Slammer

A three-layer synthesized kick drum plugin with a parallel 909-style clap voice. SUB sine, MID sine+noise, and a band-passed click TOP mix into a five-voice distortion palette, a tilt/low/notch master EQ, and a full master bus (RMS compressor → transformer drive → brickwall limiter → auto tube warmth). Ships with a 16-step pattern sequencer, a factory

• user preset browser, one-shot WAV/AIFF bounce, and a fully interactive standalone editor.

Formats: VST3, CLAP, Standalone Platforms: Linux, macOS (Apple Silicon + Intel), Windows License: GPL-3.0-or-later

Listen

▶ Play sound samples in your browser

Ten one-shots bounced straight out of the plugin via the BOUNCE button — clean kicks, 808/909 emulations, claps, snares, toms, and hats. No download, just hit play.

Quick start

Download the latest build for your platform from the Releases page, extract, and run the installer:

# Linux / macOS
./install.sh

# Windows (run as Administrator)
install.bat

Rescan plugins in your DAW. Slammer appears as Hyperfocus DSP / Slammer.

Download

Platform	File
Linux x86_64	slammer-linux-x86_64.tar.gz
macOS ARM (Apple Silicon)	slammer-macos-arm64.tar.gz
macOS Intel	slammer-macos-x86_64.tar.gz
Windows x86_64	slammer-windows-x86_64.zip

Each archive contains the standalone binary, VST3 and CLAP plugin bundles, and an install script.

Verify your download

Every release ships a SHA256SUMS.txt file on the Releases page. Download it alongside the archive and verify before running:

# Linux / macOS
sha256sum -c SHA256SUMS.txt

# Windows (PowerShell)
Get-Content SHA256SUMS.txt | ForEach-Object {
  $hash, $file = $_ -split '\s+'
  $actual = (Get-FileHash $file -Algorithm SHA256).Hash.ToLower()
  if ($actual -eq $hash) { "$file OK" } else { "$file FAILED" }
}

You can also upload the archive to VirusTotal for a third-party scan before running — slammer is unsigned open-source software, so extra caution is welcome.

macOS setup — step by step

The binaries are not codesigned or notarized, so macOS will block them on first launch. Here's the complete boomer-friendly walkthrough:

1. Extract the archive

Double-click the .tar.gz file in Finder — macOS extracts it automatically into a folder next to the archive. Or, if you prefer Terminal:

cd ~/Downloads
tar xzf slammer-macos-arm64.tar.gz
cd slammer-macos-arm64

2. Remove the quarantine flag

macOS marks every downloaded file as untrusted. You need to clear that flag on everything inside the extracted folder. Open Terminal, cd into the folder, and run:

xattr -dr com.apple.quarantine .

(The dot at the end is important — it means "this folder and everything in it".)

3. Run the standalone

Use the included launch script — it configures the audio buffer size so CoreAudio plays nicely with nih-plug's backend:

./slammer-macos.sh

If macOS still blocks the binary after you've removed the quarantine flag, open System Settings → Privacy & Security, scroll to the bottom, and click Open Anyway next to the Slammer warning. You only need to do this once; future launches will go straight through.

4. Install the plugins for your DAW

Copy the VST3 and CLAP bundles into the standard macOS plugin locations:

cp -r slammer.vst3 ~/Library/Audio/Plug-Ins/VST3/
cp -r slammer.clap ~/Library/Audio/Plug-Ins/CLAP/

Then rescan plugins in your DAW.

Note on the launch script: slammer-macos.sh starts the standalone with --period-size 4096 to work around a CoreAudio variable-buffer issue in nih-plug's CPAL backend (upstream bug). This adds slight latency in standalone mode only. VST3 and CLAP running inside a DAW are unaffected.

Audio Unit (AU) is not supported. Most macOS DAWs (Ableton Live, Bitwig, REAPER, Renoise, FL Studio) support VST3 or CLAP. Logic Pro is AU-only and will not see Slammer.

