Zoom MultiStomp ZDL

Custom .ZDL effects for Zoom MultiStomp pedals, plus the reverse-engineered toolchain used to build them — no Zoom SDK required.

This was a good amount of work and tokens, please consider to Sponsor this project or Buy me a coffee

Video tutorial — what this is, how it works, and turning a NAM capture and a cab IR into effects for the pedal:

In the press: Vibe coding is turning the music gear world upside down (The Verge, Terrence O'Brien, October 19, 2026) features this project and the MS-70CDR work.

New here? This is a pack of 22 extra effects plus a free browser-based Patch Editor for adjusting knobs and arranging effects in your patches. On the original MS-70CDR, you install the ready-made files from dist/ over USB using Zoom Effect Manager—no custom firmware reflash, coding, or compiling needed. Back up your patches and effect list first. The Patch Editor edits patches; Zoom Effect Manager installs the effects. See the installation guide.

Pedal compatibility:

• Tested: original MS-70CDR (firmware 2.10)—custom effects and Patch Editor.
• Confirmed by a user: MS-50G (firmware 3.10): NAM captures (full rate and Eco) and CabIR work (#5). Patch Editor writes passed the opt-in write test on that pedal (save, backup and restore worked); still experimental.
• Compatible family, awaiting confirmation: MS-60B, G1on, G1Xon, B1on and B1Xon. Custom effects and Patch Editor compatibility on these models is awaiting confirmation from users.
• Works with third-party tools: MS-100BT. It has no USB MIDI, so Effect Manager and Patch Editor can't reach it; effects go on over Bluetooth with lopezchau's MS-100BT tools or MS StompCtrl. A user confirmed Shatter, Galactic, Microloom and Spool running (#4); NAM and CabIR are untested there.
• Not supported: the Plus models (MS-50G+, MS-60B+ and MS-70CDR+) and the Four series (G1/G1X Four, B1/B1X Four, A1/A1X Four). They use Zoom's newer ZD2 effect format, so ZDL files don't load on them. See Compatibility below and the pedal research notes.
• NAM on a Plus pedal: use nam2zoom by Aleksandar Vukasinovic instead (not this project). It packs 1-10 NAM captures into one MS Plus effect; tested on the MS-50G+ and MS-70CDR+, experimental on the MS-60B+.

Custom NAM captures and cabinets (experimental)

Load your own amp captures (NAM) and speaker cabinets (IRs) onto the pedal. Everything runs in your browser — no compiler, nothing uploaded anywhere.

Beta — testers wanted. Only tested on one MS-70CDR so far. Other models may hit DSP full sooner or crackle. Keep a backup of your patches, and read If the pedal freezes before you install anything. Please report what you find with the NAM / Cab report form — results from pedals other than the MS-70CDR are especially useful.

How to use it

1. Open the NAM + Cab Loader (Patch Editor Settings → Custom NAM captures, with the local editor running).
2. Amp: drop in an A2 Lite .nam file, give it a short name, pick an icon and a slot, download the .ZDL and its thumbnail. Pick Eco or Eco+ if you want it lighter on the DSP (see below). Pick a Split output to get the amp on one output and your clean guitar on the other.
3. Cab: drop in an IR .wav (44.1 or 48 kHz). The loader fits it to a small filter the pedal can afford and gives you a .ZDL; pick an icon per cab.
4. Install the files with Zoom Effect Manager. They appear in Patch Editor under the names you chose, as NAM-<name> and CAB-<name> on the pedal.

Slots. 216 amp slots and 216 cab slots, each with its own effect ID, so you can keep as many installed side by side as the pedal's storage holds (each file is ~30 KB for a capture, ~16 KB for a cab). Putting a new capture in a used slot replaces the old one (patches that used that slot pick up the new sound). Filenames encode the slot so they never collide: NAM4smok.ZDL, NAM150sm.ZDL, C01sm57.ZDL, C150sm5.ZDL. Names must start with a letter.

Your name and icon on the pedal. Each file's pedal-screen picture shows the name you typed and one of 21 icons (amp, cab, speaker, tube, mic, skull, flame…); the Effect Manager thumbnail the loader gives you matches it.

A capture, smokey, amp icon

A cab, 4x12, cabinet icon

Knobs.

Effect	Knobs
NAM	Input, Output, Mix, Bass, Mid, Treb, Gate (noise gate; 0 = off)
NAM, split	Input, Output, Dry (the dry side's level: 50 = unchanged, -24 to +24 dB), Bass, Mid, Treb, Gate
CabIR	Mix, Level, Reso (low-end resonance), Pres (presence)

DSP budget. The pedal refuses a patch (shows DSP full) once the summed cost of its effects goes over about 225. Patch Editor now has a DSP meter in the toolbar that adds up the chain for you (amber from 80%, red when the pedal will refuse it).

