# OB vs RX

The clearest difference is in-app purchases: OB at none against RX's 1. OB also leads on chart position (#199 vs unranked). RX's advantage is update cadence (weekly vs every 2 months) and price ($9.99 vs $14.99). On ads, device support and iOS requirement there is nothing between them.

OB costs $14.99 and RX $9.99 up front. RX sells 1 one-off in-app purchase. OB asks for nothing beyond the download.

OB ships an update every 2 months, RX weekly. Both last shipped on October 29, 2026.

## The numbers

| Metric | OB | RX |
| --- | --- | --- |
| Price | $14.99 | **$9.99** |
| Rating | **[4.3 (64 ratings)](https://appshunter.io/ios/app/ob-xd-auv3-synth/id1465262829/reviews)** | — |
| Number of ratings | **64** | — |
| Positive reviews | 57.0% of reviews | — |
| In-app purchases | **No** | Yes |
| Ads | No | No |
| Update frequency | Every 2 months | **Weekly** |
| Monetization | Free | — |
| Best chart rank | **#199** | — |
| Size | 25 MB | 25 MB |
| Requires iOS | 15.0 | 15.0 |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Age rating | 4+ | 4+ |
| Developer | [DiscoDSP LLC](https://appshunter.io/developer/1465262828) | [sung ju KIM](https://appshunter.io/developer/6781333993) |

## What reviewers say

### OB

[App page](https://appshunter.io/ios/app/ob-xd-auv3-synth/id1465262829)

**Currently charting:** #199 Top Paid · Music (US App Store)

This app emulates the classic Oberheim OB-X synthesizer, offering its rich sound and behavior with added enhancements. It focuses on sonic quality and includes micro random detuning for authentic analog warmth. External effects are recommended to further shape its versatile soundscapes.

**Highlights:** Oberheim OB-X emulation, Recreates original sound and behavior, Added enhancements to original design, Micro random detuning, Rich and good sound quality

**Features:** macOS Compatibility

**In-app purchases:** none

**What reviewers like**

- 🎶 Incredible sound quality
- ✨ Inspiring creative tool
- 🎹 Faithful emulation of classic synth
- 🎛️ Great for programming
- 🎚️ Useful presets

**What reviewers complain about**

- 🐛 Unusable UI on older devices
- 💻 Poor GUI scaling on iPad Pro
- 🎛️ Controls unresponsive or misaligned
- 📉 Limited functionality without updates
- 🤷‍♂️ No clear upgrade path

**Reported bugs**

- Crashes in Audiobus
- Cannot use in MIDI section of Audiobus
- Preset browser issues (scrolling, cut off banks)
- Automation bug with cutoff freq
- UI issues on iPad Pro (buttons misaligned, text cut off)

**Requested features**

- Add last/high priority for mono patches
- Increase polyphony to 8 voices
- MIDI Learn functionality
- Preset browser improvements (categories, scrolling)
- Adjustable keyboard size


### RX

[App page](https://appshunter.io/ios/app/rx-79/id6821795679)

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| SJ PACK | $5.99 | one-time |


## Frequently asked questions

### Is OB free?

OB costs $14.99, with no in-app purchases.

### Is RX free?

RX costs $9.99, and also offers in-app purchases.

### Do OB or RX have ads?

Neither OB nor RX shows ads.

### Which is updated more often, OB or RX?

OB ships an update every 2 months, and RX weekly. Most recently, OB was updated on October 29, 2026 and RX on October 29, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*