Features

Signal chain

SUB + MID + TOP voices  (+ parallel CLAP voice)
  → per-voice saturation (5-mode palette)
  → master EQ (tilt / low shelf / notch)
  → master bus (RMS comp → transformer drive → brickwall limiter)
  → auto tube warmth (engages above 0 dB master)
  → master volume → out

DSP

• Three-layer kick engine — SUB sine with pitch envelope, MID sine+noise blend, TOP bandpass-filtered click transient. Each layer has independent tuning, amp + pitch envelopes, and drift.
• 909-style CLAP layer — parallel voice, white noise → 2-pole SVF bandpass → baked 3-burst + exponential tail envelope. Tunable independently of the kick (level, center frequency 500–5000 Hz, tail 50–400 ms). Toggleable; bit-identical bypass when off.
• Five-voice distortion palette — each mode is a genuinely different curve, not just gain+tanh:
  • Sat Clip — split-band rational hard-shoulder (x/√(1+x²)) with a 60 Hz low-pass bypass that keeps the sub clean.
  • Sat Diode — asymmetric exponential pair.
  • Sat Tape — drive-reactive low-pass plus hysteresis memory; the only mode with dynamic/frequency-dependent behavior.
  • Transformer drive (master bus) — polynomial 2nd+3rd harmonic blend with a feed-forward 60 Hz "bloom" filter.
  • Master warmth — asymmetric cubic bias shaper that auto-engages above 0 dB master volume; bit-exact bypass below unity.
• Master bus compressor — three macros (Amount, Reaction, Transformer drive) for fast moves, plus a precision strip with independent Attack (0.3–50 ms), Release (20–800 ms), and soft Knee (0–12 dB, Reiss & McPherson quadratic). Brickwall limiter LED, GR meter. RCT acts as a link macro — moving it writes Attack and Release together via the host parameter API. Knee = 0 is bit-identical to a hard-knee path.
• Master EQ — tilt, low shelf, and variable-Q notch.
• One-shot bounce — render the current sound with the full chain to a 16-bit / 44.1 kHz WAV or AIFF via a dedicated BOUNCE button. Runs offline on the GUI thread against a fresh DSP instance, so live audio keeps flowing during the render and the result is bit-for-bit reproducible.

UI

• Single-window editor — 680 × 444 rack panel with aspect-ratio locked scaling; resize the DAW window and the UI scales without distortion.
• Header preset bar — 7-segment LED display, dropdown browser, inline rename (double-click to edit), save, delete. Up/Down arrow keys cycle presets. Factory presets are protected from deletion.
• 16-step pattern sequencer — four-on-the-floor default, click or drag to paint steps. Runs standalone with internal transport, or locks to host tempo and transport inside a DAW.
• Interactive tempo entry (standalone only) — single-click the BPM readout to arm, drag vertically to scrub, double-click to type a value, or use Left/Right arrows (±10, Shift for ±1). Host-synced mode keeps the readout read-only.
• Waveform scope — live output waveform display fed post-comp, so the trace visibly shrinks under compression and caps under the limiter. GR meter sits next to it.
• Test trigger — press T anywhere in the editor to fire a kick without MIDI.
• BOUNCE button — one click renders a single hit, opens a native save dialog (remembered between bounces), writes WAV or AIFF.

Persistence

• Factory + user presets — stored as forward-compatible JSON with #[serde(default)] on every field, so new parameters in later versions won't break existing files.
• Last preset recall (standalone) — the editor remembers the last loaded preset and restores it on next launch.
• DAW state — full parameter + sequencer pattern persistence inside DAW project files.

Controls

Input	Action
T key	Fire a test kick
MIDI NoteOn	Trigger the engine (velocity → VEL knob)
BOUNCE button	Render current sound to WAV / AIFF
Click + vertical drag	Adjust any knob
Shift + drag	Fine control
Ctrl + click (knob)	Reset knob to default
Double-click (knob)	Reset to default
Arrow Up / Down	Cycle presets (prev / next)
Arrow Left / Right	Tempo ±10 BPM (when tempo armed)
Shift + Left / Right	Tempo ±1 BPM (when tempo armed)
Space	Play / stop sequencer (standalone only)
Click on BPM readout	Arm tempo widget
Double-click BPM readout	Enter tempo value by keyboard

Preset and log locations

Resolved via the directories crate — correct on every platform:

Platform	Presets	Logs
Linux	~/.local/share/slammer/presets/	~/.local/share/slammer/slammer.log
macOS	~/Library/Application Support/Slammer/presets/	~/Library/Application Support/Slammer/slammer.log
Windows	%APPDATA%\Slammer\slammer\data\presets\	%APPDATA%\Slammer\slammer\data\slammer.log

