Comparison

Kauldron Synthesizer vs NuRack Auv3 FX Processor

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

Head to head
About

Kauldron Synthesizer

This app combines classic analog synth warmth with AI-powered sound design. It offers intelligent preset generation, extensive modulation options, and a powerful arpeggiator for creating rich synth textures.

Highlights
  • AI-powered preset generation (SPAWN²)
  • Analog modeling oscillators
  • Extensive modulation matrix
  • Dual XY-pads for control
  • Powerful arpeggiator
  • AUv3 plugin support
  • Over 900 presets
Read full description

Kauldron is where classic warmth meets Artificial Intelligence. One of our toniest and punchiest synths, Kauldron features a completely new analog modeling technology. The full spectrum of rich synth textures is bolstered by the groundbreaking SPAWN intelligent preset generation system that allows new patches to be created at the touch of a button. Abounding with pure hard-hitting tones, Kauldron requires little to no FX or production gimmicks to sound big. Kauldron is designed with modulation and fine dynamic control in mind. The two fully-featured LFOs and the mod envelope combine with a wide variety of MIDI learnable controls to manipulate multiple parameters. Everything is easily set up in a clearly laid out ‘mod matrix.’ The dual XY-pads can be used for controlling modulation or a wide range of synth parameters. MIDI aftertouch can be routed via the matrix for even greater control over expression and tonality. Kauldron also debuts the next generation of our Artificial Intelligence preset creation system, SPAWN². Completely reimagining the groundbreaking SPAWN algorithms in our hugely popular Magellan, the new SPAWN² gives you unprecedented control over generating presets. In the expert mode, you can accomplish anything from subtle ‘variations on a theme’ to bold new sounds. In the basic mode, where Kauldron does all the thinking, you get preset after usable preset with just a touch. This is not simple randomization: it is the power of A.I. put to benevolent use! Kauldron also includes its AUv3 plugin version so that you can seamlessly run multiple instances in your favorite DAW. Powerful arp with both live & program modes; comprehensive MIDI features with effortless MIDI learn; over 900 presets; recording, sharing, these are just some of the features brewing inside Yonac’s Kauldron. Selected specs include, SYNTH • 3 analog modeling oscillators w/ multiple waveforms & true PWM • FM via Osc 2 • Maximizer module with drift, spread & voice count for huge, stereophonic all-synth sounds • New vAnalog filter design w/ ‘dirt’ overload for even warmer, harmonically complex tones • Dedicated filter ADSR envelope • Filter tracking, contour & more • Pink/white noise generator • Osc. phase reset & sync • Retro & modern glide algorithms • Virtual VCA envelope with 2 attack types • Poly/mono operation • Legato mode for buttery smooth passages • Extensive modulation options via the ‘mod matrix’ • 2 LFOs w/ BPM sync, keytracking, trigger mode & more • Assignable mod envelope • 23 mod targets • 11 mod controllers, including aftertouch, velocity & keytracking • 2 XY-Pads for controlling mod targets or synth parameters • Arpeggiator with live & program modes, 11 algorithms, gate, swing, note value, octaving & more • Stereo mod effect with chorus & flanger modes • BPM-syncable stereo delay • Studio quality reverb w/ 7 room types, damping, time & mix • 900+ presets in a wide variety of styles & sounds SPAWN² • Automatic preset generation via artificial intelligence • Generate infinite new, usable presets at the touch of a button • Expert mode lets specify Variation & Autonomy for each major synth module • 3 unique A.I. algorithms • Auto arp programming in any listed scale PRO FEATURES • AUv3 - use as Audio Unit instrument plugin on iPad & iPhone • Fullscreen AU mode • Extensive MIDI: MIDI learn, aftertouch, MIDI CC map save/share, KB mapping, program changes & more APP • iPhone & iPad Compatibility • Powerful YPAT2 preset management system • Classic or ribbon key controller • Ribbon controller: Poly aftertouch into Kauldron • Ribbon controller: Settable musical key & scale • Classic KB: Velocity w/ sensitivity setting • Tapedeck: Record, loop & share • Metronome • Tap BPM

About

NuRack Auv3 FX Processor

Design custom audio and MIDI effects racks with over 80 building blocks. Route audio in series or parallel and create unique interfaces for your sound processing needs.

