music-history favorite The API 550 EQ played a major part in the history of music recording in the USA during the 60s and 70s. Originally conceived for use in API's consoles, this latest 550"B" version, the API 550b, is a continuation of the original 1967 550 through the 550A with one 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 blends the past with the present. So many hit records still depend on the unique 550 sound — and you'll find that the 550b will be an invaluable tool you'll turn to again and again. API's "Proportional-Q" Control Making use of "API Proportional-Q", a design introduced by API 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 feature minimizes the "phase-shift" sound found in many equalizers. Excellent at affecting or reversing tonal modifications You'll be surprised by the possibilities the API 550b 4-band equalizer opens up. One of the 550b's most compelling features is its ability to affect or reverse tonal modifications. If major tonal restructuring is required, the extraordinary headroom made possible with API's 2520 op-amp offers predictable and gentle "analog" performance under duress. You've got a surprisingly wide range of tonal variations, just a few knobs away. API's 500 Series: Long-term flexibility, lasting value The beauty of the entire API 500 Series is its long-term flexibility and lasting value — especially when you consider that needs change over time. With a range of mounting frame options, the API 550b will be a valuable asset to your ever-changing studio rigs. It's also ruggedly designed with sound you just won't outgrow — crafted to be your sonic partner for year after year. API 550b 500 Series Modular 4-band Equalizer Features:

  • 4 bands of their famous-sounding equalization
  • Each band offers 7 API-selected frequency centers
  • Reciprocal and repeatable filtering
  • 12dB 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 +30dB clip level
  • Reissue of 1967 API 550 EQ with an extra band

API 550B 500 Series Modular 4-band Equalizer Specifications:

  • Modular 4-band Equalizer
  • Filter Type:"Low" and "High" bands are Peak/Shelf switchable. Low-Mid and Mid-High are peaking type
  • Low Filter Frequency Center: 30, 40, 50, 100, 200, 300, 400Hz
  • Low-Mid Filter Frequency Center: 75, 150, 180, 240, 500, 700, 1Khz
  • Mid-High Filter Frequency Center: 800, 1.5K, 3K, 5K, 8K, 10K, 12.5K
  • High Filter Frequency Center: 2.5K, 5K, 7K, 10K, 12.5K, 15K, 20K
  • Filter Boost/Cut: +/- 12dB
  • Filter Slope: 12dB 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 at +/-16 V
  • Frequency Response:+0, -.3, 30 to 20 kHz
  • Noise:Actual, unw noise, <-98 dBu, 20-20 kHz
  • Distortion:.07% max, at +18 dBu Output
  • Connectors:15 position .156sp edge connector
  • Size: 1.5" X 5.25" X 6" Deep
  • Weight: 2.5 lbs

The API 550b 4-band equalizer artfully blends classic API sound with modern features!

Warranty Info

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Offer applies only to single-receipt qualifying purchases. Select manufacturers may require that only the manufacturer’s products qualify towards the minimum purchase amount needed to be eligible for promotional financing. Otherwise, an invoice that meets the minimum purchase amount and contains at least one qualifying manufacturer product is eligible for promotional financing. No interest will be charged on promo purchase balance, and equal monthly payments are required on promo purchase until it is paid in full. The payments equal the amount financed divided by the number of months in the promo period, rounded up to the next whole dollar. These payments may be higher than the payments that would be required if this purchase was a non-promo purchase. During the last month(s) of the promo period the required monthly payment may be reduced due to the prior months’ rounding. Regular account terms apply to non-promo purchases. New Accounts as of 07/31/2025: Purchase APR is 34.99%. Penalty APR is 39.99%. Min Interest Charge is $2. Existing cardholders: See your credit card agreement terms. Subject to credit approval.

Offer applies only to single-receipt qualifying purchases. No interest will be charged on the promo balance if you pay it off, in full, within the promo period. If you do not, interest will be charged on the promo balance from the purchase date. The required minimum monthly payments may or may not pay off the promo balance before the end of the promo period, depending on purchase amount, promo length and payment allocation. Regular account terms apply to non-promo purchases and, after promo period ends, to the promo balance. New Accounts as of 07/31/2025: Purchase APR is 34.99%. Penalty APR is 39.99%. Min Interest Charge is $2. Existing cardholders: See your credit card agreement terms. Subject to credit approval.

The estimated required monthly payment shown which excludes taxes and delivery equals the amount financed divided by the number of months in the promo period, rounded up to the next cent. During the last month(s) of the promo period the required monthly payment may be reduced due to this rounding. These payments apply only with the financing offer shown. If you make these payments by the due date each month, you should pay off this amount financed within the promo period, if it is the only balance you are paying off. If you have other balances on your account, this payment will be added to any other minimum monthly payments.

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