Effect	Declared cost	Notes
NAM, full rate	194	Best sound. Leaves room for one light effect (a drive, a cab).
NAM, Eco	181	Runs the model on 6 of every 8 samples. Within 0.3 dB of full rate below 3 kHz, a little less treble above.
NAM, Eco+	152	Half rate, with a correction EQ the loader fits to each capture. Sounds noticeably worse than full rate, but leaves room for more effects. For amp-only captures into a cab.
CabIR	10	32-tap filter + 6 EQ bands; fits next to any NAM.

What works. A2 Lite captures only (the small standard NAM architecture). Larger NAM models don't fit this DSP. Captures trained at 48 kHz work, but retraining at 44.1 kHz (the pedal's rate) is closer to the real amp; we used NAM ReTrainer by Alexander Lim (Leemuzhko) for that. The cab fit follows his Hybrid IR idea (HYBRID-IR): a short filter plus a few EQ bands instead of a long IR, so a cab costs almost nothing.

Your captures stay yours. .nam files, fitted cabs and the .ZDL files built from them are gitignored (dist/NAM*, dist/C[0-9][0-9]*, archives). The templates in tools/nam_template*/ and tools/cab_template/ hold no capture data — the loader only fills in the weights and the name.

See the loader guide for details, docs/NAM-RUNTIME-INVESTIGATION.md for how the engine was made to fit, and src/hardware_probes/cab_ir/README.md for the cab engine.

Quickstart — edit your pedal from the browser

▶ Open the Patch Editor

Plug the MS-70CDR in over USB, click Connect, and edit patches live — no install, no clone, nothing sent anywhere (it is one self-contained HTML file and your patch library lives in your own browser).

• Opera or Edge. Safari and Firefox do not implement Web MIDI; the editor will tell you if you are on one of them. Chrome 152 is currently broken — a Web MIDI input regression means output works, no dump ever arrives, and no error is raised. tools/midi_check.html confirms it in isolation.
• Install effects without Effect Manager (MS-70CDR, new): Effects in the toolbar lists this project's effects with the version on your pedal, and installs, updates or removes them over USB. It never touches Zoom's own effects, checks names and effect IDs against everything on the pedal, reads back every write, and can back up all the pedal's files first. Power-cycle the pedal after a change. Tested on firmware 2.10 (how it works).
• Close Zoom Effect Manager first — it holds the MIDI port. "The pedal did not respond" is usually this.
• Slots 1–3 respond to knob moves instantly. Slots 4–6 cannot be edited live by this hardware, so the editor applies those for you — see docs/MIDI-PARAM-EDIT.md. Effects built before 2026-09-10 also load with their knobs inert until nudged; rebuild or reinstall from dist/ and that goes away.

▶ Open the Cover Editor — draw the 128×64 image an effect shows on the pedal's screen. Drawing, PNG/JSON export and the device preview all work from the link above; the one-click Update ZDL button additionally needs the local build server:

git clone https://github.com/themanro/ZoomMultistompZDL.git
cd ZoomMultistompZDL
python3 tools/serve_editor.py        # opens the editor, wires up "Update ZDL"

Loading new effects onto the pedal still goes through Zoom Effect Manager — the browser can edit patches, but it cannot install effects.

Custom effect pack

September 14 display update: all 22 effects now have individual laboratory-inspired graphics, corrected LCD proportions, and shorter pedal labels. Mode controls show names in PE and supported custom effects show short names on the pedal. Reinstall the updated files from dist/ to get the pedal artwork and labels; refresh the Patch Editor for its UI changes. Existing patch values and effect IDs are preserved. See the display update notes for details.

This fork ships a curated library of 22 effects — all grouped under the Delay category, each with a custom on-device cover. Eighteen originals, three Airwindows-derived ports (Galactic reverb, Oxide tape, Spool tape echo), and one contributed effect (Dustbox). Full knob layouts, caveats and sound demos are in CUSTOM_EFFECTS.md.

What each one does

Knob lists are read from the shipped dist/ binaries, so they match what the pedal actually shows.