Highlights
  • Design custom effects racks
  • Over 80 audio and MIDI building blocks
  • Full routing control (series/parallel)
  • Customizable interface builder
  • Seamless effect switching
  • 3 independent audio racks mode
  • Extensive automation options
Read full description

NuRack is an AUv3 based multi-channel audio and MIDI effects processor with a difference, it actually allows you to design your own custom effects using the 80+ building blocks provided. You have full control over routing which allows you to create complex audio paths in series or parallel. You can choose whether to use the stock interface or create your own custom interface using the built in Interface Builder which allows you to concentrate your audio components into a single customized effect. NuRack can run in one of two modes. The first providing 3 customizable effects racks which can be switched (manually or via MIDI), providing seemless switching (i.e. delay trails linger whilst another set of effects are faded in). The second mode allows you to route audio through 3 independent audio racks. A generaous number of over 80 audio and midi building blocks are provided covering 12 different categories of effects. Here are just some of those included in NuRack: Modulation Effects: Chorus, Flanger, Phaser, Tremolo, Vocal Doubler, TalkBox, UniVibe, Leslie & Vocoder. Time Based Effects: Stereo Delay, Tape Delay, Reverb and Reverse Delay. Spectral Effects: Parametric EQ, Graphic EQ, PitchShift, Auto-Pan, Bit-Crusher, Tube Overdrive, Distortion, Harmony, Harmonic Exciter and SlowMo. Dynamic Effects: VelocityControl, Compressor, Multi-Band Compressor, Noise Gate, Gate, and Limiter. Filter Effects: MultiFilter, LP/HP Filter, Frequency Splitter, MultiBand Splitter, Classic Filters, Formant Filter, Ring Modulation and Shelf Filter. MIDI Effects: MIDI Harmony, MIDI Velocity, MIDI Randomizer, MIDI Monitor, MIDI Mixer, MIDI Pads, MIDI Control, Strummer, MIDI Recorder, MIDI Modulation, MIDI Remap, CC Monitor, CC Generator, PitchBend, MIDI Time Clock, and ChordToMidi. Generator Modules: Noise, Audio Clip Launcher, SoundFont Player, Virtual Flute, Virtual Clarinet, Virtual Brass, FM Organ, FM Rhodes and Analog Sawtooth Synth. Automation: TouchPad, AutoMate, Pattern Automation, and Visual LFO. You also provide the ability to split and combine audio signal using splitters and mixer modules as well as a number of visual elements such as VU Meters, LED Meters, Scopes, Graphs etc. Some effects such as phaser and flanger are usually controlled by an LFO, but this can be detached and automated remotely. There are a number of modules that allow auomation based on direct touch (X/Y Pads), Visual LFO, Pattern Automation, MIDI input (CC data), or peak/rms level detection. These automation modules can remotely control knobs and sliders throughout your rack. Simply create a new rack and start adding modules to it. These modules are generally wired up automatically but these connections can be manually routed. Once you have your sound as you wish you can use it 'as is', or switch to Interface Builder mode where you can combine all your modules into a single interface. Elements can be dragged, dropped, resized and coloured as required. Add your own labels, image logos and custom backgrounds before saving your custom component. Use the X/Y Pad to control your modulation effects by detaching their LFO's. Use MIDI CC data to automate knobs. Use the velocity of an incoming signal to control the cutoff/resonance of a filter (wah) or volume level of a gain control (swell), as NuRack expands, so do the possibilities. Features: ○ Over 80 categorised modules. ○ 3 Input / Output busses supported. ○ Audio & MIDI effect. ○ Lots of audio & MIDI automation options. ○ Seemless transition between racks. ○ Manual audio path routing. ○ Open in presentation mode (auto hides controls). ○ Interface Builder to customize your rack. ○ AUv3 plugin runs in MIDI and none MIDI mode. ○ Add your own Text/Heading and Image/Logos and backgrounds to your design. ○ Compatibility options for DAW's not supporting multi-channels. ○ Dark/Light Modes Checkout the YouTube channel 'Paul the MusicMan' for demos and tutorials of NuRack.

