# EQ550 — Classic American EQ

> Classic American EQ emulation plugin with Proportional Q for audio production. (iPhone/iPad app by RRS, OOO.)

- Source: https://appshunter.io/ios/app/eq550/id1507132030 (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: 4.50/5 from 11 App Store ratings · 3 written reviews indexed
- Age rating: 4+
- Requires: iOS 10.0 · 20 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/eq550/id1507132030/reviews.md

## What is EQ550?

EQ550 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 EQ550 AUv3 plug-in as many times as you want, thereby you get the Demo period again and again.) Unlimited version of EQ550 AUv3 plug-in comes as In-App Purchase.

The EQ550 faithfully captures the punch, low-frequency transparency, and ultra-tight imaging of iconic American EQs of the late 1960’s.

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.

Features:

• Standalone and AUv3 plug-in;
• 3 bands of classic American equalization;
• Each band offers 7 selected frequency centers;
• Maximum 15dB of boost/cut per band;
• EQ Band 1 and 3 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.

The EQ550 provides reciprocal equalization at 21 points in 5 steps of boost to a maximum of 15dB of gain at each point. The twenty one equalization points are divided into three overlapping ranges. The high and low frequency ranges are individually selectable as either peaking or shelving, and a band-pass filter may be inserted independently of all other selected equalization settings. Frequency ranges and boost/cut are selected by switches, and a pushbutton «IN» switch allows the EQ to be silently introduced to the signal path. A small toggle switch is used to insert the band-pass filter into the EQ550.

The EQ550 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 EQ550 as a plug-in, you need an AUv3-compatible host app like GarageBand, Auria, AUM, Cubasis and more — EQ550 will appear in the list of Audio Unit extensions for effect plug-ins in the host app.

## Key features

- Standalone and AUv3 plugin
- 3 bands of classic American equalization
- Proportional Q filter bandwidth
- Stereo, Mid, or Side EQ modes
- Undo/Redo and A/B comparison
- Scalable GUI

## Pricing and in-app purchases

Base price: Free.

**One-time purchases**

| Purchase | Price | Type |
| --- | --- | --- |
| RRS EQ550 Unlimited | $4.99 | one-time |


## Recent user reviews (3 of 3)

All indexed reviews: https://appshunter.io/ios/app/eq550/id1507132030/reviews.md

### 3/5 — Needs a MacOS release to be realistically usable

*2023-01-28*

Title says it all. I like this as a 550A emulator, especially for the price. Pretty nice features and interface, although I don’t love the curve in the saturation knob. Basically goes from no audible difference to total fuzz in like one notch. Feels like they used a virtual “linear pot” where a log would have been the ticket. I also would like an option to use stepped gain values like on an actual 550. All that said, the sound of this thing is pretty nice.

BUT. The lack of a version for MacOS cripples this plugin. Using more than a few instances on a project quickly overloads my iPad, forcing me to try to port it to my laptop in order to keep moving forwards. Then I find out all my plugins are disabled with no hope of using them. This, imo, is a major oversight and it relegates this from tool to toy status. Yes, I know it’s just GarageBand, but come on.

### 5/5 — Great!

*2022-10-14*

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

### 1/5 — Sounds amazing until..

*2020-05-20*

Loading this breaks my whole garageband session now. There’s just a high pitched click and then everything goes silent. The only way to fix it is to start a new project without loading this eq.. so it’s kinda useless

## Frequently asked questions about EQ550

### How long can I use the EQ550 demo?

The EQ550 offers a time-limited demo version with 5 minutes of free play time. You can repeatedly reload the plugin to access this demo period again.

### What is the full price of EQ550?

The unlimited version of the EQ550 AUv3 plugin is available as an in-app purchase. The specific price for the full version is not detailed in the provided data.

### Does EQ550 have ads?

No, EQ550 does not contain advertisements. The app is free to download and use in its demo mode, with the full functionality unlocked via an in-app purchase.

### What devices is EQ550 compatible with?

EQ550 is supported on iPhone, iPad, and iPod. It requires an AUv3-compatible host app to function as a plugin.

### What is the age rating for EQ550?

EQ550 has an age rating of 4+. This indicates it is suitable for users of all ages, with no mature content concerns.

### How often is EQ550 updated?

The latest version of EQ550 is 3.0.3, last updated on January 2, 2026. This suggests a relatively recent update, though specific update frequency is not detailed.

### What makes EQ550's Proportional Q unique?

The Proportional Q feature intuitively widens filter bandwidth at minimal settings and narrows it at higher settings. This unique characteristic minimizes the 'phase-shift' sound often found in other equalizers.

### Can EQ550 be used without a host app?

Yes, EQ550 can be used as a standalone application. It also functions as an AUv3 plugin within compatible host applications like GarageBand, Auria, AUM, and Cubasis.

## Version history (last 5 releases)

### 3.0.3 — 2026-01-02

- Fixed parameters Automation bug.

If you like EQ550 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 EQ550 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 — 2025-09-26

- 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 GUI Scale on Pinch feature;
- Implemented Presets Drop-down Menu;
- Fixed parameters tweaking crash bug in some DAWs.

## Apps similar to EQ550

| App | Rating | Price | Category |
| --- | --- | --- | --- |
| [Kompresor](https://appshunter.io/ios/app/kompresor/id1572077067) | 5.0 (3) | $24.99 | Music |
| [FabFilter Pro-Q 2](https://appshunter.io/ios/app/fabfilter-pro-q-2/id1401182622) | 4.8 (24) | $29.99 | Music |
| [FabFilter Pro-Q 3](https://appshunter.io/ios/app/fabfilter-pro-q-3/id1469019469) | 4.7 (47) | $29.99 | Music |
| [RTA](https://appshunter.io/ios/app/rta/id298839433) | 4.0 (25) | $4.99 | Music |
| [De-Esser AUv3 Audio Plugin](https://appshunter.io/ios/app/de-esser-auv3-audio-plugin/id1462171273) | 3.4 (19) | $9.99 | Music |
| [RT60](https://appshunter.io/ios/app/rt60/id298840320) | 3.4 (5) | $34.99 | Music |

## More apps by RRS, OOO

- [EQ560](https://appshunter.io/ios/app/eq560/id1486125569)
- [EQ-A](https://appshunter.io/ios/app/eq-a/id1492043981)
- [EQ550b](https://appshunter.io/ios/app/eq550b/id1507176549)
- [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

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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.*