Effect	Knobs	What it is
Microlm	Pitch, Regen, Tone, Mix	granular pitch-shimmer cloud; grains are pitched and fed back, so it builds rather than repeats
Flower	Rate, Mix	Korg-style random sample-and-hold step filter — the "Digital Bath" sound
Shatter	Chance, Mix	stutter / beat-repeat glitch for drums
Arrakis	Detune, Mix	Dune-style detuned sub-octave drone, two subs beating against each other
Corrupt	Sub, Tone, Wave, Mix	EQD Data Corrupter-style PLL square synth with tracked sub and divided harmony
Klang	Freq, Sweep, Mix	swept-carrier ring modulator — sirens, dive bombs, clangorous metal
GenLoss	Wow, Tone, Hiss, Mix	tape/VHS generation loss: wow, head-bump tone shift, hiss
Scorch	Gain, Mix	aggressive high-gain amp with a cab-style filter (cab baked as biquads, not an FIR)
Howl	Tune, Annihil, Mix	DBA Total Sonic Annihilation-style feedback loop that self-oscillates on demand
Taffy	Speed, Chance, Depth, Glide, Mix	Red Panda Tensor-style tape warp — reverse, stop, double-speed, random slips
Dissolve	Chance, Smear, Glitch, Mix	OBNE Parting-style glitch delay dissolving into a reverb wash
Mangle	Time, Feedbk, Crush, Tremolo, Pitch, Mix	delay with three blendable per-repeat mutations; all three at 0 is a clean delay
Rooms	Mode, Time, Freq, Depth, Mix	DBA Rooms-inspired multi-mode reverb: ROOM / DIGIT / PEAK / GATE / WAVE / GONG. Freq and Depth are re-purposed per mode
Hydra	Div, Tempo, Fast, Slow, Tone, Mix	tempo-locked double-time and half-time ghost layers on one delay ring; built for drums
Spiral	Div, Tempo, Feedbk, Rise, Glide, Span, Tone, Mix	tempo-locked delay whose repeats climb or sink in pitch, compounding every repeat
Stasis	Length, Blur, Decay, Tone, Mix, Capture	footswitch-triggered freeze — the note you just played is held while you play over it. Capture selects stomp or explicit capture
Dustbox	Dust, Motor, Filter, Power	DOD FX33 Buzz Box-style fuzz with a flip-flop sub-octave — contributed, MIT
Rewire	Route, Bits, Drive, Ring, Comb, Shift, Tone, Mix	five lo-fi blocks — crush, drive, ring mod, comb, frequency shift — in a chain you can reorder. Shift is a true single-sideband shifter (−51 dB image), so it moves partials off the harmonic series
Gyre	Size, Feed, Decay, Rise, Glide, Span, Tone, Mix	granular feedback loop; two grains half a window apart with complementary windows, so the loop is unity-throughput and holds instead of running away
Galactic	Replace, Bright, Detune, Bigness, Mix	lush Airwindows reverb, wet path boosted for pedal levels
Oxide	Input, Tilt, Shape, Flutter, FlutSpd, Bias, HeadBmp, Output, Mix	Airwindows ToTape9 saturation. Input is a 0–4× drive compensated above unity, Tilt the Dolby-style encode/decode balance, Bias an asymmetric even-harmonic drive
Spool	Tempo, Div, Feed, Flutter, Wow, Wear, Drive, Spring, Mix	tempo-locked tape echo with flutter, wow, head wear, drive and a spring tail. Feed reaches self-oscillation above ~90

Every effect ends with a Mix knob (dry/wet, default 50), so levels and controls are consistent across the pack — an effect is audible as soon as it is selected. Dustbox is the exception; its fourth knob is Power.

The pedal can't hold or run all 22 at once (storage + DSP limits) — install a subset, back up first, and flash one at a time. Run heavy effects (Microlm, Galactic, Spool) one per patch.

Matujuice effects pack (included)

Twelve more effects, made by Luca Matturro (matujuice) on this project's toolchain and included here unmodified under his MIT licence: zoom-ms-zdl-effects-pack release v1.5. The files in dist/ match that release's checksums. v1.5 has its own Tempo knobs, so it runs on stock firmware; later releases (v1.6+) take their tempo from MIDISTOMP and are on his page. His full guide and licence are in dist/matujuice/; in Patch Editor they are listed under his name. Screens below are his artwork, as the pedal shows it.

Effect	What it does
WaveFold	Wavefolder (a Buchla 259 fold curve).
DualShft	Tempo-synced dual pitch shifter.
Choral	Pitch-tracked choir.
EuGate	Euclidean rhythm gate.
DubSiren	Dub siren with tape echo.
SGNL	Broken digital line: glitches, dropouts, codec damage.
Scrub	Scrub through the last seconds, freeze where you stop.
GridDly	One tempo-synced delay with six engines.
SyncEQ	EQ that passes the bar sync on to the effects after it.
Breather	Tempo-synced pump with a reverb.
DirtBox	Distortion box for acid lines: seven classic pedal models, EQ, noise reducer.
Sweep	Phaser, flanger and filter in one.

