# EQ550b — Classic American EQ

> Classic American EQ emulation plugin with four bands and selectable frequencies. (iPhone/iPad app by RRS, OOO.)

- Source: https://appshunter.io/ios/app/eq550b/id1507176549 (this page in markdown: same URL + `.md`)
- Developer: [RRS, OOO](https://appshunter.io/developer/1486125568)
- Category: Music, Utilities
- Price: Free with in-app purchases
- Rating: 4.80/5 from 13 App Store ratings · 2 written reviews indexed
- Age rating: 4+
- Requires: iOS 10.0 · 19 MB
- Languages: American English
- Released: 2020-04-10
- Data updated: 2026-08-20
- Monetization: free with in-app purchases
- User reviews in markdown: https://appshunter.io/ios/app/eq550b/id1507176549/reviews.md

## What is EQ550b?

EQ550b AUv3 plug-in — comes as time-limited Demo-version for you to try. It gives you 5 minutes of Free play time. (You can reload the EQ550b AUv3 plug-in as many times as you want, thereby you get the Demo period again and again.) Unlimited version of EQ550b AUv3 plug-in comes as In-App Purchase.

Based on Classic American EQ from the late '60s, the EQ550b 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. With a surprisingly wide range of tonal variations, the EQ550b is an invaluable and professional audio tool with great flexibility and excellent sonic ability.

Features:

• Standalone and AUv3 plug-in;
• Precise port of Rack Extensions plug-in;
• Modeled vintage EQ;
• Four bands of classic American equalization;
• Each band offers seven selected frequency centers;
• 15 dB of boost/cut per band;
• EQ band 1 and 4 offer shelf/peak switching;
• Proportional Q narrows filter Q at extremes;
• Stereo (Mono), Mid or Side EQ modes;
• Undo/Redo;
• A/B comparison;
• 2x/4x/8x Upsampling;
• Macro controllers;
• Built-in Gain Match;
• Scalable GUI.

Rather than offer a huge assortment of complex features, the EQ550b 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.

Making use of Proportional Q 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.

The EQ550b extends the features of the original hardware and joins the flexibility of the digital world to the character of the analog processing. Allows you to choose between equalizer modes (Stereo, Mid, Side) and remove analogue saturation from the processing circuit to deliver pure digital sound.

To use EQ550b as a plug-in, you need an AUv3-compatible host app like GarageBand, Auria, AUM, Cubasis and more — EQ550b will appear in the list of Audio Unit extensions for effect plug-ins in the host app.

## Key features

- Modeled vintage EQ
- Four bands of equalization
- Selectable frequency centers
- Proportional Q filter
- Stereo, Mid, or Side EQ modes
- AUv3 plugin compatibility

## Pricing and in-app purchases

Base price: Free.

**One-time purchases**

| Purchase | Price | Type |
| --- | --- | --- |
| RRS EQ550b Unlimited | $4.99 | one-time |


## Recent user reviews (2 of 2)

All indexed reviews: https://appshunter.io/ios/app/eq550b/id1507176549/reviews.md

### 5/5 — 3D Sound

*2023-01-06*

Don’t really know why this plugin company isn’t more popular than it is. The plugins sound excellent! I’m using them in GarageBand iOS. I bought several and do not regret it at all. They are true to the hardware they are emulating, and they have a very 3D/expensive quality to them in terms of sound. 5 stars!

### 5/5 — Great EQ

*2022-10-14*

All RSS apps are awesome! These guys kill it with every app they make. IMHO they are underpriced. Sound great, easy to use, get them all! New synth kicks!

## Frequently asked questions about EQ550b

### How does the EQ550b demo version work?

The EQ550b comes as a time-limited demo version, offering 5 minutes of free play time. You can reload the plugin as many times as you want to re-access the demo period.

### What is the price of the unlimited EQ550b version?

The unlimited version of the EQ550b AUv3 plugin is available as an In-App Purchase. The base app is free to download and try.

### What devices is EQ550b compatible with?

EQ550b is supported on iPhone, iPad, and iPod. It requires an AUv3-compatible host app to function as a plugin.

### How often is EQ550b updated?

The latest version of EQ550b is 3.0.3, last updated on January 2, 2026. This indicates a commitment to ongoing development and improvements.

### What is the age rating for EQ550b?

EQ550b has an age rating of 4+, making it suitable for a wide range of users. The app's focus is on audio processing rather than content unsuitable for younger audiences.

### What makes EQ550b's Proportional Q feature unique?

Proportional Q narrows the filter's bandwidth at higher boost/cut settings and widens it at minimal settings. This unique feature helps minimize the phase-shift sound often found in other equalizers.

### Can EQ550b be used with other music apps?

Yes, EQ550b can be used as an AUv3 plugin with compatible host apps such as GarageBand, Auria, AUM, and Cubasis. It will appear in the list of available audio unit extensions.

### What are the EQ modes available in EQ550b?

EQ550b offers Stereo (Mono), Mid, or Side EQ modes, allowing for flexible audio manipulation and targeted equalization of different parts of the stereo image.

## Version history (last 5 releases)

### 3.0.3 — 2026-01-02

- Fixed parameters Automation bug.

If you like EQ550b plug-in, please support us by rating this app in the App Store!

### 3.0.2 — 2025-12-27

- Fixed inconsistent Routings switching bug.

If you like EQ550b plug-in, please support us by rating this app in the App Store!

### 3.0.1 — 2025-11-28

- Fixed plug-in startup crash in legacy iOS.

### 3.0.0 — 2025-11-16

- Implemented Gain Matching (GM) feature;
- Implemented Macro-Controllers feature;
- Implemented serial Groups chain feature;
- Implemented User Presets feature;
- Implemented SIMD optimization (experimental);
- Minor bug fixes and improvements.

### 2.5.0 — 2022-11-27

- Implemented Saturation adjust knob;
- Implemented Old/New Saturation mode switch;
- Implemented HQ-mode;
- Implemented GUI Scale on Pinch feature;
- Implemented Presets Drop-down Menu;
- Fixed parameters tweaking crash bug in some DAWs.

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## More apps by RRS, OOO

- [EQ560](https://appshunter.io/ios/app/eq560/id1486125569)
- [EQ-A](https://appshunter.io/ios/app/eq-a/id1492043981)
- [EQ550](https://appshunter.io/ios/app/eq550/id1507132030)
- [PolyIvoks Filter](https://appshunter.io/ios/app/polyivoks-filter/id1507649629)
- [RRS EQ3](https://appshunter.io/ios/app/rrs-eq3/id1507895144)

All apps by RRS, OOO: https://appshunter.io/developer/1486125568

## Related topics

[eq550b](https://appshunter.io/ios/topics/eq550b)

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-08-20.*