Screenshots

Kauldron Synthesizer4 screens
NuRack Auv3 FX Processor4 screens

Verdict

The call

The clearest difference is update cadence: NuRack Auv3 FX Processor at every 3 weeks against Kauldron Synthesizer's every 49 months. NuRack Auv3 FX Processor also leads on iOS requirement (13 vs 15.6). Kauldron Synthesizer's advantage is price ($9.99 vs $12.99) and ratings volume (136 vs 41). On rating, review sentiment, ads and in-app purchases 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

Kauldron Synthesizer costs $9.99 and NuRack Auv3 FX Processor $12.99 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 — 4.6 for Kauldron Synthesizer against 4.7 for NuRack Auv3 FX Processor. Both are backed by a comparable volume of ratings — 136 and 41 respectively. Written reviews are what separate them: 80% of Kauldron Synthesizer's written reviews are positive against 84% of NuRack Auv3 FX Processor's.

UpkeepUpdate frequency

Kauldron Synthesizer ships an update every 49 months, NuRack Auv3 FX Processor every 3 weeks. The most recent releases landed on October 20, 2026 and October 25, 2026 respectively.

Scorecard4 real differences · 6 level
Kauldron Synthesizer versus NuRack Auv3 FX Processor: the parameters behind the verdict, then further details
ParameterKauldron SynthesizerNuRack Auv3 FX Processor
Price$9.99 — better$12.99
Rating4.6 (136 ratings)4.7 (41 ratings) — better
Positive reviews79.7% of reviews84.4% of reviews — better
Number of ratings136 — better41
Update frequencyEvery 49 monthsEvery 3 weeks — better
AdsNoNo
In-app purchasesNoNo
MonetizationPaidPaid
DevicesiPhone, iPad, iPodiPhone, iPad, iPod
Requires iOS15.613 — better
Further details — not scored
Size32 MB26 MB
Age rating4+4+
DeveloperYonac Inc.4Pockets.com

Customer experience

Kauldron Synthesizer

All ratings136 ratings
Positive88.2%
Neutral6.6%
Negative5.1%
Written reviews74 reviews
Positive79.7%
Neutral9.5%
Negative10.8%

NuRack Auv3 FX Processor

All ratings42 ratings
Positive92.9%
Neutral2.4%
Negative4.8%
Written reviews32 reviews
Positive84.4%
Neutral6.3%
Negative9.4%

Bugs and requests

Kauldron Synthesizer

Reported bugs

15 issues
  • Oscillators cannot be set to -1 octave
  • Shrill noise
  • No Bluetooth speaker output
  • Fails to reload with Logic projects
  • Cannot load into Logic Pro
Show 10 more
  • Starts and quits on latest iOS
  • AUv3 bug: receives notes regardless of track selection
  • AUv3 implementation flaky, random crashes
  • AUv3: plays all instances simultaneously
  • Bug with Garageband: duplicates patterns
  • MIDI learn functions not saved
  • Sometimes glitchy
  • XY pad movements not recorded as automation
  • CPU killer on iPad 4
  • No function to share sounds

Requested features

11 requests
  • Bring synths/effects to macOS
  • Mac App version
  • More comprehensive FX section (distortion/saturation)
  • MIDI-out for arpeggiator
  • Drum machine, PAD launcher, DAW
Show 6 more
  • Browser download feature
  • Sequencer in Kauldron
  • Effects tool
  • Version history
  • More developer responses/support
  • Dark mode option

NuRack Auv3 FX Processor

Not enough reviews yet to summarise bugs or requests.

In-app purchases

None

Kauldron Synthesizer

No in-app purchases

None

NuRack Auv3 FX Processor

No in-app purchases

Questions

Is Kauldron Synthesizer free?
Kauldron Synthesizer costs $9.99, with no in-app purchases.
Is NuRack Auv3 FX Processor free?
NuRack Auv3 FX Processor costs $12.99, with no in-app purchases.
Which has better reviews, Kauldron Synthesizer or NuRack Auv3 FX Processor?
NuRack Auv3 FX Processor is rated higher. Kauldron Synthesizer averages 4.6 out of 5 from 136 ratings, while NuRack Auv3 FX Processor averages 4.7 from 41 ratings.
Do Kauldron Synthesizer or NuRack Auv3 FX Processor have ads?
Neither Kauldron Synthesizer nor NuRack Auv3 FX Processor shows ads.
Which is updated more often, Kauldron Synthesizer or NuRack Auv3 FX Processor?
Kauldron Synthesizer ships an update every 49 months, and NuRack Auv3 FX Processor every 3 weeks. Most recently, Kauldron Synthesizer was updated on October 20, 2026 and NuRack Auv3 FX Processor on October 25, 2026.

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