Made for synths and drum machines as much as guitar. Their IDs are 480 and 485-496. If you installed a very early Howl build (ID 480), reinstall Howl from dist/ before adding DualShft.

A looper and live screens

These run on the stock MS-70CDR firmware and are in dist/, tested on the pedal (2026-10-20). Their screens need firmware 2.10; on any other firmware they keep working as audio effects, and the screen effects simply pass the sound through. The live screens use the whole display: their knobs are on the pedal's knob pages, as usual.

Effect	What it does
Loop	A looper on the footswitch: record, play, overdub, stop, clear, with undo/redo. About 5 s, or about 23 s in experimental Long mode. Tempo quantize (set the BPM and beats per bar; the loop snaps to whole bars) with a click. Its screen shows the state, the time or bar and beat, and the loop's waveform.
Scope	A live oscilloscope of your signal, full screen: waveform, or XY (left against right).
Spectrum	A live spectrum analyzer, 40 Hz – 16 kHz, with peak hold, full screen.
Ring	A rotating ring that follows the signal, full screen.
Skull	A shaded 3D skull that reacts to your playing, idles with animations when you stop, and explodes at the loudest peaks.

Loop's Long mode (extra RAM) is still experimental; see its README. How an effect can animate its own screen is in animated-covers.md, built on Alexander Lim's (Leemuzhko) firmware notes.

Download Effects

The ready-to-load effects are in dist/. Point Zoom Effect Manager at that folder, or download individual .ZDL files from it. You do not need the build toolchain unless you want to modify or rebuild effects.

Install With Zoom Effect Manager

Use Zoom Effect Manager 2.3.3 or newer.

1. Open Zoom Effect Manager, connect your pedal, then open Settings.
2. Choose Read Effects from folder and select this repo's dist/ folder.

3. In the effect browser, enable Effects from devices and From Folder.
4. Add the desired effects to the device and write them with Zoom Effect Manager.

Back up your current effect list before writing. Experimental builds can freeze a pedal until power-cycled.

Effects must be installed with Zoom Effect Manager first. The patch editor only references effects by id — it cannot install them. Its dropdown is the full catalogue from every MS/G1/B1 model, not the subset on your pedal, so selecting something Effect Manager has never written leaves that slot blank. The editor warns when you pick an effect it has not seen in any of your patches, and tells you if the pedal drops one after a write.

If the effect browser says "No data to display, check filters": step 3 is not optional -- choosing the folder only tells Effect Manager where to look, and the browser's From Folder source has to be ticked separately. Connect the pedal before launching, and check no category filter is set (everything here is in Delay). If it still shows nothing, verify the files really are ZDLs and not saved HTML pages -- see docs/INSTALLING-ZDLS.md.

Gotchas learned the hard way:

• Effect Manager does not replace an installed effect with the same fxid — remove the old one from the device, re-read the folder, then add the new one.
• Effect Manager reads custom thumbnails from matching PNG files beside the ZDLs (for example, Rooms.ZDL and Rooms.png). Keep both files together and restart Effect Manager after updating them. These thumbnails use the same artwork as the pedal. PNG files are for the manager; they are not installed on the pedal.
• FS.bin size mismatch when writing = too many effects installed (storage overflow). DSP full = the per-patch processing budget is blown — run heavy effects (Microloom, Galactic, Spool) one per patch.
• If the pedal freezes on the boot screen (a patch references a bad effect): power off, hold the Parameter 1 (leftmost) knob pressed in, power on → All INITIALIZE → press the footswitch. Patches reset to factory, but effect binaries stay installed — then remove the bad one.

More detailed install notes live in docs/INSTALLING-ZDLS.md.

Compatibility

Device family	Status
Zoom MS-70CDR firmware 2.10	Primary hardware target; the release effects are developed and play-tested against this pedal.
Zoom MS-50G firmware 3.10	NAM (full rate and Eco) and CabIR confirmed by a user (#5). Patch Editor writes passed the opt-in write test on that pedal; still experimental. Same DSP headroom as the MS-70CDR.
Other ZDL-based Zoom pedals (MS-60B, G1on/G1Xon, B1on/B1Xon)	Compatible family, awaiting confirmation — hardware reports welcome.
Zoom MS-100BT	Custom effects confirmed by a user, installed over Bluetooth with third-party tools (#4). No USB MIDI, so no Effect Manager or Patch Editor. NAM/CabIR untested.
Original G3/G3X, G5, B3 and A3	Share the ZFX-IV DSP family, but this project's custom effects and Patch Editor are not currently supported or validated on them.
Newer Zoom ZD2-based pedals (Plus models; G1/G1X, B1/B1X and A1/A1X Four; G3n, G5n, B3n, AC-2/AC-3)	Not supported by these ZDL builds. ZD2 and ZDL effects are not interchangeable (Zoom Firmware Editor lists which pedal uses which; the A1 Four is assumed ZD2 like the rest of the Four series).

