Valeton GP-50 Editor

A browser-based editor for the Valeton GP-50 (and GP-5), built by reverse-engineering the pedal's MIDI SysEx protocol from scratch. It reads and writes the device live over WebMIDI — no vendor SDK, no drivers, no backend.

Live demo: valeton-gp50-woad.vercel.app — zero-setup, runs entirely in-browser. Chrome or Edge, pedal on USB.

What it does:

• Preset Explorer — reads every preset off the connected pedal; full signal chain per preset, block chips color-coded by type.
• Live editing — edit a preset's blocks, models, and parameters in the browser; changes mirror straight to the pedal over WebMIDI.
• Model picker — swap any block's model using Valeton's official hardware names, not just internal IDs.
• Preset rename — edit a preset's name and write it back to the device.
• Preset & block reordering — drag to rearrange presets in a bank, or blocks within a preset's signal chain; each reorder is one batched, minimal write.
• Clear Preset — wipe a slot back to a factory-blank preset.
• Captures & IRs browser — every SnapTone capture and User IR on the device, plus reusable templates.
• Capture usage lookup — pick a SnapTone or IR and see exactly which presets reference it.
• Build a patch from a capture — wrap a template's effects chain around a SnapTone/IR and write the result to a slot.
• Make a template from a preset — save any preset's effects chain as a reusable template.
• Preset Converter — convert .prst preset files between the GP-5 and GP-50 formats, entirely client-side.

Everything above runs client-side. The live demo is the whole app; the local FastAPI server (Setup) is only for development and for the legacy in-repo NAM converter.

Getting NAM captures onto the pedal

That moved to its own project: nam-a2a1-converter — a standalone desktop app (Windows / macOS / Linux, optional NVIDIA acceleration). Download a release →

The GP-50 only accepts NAM A1, and there's no A2→A1 format downgrade — they're different neural architectures, so the weights don't transfer. The converter distills instead: render a DI through the A2 model, then train an A1 to reproduce that output. It's device-agnostic, so it serves any A1-only device or plugin, not just the GP-50.

This repo still carries the engine it grew out of (a2a1/, wired into the local app), but the converter you actually want is the standalone one.

Screenshots

Preset Explorer — every preset on the pedal, block chips color-coded by type.	Preset detail — full signal chain, per-block params, live edit straight to the pedal.
Model picker — swap a block's model, official hardware names included.	Captures & IRs — saved templates plus every SnapTone capture on the device.
Capture usage — see exactly which patches reference a SnapTone.	Build a patch — wrap a template around a SnapTone and write it to a slot.
Make a template — save any preset's effects chain as a reusable wrapper.	Preset Converter — convert .prst presets between the GP-5 and GP-50.

Setup

You don't need any of this to use the app — open the live demo. Local setup is for development.

cd /Users/drewmerc/workspace/valeton

# web app venv
python3 -m venv .venv-app && ./.venv-app/bin/python -m pip install fastapi "uvicorn[standard]" python-multipart pytest httpx

Optional: the in-repo NAM engine (superseded by nam-a2a1-converter)

# engine venv (A2 render + train + 0.7.0 export; 0.5.x via in-process transcode)
python3 -m venv .venv && ./.venv/bin/python -m pip install -r a2a1/requirements-a2.txt   # NAM 0.13.0

One venv, not two — see a2a1/README.md for why the old second one is gone. The default DI is refs/v3_0_0.wav (official NAM input). Get it via the trainer, or generate a synthetic fallback: ./.venv/bin/python a2a1/make_di.py refs/v3_0_0.wav.

Run

./run.sh

Then open http://127.0.0.1:8756.

• Preset Explorer / Captures & IRs: connect the pedal over WebMIDI (Chrome/Edge, HTTPS or localhost), scan, and browse/edit real device data live — see the itemized feature list above.
• Preset Converter: drop in a .prst and convert between GP-5 and GP-50 formats.
• NAM converter: present in the local build only, and only with the engine venv above. The hosted build links to the standalone converter instead.

Tests

./.venv-app/bin/python -m pytest app/tests -q -m "not slow"   # fast unit/API/frontend suite
./.venv-app/bin/python -m pytest app/tests/test_e2e.py -q -s  # slow: real headless browser conversion + screenshots

Layout

• app/ — the FastAPI web app + the WebMIDI frontend (device I/O, decoders, editor UI).
• a2a1/ — GP-50 MIDI RE tooling, plus the original A2→A1 engine (README); the shipped converter now lives in nam-a2a1-converter.
• docs/, re/, design/ — protocol notes, RE captures, and format research.
• refs/ — sample models + the DI input.
• MVP_REQUIREMENTS.md, AUTONOMY.md, STATUS.md — the MVP spec, the build-loop protocol, and live build status.

License

MIT

Scope

Live device read/write (Explorer, live edit, reorder, rename, clear, capture usage, build/make-template) is reverse-engineered and working over WebMIDI. The app only talks to the physical pedal when you explicitly connect and scan/write via the Explorer or Captures & IRs pages.