A browser-based editor, patch manager & multi-layer loop station for the Valeton GP-200. No install. No account. No backend. Just plug in and play. Free & open source (GPL-3.0).
▶ Open the live app · ☕ Buy me a coffee
The Valeton GP-200 is a great multi-effects pedal with a not-so-great support for linux as the official editor runs on Windows and macOS only, and organizing 256 patches through a 4" screen and two footswitches is nobody's idea of fun.
GP200 Studio fixes that:
- 🐧 Runs anywhere Chrome runs — including Linux. Web MIDI + Web Audio, straight from the browser to the pedal over USB. Nothing to install.
- 🗂️ Real patch management — browse, search, rename, import, export and back up all 256 device slots. Bulk-export your entire pedal to a single ZIP.
- 🎛️ A UI that looks like the gear it edits — your patch is a pedalboard, not a parameter spreadsheet. Every effect is a colorful pedal with knobs you can actually see and turn. See your signal chain at a glance instead of decoding menus.
- 🔁 A loop station the pedal doesn't ship with — a multi-layer looper that records the GP-200's USB audio right in the browser, with MIDI footswitch learn so you can drive it hands-free from the pedal itself.
- 🎸 Pedalboard editor — the whole patch as a stage-styled board: per-effect pedal bodies, drag-to-reorder, FX-loop routing, knob/fader parameter editing, and real-world "based on" info for all 305 effects
- ⚡ Live device push — edits stream to a connected GP-200 over USB-MIDI SysEx as you make them; hardware-side changes sync back into the editor
- 🗄️ Patch manager — full 256-slot list with names & search, activate/open/rename, per-slot
.prstexport/import, one-click bulk ZIP backup - 🦶 Controller assignment — per-patch EXP pedal and CTRL 1–8 footswitch mappings
- 🔁 Loop station — stack unlimited phase-locked layers over the GP-200's USB audio, with MIDI-learn to bind transport controls to the pedal's footswitches
The GP-200's built-in looper records a single loop. GP200 Studio turns the pedal into a legit multi-layer loop station: connect a laptop, an Android phone, or anything else that runs Chrome over the same USB cable you already use, and the app records the pedal's USB audio right in the browser.
- 🎚️ Unlimited layers — your first recording sets the master loop; every record pass after that adds a new track, quantized and phase-locked to it, so everything stays locked in time no matter how many layers you stack
- 🎛️ Per-layer control — each track has its own play/pause, mute, volume, and delete, plus a master progress bar and one-click Clear All
- 🦶 Hands-free from the pedal — MIDI-learn binds the GP-200's physical footswitches to Record, Play, and track selection, and a takeover mode stops those stomps from firing their normal patch functions while you loop
- 🥁 Backing rhythm — the drums drawer remote-controls the pedal's built-in drum machine (and its stock single-track looper and tuner) over MIDI, so you can loop against a beat
No audio interface, no DAW, no extra pedal — just the GP-200, a USB cable, and a browser.
📸 More screenshots
| Landing | FX-loop routing |
| EXP pedal assignment | CTRL footswitch assignment |
| Signal chain & effect info | Export |
- Open GP200studio in Chrome or Edge
- Plug your GP-200 into USB and hit CONNECT GP-200 — or hit Open editor to work on
.prstfiles offline - That's it. Everything runs client-side; your presets never leave your machine.
git clone https://github.com/kabir0st/gp200-studio.git
cd gp200-studio
npm install
npm run dev # http://localhost:5173Other useful commands: npm run build, npm run typecheck, npm run lint, npm run test.
Everything is client-side TypeScript. A pure protocol layer in src/core/ decodes/encodes the GP-200's binary .prst preset format (byte-exact round-trips via raw-source passthrough) and speaks the pedal's reverse-engineered USB-MIDI SysEx protocol — parameter changes, effect swaps, toggles, reorders, preset pulls and saves — over the browser's Web MIDI API. React hooks layer connection/session handling on top, and the pedalboard UI sits on that. No server is involved at any point.
GP200 Studio is open source and contributions are welcome — bug reports, protocol captures from your hardware, and pull requests alike. Open an issue or PR on GitHub. If the app saves you from the 4" screen, you can also buy me a coffee. ☕
- Built on the reverse-engineering groundwork of phash/gp200editor — the
.prstbinary format, SysEx MIDI protocol, and 305-effect mapping - Built by Kabir Tamari
GPL-3.0 — free to use, study, share, and improve; derivatives must stay open source.