Does sharing the processor mean my pedal can run these effects? It makes porting worth investigating, but does not establish compatibility. Zoom's ZFX-IV name identifies a DSP family; it does not establish identical chip revisions, memory or clock speeds across every model. Installing custom effects also depends on the pedal's firmware and effect format, while Patch Editor support depends on its MIDI messages and patch layout.

Sources for the shared DSP family:

• G3/G3X, G5, B3 and A3: Zoom explicitly identifies ZFX-IV in its 2015 effects catalogue. The G3/G3X operation manual also confirms it. These are the original models, not the later G3n/G3Xn, G5n or B3n.
• MS-50G and MS-60B: a community motherboard comparison during a rehousing reports ZFX-IV markings on both boards. This is hardware evidence, not a confirmation that our effects or editor have been tested on both pedals.

The "+" models (MS-50G+, MS-60B+, MS-70CDR+) use ZD2, not ZDL, so nothing in dist/ loads on them. Custom ZD2 effects are now demonstrated on the MS-70CDR+ by Stomphacks, including a C-to-ZD2 build pipeline. Our pack and Patch Editor have not been ported. For NAM captures on a "+" pedal, nam2zoom works today (MS-50G+ and MS-70CDR+ tested, MS-60B+ experimental). See ZD2 research notes for the evidence, remaining memory/interface questions, and proposed next steps.

Step-by-step guide: docs/PROBING-A-NEW-PEDAL.md. Two things anyone with a "+" pedal can check, neither of which risks the hardware:

• python3 build/inspect_zd2.py Effect.ZD2 — reports entropy and structure. Uneven per-block entropy means plain code; flat and high everywhere means encrypted or compressed. Validated against a known-plain ZDL, random bytes and a gzip stream.
• Open the patch editor and click Connect. It reads the identity reply, adopts the device id so dumps are addressed correctly, and switches to READ-ONLY on any model but the MS-70CDR — every byte offset here was mapped against that one pedal, so writing elsewhere would scramble patches. If a "+" pedal answers Reload bank with a patch dump, that alone is worth reporting.

A working ZD2 build and USB-MIDI installation path has been demonstrated by Stomphacks on the MS-70CDR+. Other models and our effects still require their own validation; readable ELF data alone does not prove install compatibility.

What We Learned (field notes)

Hard-won findings from getting these effects stable on real hardware. The deep versions live in docs/ and build/ABI.md.

The two confirmed freeze classes

1. Code→data relocations. Any static array referenced from the audio function (even static const float[]) forces a relocation and freezes the pedal at load. Bake tables as #define scalar literals or unrolled macro sums instead — they compile to immediates. A clean build prints .fardata: 0 bytes and Applied 0 .obj relocations; anything else is a red flag. (This froze Spool until its 64-tap FIR was unrolled.)
2. Unresolved runtime helpers. Any float division, integer / or %, or math-lib call (sinf, powf, …) emits a __c6xabi_* helper the loader can't resolve — the branch goes to address 0. Use polynomial sin/cos, Newton-iteration reciprocals, and bit-mask tricks instead of modulo. See docs/SAFE-DSP-RULES.md.

Memory and CPU budgets

• The host gives each effect instance a large state arena via ctx[3], hardware-probed to ≥705,536 bytes — Lush-class (512 KB) and Spool-class (545 KB) states load fine. Always bounds-check the descriptor and clear big buffers lazily in chunks.
• DSP cost is a float the effect declares in its descriptor (stock effects declare 11.6–128). The pedal sums it across the patch and refuses the patch with DSP full above a limit measured at 224.4–228.4. The linker defaults to 20.0; heavy effects set an honest value (LinkerConfig.dsp_cost) — NAM declares 194/177, CabIR 10. Declaring too little lets the firmware green-light a chain the DSP can't run: crackles, or a hang at patch load.
• File size cap: a ZDL over ~32 KB freezes the pedal at boot (largest proven: 32,126 bytes file, 29,576 bytes code+data; 30,336 froze). build/zdl_size_guard.py enforces it.

