ThermVoltSilicon vs spool.
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
ThermVoltSilicon
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ThermVoltSilicon is a precise digital recreation of classic silicon diode-based overdrive circuits. It delivers the tighter, brighter, and more articulate character typical of silicon clipping stages, while faithfully modeling analog imperfections such as power supply sag, battery voltage variation, and temperature-dependent diode behavior. Built with the MIT-licensed Patina DSP engine, this AUv3 plugin combines circuit-accurate modeling with modern features for both vintage tone enthusiasts and contemporary producers. FEATURES • Silicon diode clipping with realistic forward voltage and temperature response • Authentic power supply sag and voltage variation (9V / 18V modeling) • Temperature control (15–75°C) affecting diode behavior • Inst / Line input modes with appropriate impedance and gain staging • Switchable Boost stage (+20dB) • Variable high-pass filter • Classic analog-style tone control • 2x / 4x high-quality oversampling • Very low CPU usage, optimized for iOS • AUv3 support with smooth parameter automation SUITABLE FOR • Electric guitar (tight crunch to singing lead) • Bass guitar • Synthesizers & drum machines • Keyboards • Vocals & parallel saturation • Lo-fi, indie, rock, and modern production COMPATIBILITY • AUv3 Plugin • iPhone & iPad (iOS 15+) • AUv3 hosts.
spool.
Create full songs on your phone with this pocket music studio. It offers a variety of sound engines, sampling capabilities, step sequencing, and a 4-track tape recorder for recording and mixing your music. Effects and MIDI controller support enhance the creative process.
- Multiple sound engines
- Sampling and sequencing
- 4-track tape recording
- Extensive effects rack
- MIDI controller support
- Step sequencer
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Make a whole song on your phone. Spool is a pocket music studio inspired by the joy of hardware grooveboxes — play, sample, sequence, and record to tape, all in one playful instrument. Fourteen sound engines. From punchy FM and fat subtractive Pulse to shimmering Cluster, plucked String, granular Cloud, the TALK vocoder, the WIDE stereo engine, THUMP bass, a Sampler, and two drum machines — each with its own animated, touchable visualizer and four hands-on controls. Sample anything. Record straight from the mic into the sampler or drum kits, trim it, and play it across the keyboard. Drums & beats. Build kits, chop a sample into a playable kit, and lock in grooves with the step sequencer. Playful sequencers. Pattern and arpeggiator to start; unlock Stream, Taps, and the bouncing-ball Gumball machine for happy accidents. Six minutes of 4-track tape. Record, overdub, varispeed (including reverse), scrub, and bounce your jam to a finished mixdown — export to WAV. Your tape is saved with your project. Effects & mixer. A deep rack — delay, spring reverb, drive, compressor, chorus, multimode filter, phaser, tremolo/auto-pan, beat-repeat stutter, and a pitch-shifter/harmonizer — many tempo-syncable. Plus a master EQ and brickwall limiter so it always sounds finished. Plays with your gear. Connect a USB or Bluetooth MIDI controller and play Spool like hardware. AUv3 plugin support is planned for a future update. Free to download and make music with a starter set of engines and sequencers. A single one-time Spool Pro purchase unlocks the full instrument — all engines, sampling, every effect and sequencer, unlimited projects, export, and MIDI. No subscription. Spool is an original, independent work by a solo developer — affiliated with no hardware maker.
Screenshots
Verdict
ThermVoltSilicon and spool. are too close to call on the numbers: across 5 compared parameters — price, ads, in-app purchases and device support among them — neither pulls far enough ahead to decide it. What separates them is feature set and interface, not measurable difference.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
Both are free to download. ThermVoltSilicon sells 1 one-off in-app purchase and spool. sells 1 one-off in-app purchase. Whichever you choose, the download price is not the number that matters.
| Parameter | ThermVoltSilicon | spool. |
|---|---|---|
| Price | Free | Free |
| Rating | — | 5.0 (7 ratings) — better |
| Positive reviews | — | 100.0% of reviews |
| Number of ratings | — | 7 — better |
| Ads | No | No |
| In-app purchases | Yes | Yes |
| Monetization | — | Free with in-app purchases |
| Devices | iPhone, iPad | iPhone, iPad |
| Requires iOS | 16.0 — better | 17.0 |
| Further details — not scored | ||
| Size | 28 MB | 2 MB |
| Age rating | 4+ | 4+ |
| Developer | Shoma Kondo | Kristopher Yang |
In-app purchases
ThermVoltSilicon
- ThermVoltSilicon Full Version$4.99
spool.
- Spool Pro$9.99









