# GSDSP Quantum Delay vs isfizz

The clearest difference is price: isfizz at $2.99 against GSDSP Quantum Delay's $14.99. isfizz also leads on update cadence (fortnightly vs every 5 weeks) and chart position (#188 vs unranked). GSDSP Quantum Delay's advantage is iOS requirement (12.0 vs 15.0). On rating, review sentiment, ratings volume and ads there is nothing between them.

GSDSP Quantum Delay costs $14.99 and isfizz $2.99 up front. Neither carries in-app purchases, so what you see is what you pay.

On the App Store both sit at effectively the same score — 4.8 for GSDSP Quantum Delay against 4.7 for isfizz. Both are backed by a comparable volume of ratings — 17 and 14 respectively. Written reviews split almost evenly too, at 100% and 100% positive.

GSDSP Quantum Delay ships an update every 5 weeks, isfizz fortnightly. The most recent releases landed on September 22, 2026 and September 19, 2026 respectively.

## The numbers

| Metric | GSDSP Quantum Delay | isfizz |
| --- | --- | --- |
| Price | $14.99 | **$2.99** |
| Rating | **[4.8 (17 ratings)](https://appshunter.io/ios/app/gsdsp-quantum-delay/id6469328297/reviews)** | [4.7 (14 ratings)](https://appshunter.io/ios/app/isfizz/id6470708963/reviews) |
| Number of ratings | **17** | 14 |
| Positive reviews | 100.0% of reviews | 100.0% of reviews |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | Every 5 weeks | **Fortnightly** |
| Monetization | Paid | Paid |
| Best chart rank | — | **#188** |
| Size | 94 MB | 6 MB |
| Requires iOS | **12.0** | 15.0 |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Age rating | 4+ | 4+ |
| Developer | [Gustav Scholda](https://appshunter.io/developer/1642323227) | [Ryouta Kira](https://appshunter.io/developer/862984358) |

## What reviewers say

### GSDSP Quantum Delay

[App page](https://appshunter.io/ios/app/gsdsp-quantum-delay/id6469328297)

This app offers a vintage-inspired stereo delay effect with advanced modulation, flexible filtering, and precise timing controls. It allows users to sculpt unique echo textures, from warm analog sounds to complex, evolving soundscapes.

**Highlights:** Vintage-inspired stereo delay, Deep modulation system, Flexible filtering (LPF, HPF, BPF), Precise timing controls (BPM, ms), Switchable stereo/dual mono modes, Advanced modulation sources (LFO, Random, Envelope)

**Features:** Vision Pro support

**In-app purchases:** none


### isfizz

[App page](https://appshunter.io/ios/app/isfizz/id6470708963)

**Currently charting:** #188 Top Paid · Music (US App Store)

This app plays SFZ files, an open format for sampled sound instruments. It supports various audio file formats, MIDI, and Scala tuning files. It also functions as an Audio Unit Extension (AUv3) for use with other music apps.

**Highlights:** SFZ file playback, Audio Unit Extension (AUv3) support, Edit SFZ strings, Load SFZ files in place, Scala tuning file support, MIDI support

**Features:** Vision Pro support

**In-app purchases:** none


## Frequently asked questions

### Is GSDSP Quantum Delay free?

GSDSP Quantum Delay costs $14.99, with no in-app purchases.

### Is isfizz free?

isfizz costs $2.99, with no in-app purchases.

### Which has better reviews, GSDSP Quantum Delay or isfizz?

GSDSP Quantum Delay is rated higher. GSDSP Quantum Delay averages 4.8 out of 5 from 17 ratings, while isfizz averages 4.7 from 14 ratings.

### Do GSDSP Quantum Delay or isfizz have ads?

Neither GSDSP Quantum Delay nor isfizz shows ads.

### Which is updated more often, GSDSP Quantum Delay or isfizz?

GSDSP Quantum Delay ships an update every 5 weeks, and isfizz fortnightly. Most recently, GSDSP Quantum Delay was updated on September 22, 2026 and isfizz on September 19, 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.*