Parameters are hostile

• The proven knob path delivers normalized 0..1 floats (an earlier ×7.14 scaling assumption made every knob saturate at ~14% travel).
• Saved parameters now initialize at patch load. The former freeze came from absolute handler call targets that lacked relocation records; the linker now emits PC-relative calls. All 22 release effects enable the corrected init. MatProb and Rooms are hardware-confirmed in all six slots, across patch changes and power cycles with the editor disconnected. The remaining effects are built and statically checked, with hardware listening still pending. See docs/PARAM-INIT-INVESTIGATION.md.
• The editor retains live-parameter replay for slots 1–3 for compatibility with older installed binaries. It cannot identify the installed build from its effect ID alone. Slots 4–6 still lack live 0x31 edits; initialization and editor-side update behavior are separate concerns.
• Refocusing an effect in the chain UI clobbers its param block with garbage until wiggled. The fix (piloted in Howl v3) is an edit-driven knob latch: a real knob turn changes one slot at a time, so bulk rewrites are detected and ignored, and the effect keeps sounding as dialed.
• Up to 9 params work (3 pages × 3), image shows the first three knobs; the multi-knob synthesized-handler path is hardware-proven.

Feedback DSP on this box

• Never feed a resonant filter back into itself — loop gain crosses unity almost everywhere. Use a pole-radius-controlled resonator (radius < 1 is unconditionally stable); that's how Howl works.
• A cubic soft-clip has 1.5× gain at small signal — inside a feedback loop that multiplies loop gain and self-oscillates. Use a unity-slope clipper (x − x³/6.75) in loops. (Caught twice: Scorch's output, then Dissolve's smear loop.)

Covers, screens, thumbnails

• The on-device cover is the full 128×64, 1-bpp, column-major in eight 8-row blocks, run-length encoded. The firmware paints live 20×15 knob-value boxes on top at coordinates the ZDL declares — so draw labeled dials under them, stock-style (build/decode_picture.py decodes any ZDL's cover; ~130 stock covers were decoded to learn this).
• The LCD pixels are ~1.3× taller than wide: pre-compress artwork vertically or circles render as tall ellipses.
• Hand-drawn covers: tools/cover_editor.html is a self-contained pixel editor with a device-aspect preview; exported JSON in src/airwindows/common/covers/ overrides the generated cover at build time.

Identity and packaging

• ZDL basenames must be ≤ 8 characters and unique after truncation, or effect identities collide and the pedal freezes at boot. The effect DB build refuses a dist/ that breaks this.
• There is no sort field in the header — on-device browse order tracks fxid. This pack uses 450+ to avoid stock collisions.
• gid ↔ category must match the exported symbol prefix (1=DYN, 2=FLT, 3=DRV, 6=CHO/MOD, 8=DLY, 9=REV); everything here is gid 8 (Fx_DLY_*) so the pack lives together in the least crowded menu.
• Reserved effect IDs (Delay group; FXIDs go up to 1023): this pack 403–499 and 914 (Spool), NAM captures 900–907, 950–957 and 500–699, CabIR cabs 930–945 and 700–899. Other projects building effects for these pedals: please avoid them. 409 is retired: Spool and TEcho4 (another collection) both used it, and swapping them froze a pedal at boot. An effect is identified by its group and ID together: Zoom's own effects reuse IDs across groups (DELAY, COMP, LINESEL, TREMOLO and HDHALL are all ID 8), and Skull (Delay 416) runs beside SpaceHole (Reverb 416). So a new Delay effect needs an ID no other collection uses in the Delay group (repeat98's registry lists them).

Build Your Own Effects

Start from a small effect in src/custom/ (e.g. reel or klang). Copy the directory, give the effect a new name and an unused fxid in manifest_pedal.json, update the C audio function and build.py, then add it to build_all.py.

Keep the first hardware test boring: audio_nop: true or tiny pass-through DSP, no static arrays, no divides, magic shuttle preserved. The safe path is docs/SAFE-DSP-RULES.md; effect directory conventions are in src/airwindows/README.md.

Build From Source

Zoom's and TI's files (stock effects, firmware, the stock handler blobs the linker uses, TI's manuals) are not in this repository; see STOCK-FILES.md for what a build needs locally.

Building requires Python 3.10+ and the TI C6000 Code Generation Tools (v8.5.0). Installing prebuilt effects from dist/ does not.

The build scripts expect the TI compiler here (edit TI_ROOT in the per-effect build.py if yours differs):

/Applications/ti/ti-cgt-c6000_8.5.0.LTS

python3 -B build_all.py            # all 22 release effects, with load initialization -> dist/
python3 -B build_all.py taffy      # one effect
python3 -B build_all.py --all      # + diagnostic/probe builds (-> build/probes/)

build_all.py also re-extracts the patch editor's inline effect database at the end, so the editor cannot go stale against dist/. It silently did, twice.

Desktop listening previews for the originals (no compiler, no pedal) are in tools/audio_preview/README.md.