Building from source

Prerequisites

Rust (stable, 1.75+):

curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

System dependencies (Linux only — macOS and Windows need nothing extra beyond Rust):

Debian / Ubuntu / Pop!_OS

sudo apt update
sudo apt install build-essential pkg-config cmake \
    libx11-dev libx11-xcb-dev libxcb1-dev libxcb-icccm4-dev libxcb-keysyms1-dev \
    libxcursor-dev libxkbcommon-dev libgl-dev libasound2-dev libjack-dev

Arch Linux / Manjaro

sudo pacman -S --needed base-devel pkg-config cmake \
    libx11 libxcb xcb-util xcb-util-wm xcb-util-keysyms \
    libxcursor libxkbcommon mesa alsa-lib jack2

Build

git clone https://github.com/hyperfocusdsp/slammer.git
cd slammer

# Standalone only (quick dev loop)
cargo run --release --bin slammer-standalone

# Full plugin bundles → target/bundled/slammer.{vst3,clap}
cargo xtask bundle slammer --release

The project is pinned to a specific nih-plug commit for reproducible builds — see Cargo.toml for the current SHA.

Development

cargo test                                  # DSP unit tests
cargo clippy --all-targets -- -D warnings   # lint gate used by CI
cargo fmt                                   # rustfmt

Project layout

src/
├── lib.rs              crate root + nih_plug exports
├── main.rs             thin standalone wrapper
├── plugin.rs           Plugin impl: process(), editor(), MIDI
├── params.rs           SlammerParams + ParamSnapshot (preset round-trip)
├── presets.rs          factory presets + user preset I/O
├── sequencer.rs        16-step atomic sequencer (audio↔GUI via atomics)
├── logging.rs          tracing subscriber + log rotation
│
├── dsp/
│   ├── engine.rs       KickEngine: three-layer mix, master EQ
│   ├── oscillator.rs   band-limited sine
│   ├── envelope.rs     pitch + amp envelopes
│   ├── noise.rs        colored noise generator
│   ├── click.rs        pre-rendered bandpass click buffer
│   ├── clap.rs         909-style parallel clap voice (bandpass + 3-burst env)
│   ├── drift.rs        per-trigger analog-style pitch jitter
│   ├── filter.rs       biquad + master EQ chain
│   ├── saturation.rs   five-voice distortion palette (pre-EQ)
│   ├── master_bus.rs   RMS comp (macro + precise) + transformer drive + limiter
│   └── tube.rs         auto master warmth (post-bus, pre master-vol)
│
├── export/
│   ├── mod.rs          BOUNCE entry point + remembered-path config
│   ├── render.rs       offline one-shot render mirroring the live chain
│   └── writer.rs       16-bit WAV (hound) + AIFF writers
│
├── ui/
│   ├── editor.rs       top-level egui shell
│   ├── panels.rs       layout: header, master row, layer rows, sequencer
│   ├── preset_bar.rs   preset LED display + dropdown + save/delete
│   ├── seven_seg.rs    7-segment LED rendering
│   ├── knob.rs         industrial knob widget
│   ├── widgets.rs      shared drawing primitives (groove, LED, rack ear)
│   └── theme.rs        colors, fonts, spacing
│
└── util/
    ├── paths.rs        cross-platform data/preset/log directories
    ├── telemetry.rs    lock-free audio→UI peak ring buffer
    └── messages.rs     lock-free UI→audio command queue

Known limitations

• No Audio Unit (AU) support — nih-plug limitation; use VST3 or CLAP.
• Window scaling — aspect ratio is locked, but the window is not free-form resizable (egui-baseview limitation). Host window size snaps to the nearest integer multiple of the 680×444 base layout.
• Standalone on macOS Apple Silicon — requires the included slammer-macos.sh launch script to set --period-size 4096. VST3 and CLAP inside a DAW are unaffected.

Dependencies

Built with nih-plug (plugin framework), egui (GUI), parking_lot (locks), rtrb (lock-free ring buffer), and directories (cross-platform paths). See Cargo.toml for the full list.

License

GPL-3.0-or-later. See LICENSE for the full text.