Pricing and availability
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Average Price: $1,222
High-end/Boutique
$100
$501+
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High-end
Price History
Based on price data from 4 merchants for "API 550B". Prices shown reflect NEW condition. Tracking began Apr 2, 2026.
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Description
Step into the world of sonic perfection with the API 550B, a 4-band equalizer that marries the timeless charm of classic API sound with the precision needed for modern recording. Building on the legacy of the original 550EQ from 1967, this gem is a nod to the past while embracing the future, featuring an additional band and innovative frequencies that make it a versatile tool for any studio setup. Perfect for engineers who demand more than just functionality, the API 550B's intuitive design offers a seamless workflow. Its "Proportional-Q" circuitry is a standout, automatically adjusting the bandwidth to provide broad strokes for subtle enhancements and surgical precision for more dramatic EQ moves.
The API 550B shines across all instruments, from adding character to vocals to tightening up a drum mix, making it an essential piece for crafting professional soundscapes. Its discrete circuit design ensures the highest fidelity, while the robust build guarantees it will be a reliable fixture in your audio arsenal. Whether you’re a seasoned engineer or a newcomer to the 500-series world, the API 550B is poised to elevate your sound to new heights.
Key Features:
- 4-band equalizer with 7 selectable frequencies per band
- Proprietary "Proportional-Q" circuitry for automatic bandwidth adjustment
- +12dB boost/cut per band with selectable shelf/peak characteristics on bands 1 and 4
- Traditional API fully discrete circuit design
- High-headroom with a +30dB clip level
- Requires API Lunchbox 500-6B or 500 VPR slot rack
- Reissue of the classic 1967 550EQ with an additional band
Product specs
| Number of Channels | 1 |
| High Pass Filter | Yes |
| Low Pass Filter | Yes |
| Number of Bands | 4-band |
| Boost/Cut Range | ±12dB |
| Q Type | Proportional Q |
| Freq Range High | 2.5kHz-20kHz |
| Freq Range Hi-Mid | 830Hz-12.5kHz |
| Freq Range Mid | 75Hz-1kHz |
| Freq Range Low | 30Hz-400Hz |
| Frequency Response | 30Hz-20kHz |
| Depth | 7.5" |
| Weight | 2.02 lbs. |
FAQs
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What is the primary function of the API 550b 500 Series 4-band Equalizer?
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The API 550b is a 4-band equalizer designed for precise tonal shaping. It offers ±12dB boost or cut per band and features proportional Q, making it ideal for enhancing individual tracks, buses, or full mixes with musical transparency.
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How many frequency bands does the API 550b offer and what are their ranges?
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The API 550b provides four frequency bands with ranges as follows: High (2.5kHz-20kHz), Hi-Mid (830Hz-12.5kHz), Mid (75Hz-1kHz), and Low (30Hz-400Hz).
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Can the API 550b be used for both high and low pass filtering?
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Yes, the API 550b includes both high pass and low pass filters, allowing for versatile frequency management in your audio processing.
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What makes the API 550b's EQ unique compared to other equalizers?
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The API 550b features a proportional Q design, which automatically adjusts the bandwidth based on the amount of boost or cut applied, providing a more musical and natural EQ response.
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Is the API 550b suitable for professional studio use?
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Yes, the API 550b is highly regarded in professional studios for its classic sound and precise control, making it a staple for engineers seeking high-quality EQ processing.
Reviews
PROS
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Exceptionally musical, enhancing clarity and richness across all sources
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Provides powerful low end and superior mid-range character
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High build quality with solid aluminum knobs and detented settings for easy recall
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Distinctly improves sound detail, enabling musical surgery on tracks
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Repeatable settings make it easy to use and reliable for consistent sound quality
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Ideal for professional studios and demanding audio environments
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Versatile, excelling in both vocal and instrumental applications
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Outperforms competitors in head-to-head comparisons
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Encourages minimal reliance on software EQing by performing excellently in hardware
CONS
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High price point compared to other EQs in the market
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Knobs can feel stiff, potentially challenging for some users
Owner Insights
We analyzed real musician discussions from forums and Reddit to find what players love, question, and tweak about API 550B.
Features and functionality
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The API 550B provides stepped controls, which some users find advantageous for making quick, decisive EQ adjustments during mixing.