Testing without a pedal

There is a headless C674x emulator (Ziddle) that runs these ZDLs, plus a test rig in tools/emulator/ that reports whether _init completes and whether params materialized. It is authoritative about instruction semantics and cannot see firmware readiness — it passed four _init builds that froze the pedal. Setup and limits: docs/EMULATOR-TESTING.md.

build/disassemble_zdl.py disassembles any ZDL, ours or one of Zoom's ~830 stock effects in stock_zdls/ (kept locally: STOCK-FILES.md). Diffing a generated handler against the stock equivalent has been the most productive debugging tool in the project.

Technical Notes

This repo builds loadable Zoom .ZDL effects without Zoom's unreleased SDK:

Path	Purpose
build/linker.py	Static linker: TI C6000 .obj → complete Zoom .ZDL (header, descriptor table, image info, edit handlers).
build/decode_picture.py	Decode any ZDL's on-device cover + knob-box layout back to pixels/PNG.
tools/cover_editor.html	Browser pixel editor for covers, with device-aspect preview.
tools/patch_editor.html	Web MIDI patch editor that sees custom effects (names/params extracted from the ZDLs; other editors only know stock). Serve the repo root over http://localhost and open it.
tools/editor.html	The same editor in Modwerk's design (open): it loads patch_editor.html and runs it under its own layout and styles, so features and fixes land in both. In testing; the classic editor stays the default.
build/extract_effect_db.py	Regenerate the patch editor's effect database from dist/ + stock ZDLs.
src/custom/	Original effects.
src/airwindows/	Airwindows-derived ports.
src/hardware_probes/	Diagnostic ZDLs used to map the pedal runtime ABI.
dist/	Release .ZDL files; never probes.
stock_zdls/	Zoom's stock effects, used for comparison and layout ground truth. Kept locally, not in the repository (STOCK-FILES.md).

Known runtime map for custom ZDLs:

Field	Meaning
ctx[1]	parameter float table
ctx[4]	dry/guitar input buffer
ctx[5]	current effect buffer, 8 left samples then 8 right samples
ctx[6]	output accumulator for effects that add instead of processing in place
ctx[11] / ctx[12]	magic shuttle; preserve every audio call
ctx[2] + 0x10 / ctx[2] + 0x18	small persistent per-instance state blocks
ctx[3][0..2]	large per-instance descriptor: base, end, byte span (≥705,536 B)

Repository Layout

ZoomMultistompZDL/
├── README.md
├── build/                 linker, ELF/ZDL helpers, cover decoder, handler blobs
├── docs/                  install notes, ABI status, and porting guidance
├── dist/                  release ZDLs to load in Zoom Effect Manager
├── graphics/              gallery renders of the on-device covers
├── tools/                 cover editor + desktop audio preview
├── src/custom/            original effects
├── src/airwindows/        Airwindows-derived ports + shared helpers
├── src/hardware_probes/   diagnostic ZDLs for runtime ABI experiments
├── stock_zdls/            tracked stock ZDL corpus used for comparison
└── build_all.py           release/probe build entrypoint

Several research references are useful locally but intentionally git-ignored: airwindows-ref/, zoom-fx-modding-ref/, ZoomPedalFun-main/. If you clone them beside the repo, treat them as read-only references.

Documentation

Doc	What it covers
CHANGELOG.md	What changed, newest first.
HANDOFF.md	Start here if you are picking this project up: current state, how to test, and what has already been ruled out.
docs/PARAM-INIT-INVESTIGATION.md	How the param-materialization bug was actually diagnosed — unrelocated absolute call targets — and the firmware tracing behind it.
docs/RELEASE-INIT-AUDIT.md	Rolling the fix out across all 22 effects, plus four follow-up defects found in the audit.
docs/INIT-MATERIALIZATION.md	Investigation record for the same bug, including four _init attempts that froze the pedal and the reasoning that went wrong.
docs/EMULATOR-TESTING.md	Running ZDLs headlessly against an emulated C674x, and the firmware behaviour it cannot see.
docs/EDIT-HANDLER-ABI.md	How generated edit handlers work, and why they delegate to ctx[7].
docs/MIDI-PARAM-EDIT.md	SysEx protocol for live param edits; the slots 1–3 rule.
docs/LOADER-SAFETY.md	Catalogued freeze causes mapped to their triggers.
docs/INSTALLING-ZDLS.md	Step-by-step Zoom Effect Manager folder install.
docs/SAFE-DSP-RULES.md	Pedal-safe DSP/linking constraints learned from hardware failures.
docs/ZDL-REVERSE-ENGINEERING-STATUS.md	Current map of the ZDL wrapper, runtime ABI, and known state fields.
docs/STATE-ABI-PROGRESS.md	Hardware-proven state/edit-handler findings.
docs/AIRWINDOWS-EXACT-PORTS.md	Rules for what can and cannot be called a 1:1 Airwindows port.
docs/CONTRIBUTING.md	Hardware-test asks and contribution notes.
build/ABI.md	Low-level linker/runtime ABI reference for developers.
docs/TI-PDF-NOTES.md + TI PDFs	TI C6000 toolchain references.
docs/pedal-research/	What's known about every other Zoom pedal people ask about: effect format, install path, IDs, risks and the next safe experiment.
docs/PROBING-A-NEW-PEDAL.md	How to find out whether a pedal this project has never seen — the + models especially — is analysable, talks MIDI, and hands over patches.

