API 550B Discrete 4 Band EQ

£1,199.00 (including VAT @ 20%)

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Item available to order

This item is available to order, and we do not currently have the item in stock.

When you place your order, we will request the item from our supplier as soon as possible. We will dispatch this product to you as soon as it is received from our supplier.

"Estimated delivery to you" is our estimate of when we will be able to deliver the product to you, based on our supplier's normal delivery timescales. If we become aware it is going to take significantly longer than normal to deliver this item, we will let you know, otherwise, we will advise by email or text message when the item has been dispatched from our distribution centre.

Estimated delivery to you: 2nd November 2016
FREE Delivery available.

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30 day money back guarantee included

30 day money back guarantee included

Once the product is delivered, you have 30 days to decide that you definitely want to keep it. If you decide it is not suitable for any reason, you can return it back to us for replacement or full refund, including standard delivery charges.

All Products are new unless stated, and include a minimum of one year warranty.

Some items are only eligible for money back guarantee if they are returned to us unused and sealed in the original packaging, and in the case of software, unregistered. These items include:

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We are unable to accept returns of any custom made items designed to work together as a unique package, such as computer system built to a customer’s personal specifications. Exceptions may only be possible with prior agreement of the vendor, and may be subject to a cancellation fee.

Optional: 3 year warranty: £59.95
(Includes 60 day money back guarantee)


The product price includes a one year warranty and 30 day money back guarantee.

However, the Gear4music extended warranty scheme provides an enhanced service, and is designed to offer a higher level of protection than many 'free' warranties offered by some retailers and manufacturers.

The highlights of this enhanced warranty service are:

  • Warranty is extended to 3 years from the date of delivery.
  • Our Money Back guarantee is extended from 30 days to 60 days (terms apply after 30 days)
  • Collection and delivery costs are included for the first two years
  • Claim 50% cash back on the cost of the policy after 3 years if it has not been used!
  • Warranty is transferable if the item is re-sold
  • Loan or replacement equipment will be provided if the product isn't repaired within 30 days
  • If an item can not be repaired, a similar alternative product or cash discount (as defined in this policy) will be offered
  • The policy can be cancelled within 30 days, and at any time after that for a pro-rata discount

Please note that this extended warranty is currently only available on products sold within the EU or EEA, and is subject to the terms and conditions as detailed on the extended warranty certificate provided.

For customers in outlying areas of the country, the price of the Extended Warranty may be marginally higher, due to the potential for higher collection and redelivery transport costs.

This enhanced warranty is in addition to the standard Gear4music and manufacturer warranty policies, and the Gear4music terms and conditions of trade. No statement or condition of sale contained within these terms affects or restricts your statutory rights as defined under the Consumer Contracts Regulation 2014.

Product Ref: 61726

  • Based On API's Original 550 Model
  • API 2530 Op-Amplifier
  • 4 EQ Bands
  • ''Proportional Q'' Design
  • Ideal For Console Use

API 550B Discrete 4 Band EQ

The API 550b Discrete 4 Band EQ is based on API's original 550 model from the late 60's. The 550b follows on from its parent model introducing an additional filter band and several new frequencies. Inside the 550b is API's exclusive circuitry and components, such as the API 2520 Op-Amplifier for high quality sound production. The four EQ bands offer seven switchable filter frequencies that span over four-to-five octaves, hand picked from some of the industry's most revered engineers. The ''Proportional Q'' design is also featured in this unit, widening the filter bandwidth at low settings and narrowing it at higher setting, eliminating the need for additional bandwidth controls. The quality components and long lasting design aspect make this 4 band EQ ideal for console installations.

Product Ref: 61726

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  • 15.9%
  • £41.64
  • £1,499.04
Pay by Finance

To make it as easy as possible for you to get the gear you want, we offer a range of instant finance options. If you spend £250 or more online, you can choose to pay over 48, 36 or 24 months. The majority of decisions are given instantly, so you could get your new gear sooner than you thought!

Representative Example

To help you understand how our finance options work, the examples below are based on a total order value of £250:

Finance APR Deposit to Pay Payments Total Payable
Classic Credit 48 Months 14.9% 14.9% No Deposit 48 months: £6.83
Final payment: £6.83
No settlement fee
Classic Credit 36 Months 15.9% 15.9% No Deposit 36 months: £8.65
Final payment: £8.65
No settlement fee
Classic Credit 24 Months 18.9% 18.9% No Deposit 24 months: £12.41
Final payment: £12.41
No settlement fee

How to Apply

Applying for finance couldn't be easier - if your order totals £250 or more, simply proceed through the checkout as normal, then select Pay by Finance on the payment page, then click the orange APPLY FOR INSTANT FINANCE button. This will start your application with V12 Retail Finance, our finance partner, and completing this form should take approximately 10 minutes.

You should get an instant answer on whether your application has been successful, though in some rare cases V12 may need to look at the application in more detail.

Please note: This is only available on orders placed via the website and is not available in store or via phone currently.

Full Description

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''Proportional Q'' Control

Saul Walker (The founder of API) designed the ''Proportional Q'' control in the '60s, allowing for the widening of the filter bandwidth at minimal settings whilst narrowing it at higher settings, without the need for additional bandwidth controls. This feature helps to minimise the phase-shift sound found in many equalizer units.

Based On The Classic 550

The 550b is based on the API's original 550 developed in the late '60's. The original 550 played a pivotal role in the history of music recording, being a prominent fixture in many recording studios. The API 550b is an updated version of the classic EQ, with an additional filter band and several new frequencies, hand-picked by the industry's finest sound engineers.

The API 500 Series

The API 500 Series focuses on high sound quality and longevity at an affordable price range. Considering most studio rigs undergo a large amount of swapping and changing between equipment, the API 500 series is designed to last, from its high quality components down to its rugged and durable design.


  • 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


  • Numbers Of Bands: 4
  • 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
  • Noise: Actual, unw noise, Distortion: .07 max, @ +18 dBu Output
  • Connectors: 15 position .156sp edge connector