Source
Use cases and applications
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Users frequently apply the API 550B for boosting guitar tracks and enhancing drum overheads, particularly appreciating its broad tonal sculpting capabilities.
Source
Comparisons
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The API 550B is often preferred over the Neve 1073 for guitar tracks due to its frequency ranges aligning well with guitar mixing needs.
Source -
Some users find the API 550B's saturation characteristics beneficial for adding presence to tracks, contrasting it with the more mellow tone of ADM 1540 equalizers.
Source -
Users report the UA plugins closely mimic the hardware's character at low boost levels, but the hardware offers more noticeable distortion and euphoria even without EQ engaged.
Source
User experience
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Owners highlight the API 550B's proportional Q design as being particularly useful for achieving balanced and musical EQ changes without the need for surgical precision.
Source -
A user notes the hardware API 550B has a more pronounced presence, described as "popping out of the speakers" compared to plugin versions.
Source
Software and compatibility
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The Sly-Fi Axis plugin, based on a 550A, includes various modes with different frequency points and a drive function for added color, enhancing its versatility.
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Overloud's 550A and IK Multimedia's API emulations are highlighted as strong alternatives, offering distinct audio characteristics compared to other plugin options.
Source
5.0 out of 5
Based on 1 Review and 8 Ratings
98
Everything you'd expect from API
This EQ rocks, and delivers on almost every source. I shot it out with an API 560, SSL E Series(black), and a RND 551. The 550b won 9/10 times. I'd recommend it every time, and I'm actually about to purchase another for Stereo use.
Artist usage
Add artist
Josh Homme uses the API 550B Discrete 4 Band Equalizer in his studio setup, alongside the API 550A Discrete 3 Band Equalizer. Josh Homme argues that "if you have 48 tracks going through the same gear, it will all have the same tonal quality, so instead we try to mix and match our gear as much as possible."
Listed on the Syro packaging as one of the pieces of gear used on the recording of this album.
Okay, weirdest source yet but- you can see the API's in the rack at 9:44 mark in the attached video. Watch the whole thing for giggles if ya want. Fairly sure thats a pair of ISA 110's as well but I can't say for sure.
In an Instagram story shared on May 4, 2019, Lorn is shown using an API 550B, highlighting its role in his studio setup. The source of this information is a post by DARKLORDCATBUG on Reddit.
"EQ-wise on drums I love API 550A's or B's, doesn't matter, there's a little difference in frequency range… but I love both of these pieces of gear."
Sold on Reverb.com.
From YTG: The 550B is a wonderful 4 channel EQ. I had this in a vocal chain with the Neve, and the Brute Compressor. It is in Excellent condition. I'm selling because I'm doing more EQ-ing in the box.
Posted on the official Astronaut Facebook page captioned, "vocal processing"
According to a list of equipment which is used in his studio, Crowdspacer, Joakim is also a user of API 550B 4-band EQ.
“When I EQ, I’m looking to do something creative rather than just ‘clean up.’ That’s when I go for one of my six go-to EQs: SSL 9080 XL K for its high and low pass filters; Quad 8 or Neve 1073 for the low end; Quad 8 or Motown for lows/low mids; Motown, 1073 and API 550B for mids/high mids; and Avalon 2055 for its silky high end.
We were influenced by albums like Kanye [West’s] The Life Of Pablo, Frank Ocean’s Blonde and all of Drake’s stuff from a sonic point of view. We were really working on getting a high-end vocal sound, which would be great against the darkness of the drums and the bass and it would allow Stormzy’s vocal to really cut through. The main mic we used was a Brauner VM1 into an Avedis preamp, into an API 550 EQ and a Tube Tech CL1B compressor, so it was a pretty high-end chain. We also used the UTA preamp as well, which has its own EQ on different tracks. Then we would take Stormzy’s vocal and bounce it out through the desk and through another compression stage – we’ve got the UTA Fairchild compressor, which is incredible.
Album Usage
The API 550B has been featured on the following albums:
Genre Usage
Based on how artists on Equipboard use this gear, it is most commonly found in the following genres.
Used With
Based on how musicians on Equipboard use API 550B, it is most commonly used with the following gear.
Community setups
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