Related projects

Project	What it is
MS StompCtrl	Browser-only patch editor and backup tool for the MS-100BT, over Bluetooth in Chrome (open it). Reads, edits and writes patches, backs up the bank, and installs .ZDL files. A user has run four of this repo's effects on the MS-100BT (#4); back up first and report what you find. MIT.
MIDISTOMP	Custom firmware for the original MultiStomps: MIDI Program Change, CC control of every knob, MIDI clock with Start/Stop, a tap-tempo screen and footswitch-hold options. Installed by flashing a modified Zoom updater (riskier than an Effect Manager install). Tested on an MS-60B running MS-50G 3.10; MS-50G and MS-70CDR untested. MIT.
Matujuice ZDL effects pack	Luca Matturro's custom effects, built on this toolchain, made for synths and drum machines. v1.5 is included here; v1.6 and later follow MIDISTOMP's tempo (120 BPM on stock firmware). MIT.
repeat98/ZoomMultistompZDL	The upstream ZDL toolchain this fork started from.
nam2zoom	NAM captures on the Plus pedals (MS-50G+, MS-70CDR+; MS-60B+ experimental): one to ten captures in one "N2Z Bank" effect (Model, Bass, Mid, Treble, Vol, Input, Mix), on a smaller 14-layer network, with an optional cab IR. Windows app; macOS in preview. By Aleksandar Vukasinovic, MIT.
Leemuzhko/ZOOM_development	Alexander Lim's SDK notes and hardware results for the MS-70CDR. Much here rests on them: how an effect draws its own screen (the live screens and the zvis kit), the pedal's file-size cap and DSP limit, and linker pitfalls. The repo has no licence, so its findings are used here with credit, not its code.
Leemuzhko/HYBRID-IR	Alexander Lim's short-filter-plus-EQ cab idea behind CabIR.
Ziddle	C674x emulator used to test ZDLs before they touch hardware.
r/zoommultistomp	Community subreddit for the MultiStomp pedals.

Contributing

Hardware reports are gold. When testing a ZDL, please include:

Item	Example
Pedal model and firmware	MS-70CDR firmware 2.10
ZDL filename and commit	Taffy.ZDL @ 864d85d
Load result	boots, freezes on startup, freezes on unbypass
Audio result	bypass, dry passthrough, effect works, high-pitched tone
Parameter behavior	Speed works 0..100, Chance saturates, page 2 knob missing

Open an issue or PR with findings. Keep experimental claims precise: "boots on my MS-70CDR" is more useful than "works everywhere."

License

Everything in this repository is MIT; see LICENSE:

• This fork's own work (the custom effects in src/custom/, the browser tools in tools/, the notes in docs/, the cover art in graphics/): MIT, Roman Rusinov.
• The upstream toolchain this is forked from, repeat98/ZoomMultistompZDL (the linker, the ZDL tools, the ABI and reverse-engineering notes, the first effects): MIT, Jannik Assfalg.
• Airwindows DSP in src/airwindows/: MIT, Chris Johnson/Airwindows, under its own terms.
• The Matujuice effects in dist/ (Breather, Choral, DirtBox, DualShft, DubSiren, EuGate, GridDly, SGNL, Scrub, Sweep, SyncEQ, WaveFold) and the renders of their screens in graphics/ and the effects overview: MIT, Luca Matturro; his licence is in dist/matujuice/LICENSE.

Zoom's firmware and stock effects and TI's toolchain and manuals belong to Zoom Corporation and Texas Instruments. They are used locally for interoperability and reverse-engineering research and are not in this repository (STOCK-FILES.md). One exception is being worked on: the built effects still carry knob-handler code derived from a stock Zoom effect, which will be replaced with handlers of our own.

Not affiliated with or endorsed by Zoom Corporation. Flashing custom effects is at your own risk.