Comparison

GSDSP Quantum Delay vs isfizz

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

GSDSP Quantum Delay

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
Read full description

A vintage-inspired delay supercharged with deep modulation, flexible filtering, and creative timing that pushes echoes into new dimensions. Classic Delay, Reinvented Quantum Delay takes the charm of a vintage stereo delay and fuses it with our next-level modulation system. Switch between the warm character of Tape mode and the pristine clarity of Fade mode, lock to BPM (including 5-tuplets) or dial in precise times in milliseconds. Use the Fine control for subtle push-and-pull micro-timing — or modulate your delay lines in ways traditional delays could only dream of. Sculpted Echoes Shape your repeats with switchable lowpass, highpass, and bandpass filters placed directly in the feedback path. Add modulation to create evolving tones, gentle movement, or drifting, frequency-shifting echoes. From warm analog-style rolls to shimmering, swirling textures, it’s all there. Feedback with Precision Control your delay tail behavior using either traditional % feedback or our modern dB-per-second decay system — ideal for predictable, musical decay even when the feedback path becomes complex. Enable Crossfeed for classic ping-pong stereo bounce, or push into Over-Feedback to create dense, self-building echoes that drift toward infinity. Stereo or Dual Mono Every section of Quantum Delay — delay, filter, and feedback — can switch between stereo and dual mono modes. Create tight, controlled stereo images or break them apart for wide, offset, unpredictable spaces. Dual mono modulation unlocks complex stereo interplay and beautifully asymmetric echoes. Modulation Without Limits Quantum Delay integrates our advanced modulation system, letting you modulate nearly anything: delay time, filters, feedback parameters, stereo controls, and more. Use LFOs, Random Generators, 2D modulators, Envelope Followers, Macros, and even chaotic systems to push your echoes far beyond traditional delay behavior. Or use our parameter randomisation feature to explore the plugin’s sound at random. Quantum Delay is an AUv3 audio effect plugin compatible with Logic Pro, AUM, Cubasis, GarageBand and many more. A Desktop version is also available for Windows and macOS (VST3 / AU / AAX). More information here: https://gs-dsp.com/products

About

isfizz

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
Currently charting
Read full description

isfizz is a SFZ file player. SFZ is an open text format for sampled sound instruments. This app can load SFZ and play the instrument. - Includes Audio Unit Extension (AUv3). - You can edit SFZ string. - The app loads SFZ files in place without copying the files. - Double tap to enter the value, triple tap to reset. - Supports Scala tuning files (.scl). - Supports MIDI. - Supports 16 out. use the "output=N" opcode in SFZ. Supported sample file format: - .wav (raw PCM) - .aiff - .mp3 - .flac - .ogg (vorbis) - .wv (wavpack) This app is an iPhone/iPad port of sfizz-ui project. The app is made from some sfizz-ui codes and images. About half of the income from this app will be donated to SFZ Tools team. This app and the description contain machine translated text.

Screenshots

GSDSP Quantum Delay3 screens
isfizz4 screens

Verdict

The call

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.

Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS

CostPrice · In-app purchases · Ads · Monetization

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.

ReceptionRating · Positive reviews · Number of ratings

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.

UpkeepUpdate frequency

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.

Scorecard4 real differences · 7 level
GSDSP Quantum Delay versus isfizz: the parameters behind the verdict, then further details
ParameterGSDSP Quantum Delayisfizz
Price$14.99$2.99 — better
Rating4.8 (17 ratings) — better4.7 (14 ratings)
Positive reviews100.0% of reviews100.0% of reviews
Number of ratings17 — better14
Update frequencyEvery 5 weeksFortnightly — better
AdsNoNo
In-app purchasesNoNo
MonetizationPaidPaid
Best chart rank—#188 — better
DevicesiPhone, iPad, iPodiPhone, iPad, iPod
Requires iOS12.0 — better15.0
Further details — not scored
Size94 MB6 MB
Age rating4+4+
DeveloperGustav ScholdaRyouta Kira

Customer experience

GSDSP Quantum Delay

All ratings17 ratings
Positive94.1%
Neutral0.0%
Negative5.9%
Written reviews4 reviews
Positive100.0%
Neutral0.0%
Negative0.0%

isfizz

All ratings14 ratings
Positive92.9%
Neutral0.0%
Negative7.1%
Written reviews6 reviews
Positive100.0%
Neutral0.0%
Negative0.0%

In-app purchases

None

GSDSP Quantum Delay

No in-app purchases

None

isfizz

No in-app purchases

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.

Other comparisons