Bus Channel Strip is a single plugin that replaces eight inserts on your master or stem bus. Load it once and run your mix through a console EQ, an Airwindows glue compressor, a passive tube EQ, a dynamic EQ with sidechain support, a vintage transformer stage, a psychoacoustic stereo widener, a transparent loudness maximizer, and a hidden master-end polish coat — in that order, or in any order you like (the first seven are reorderable; the polish coat is pinned at the end).

Every module is individually bypassable and fully automatable. Every parameter reads as a clean integer in your DAW's automation lanes. The signal chain has a global bypass for zero-latency passthrough and RMS-based Auto Gain compensation so level differences don't fool your ears when you're comparing.

Go to Releases and grab the archive for your platform:

Install paths:

macOS Intel note: The Intel build ships without the GUI (Skia cross-compile limitation on Apple Silicon runners). All DSP is present and functional; use the ARM64 build if you need the visual interface.

Two major workstreams ship together: Sheen (a hidden master-end polish coat) and a full multi-fx rack UX redesign that finally makes module reordering feel native.

A new pinned DSP stage at the end of the chain (post-Punch, pre-master-gain) that makes the chassis sound finished out of the box. The brushed-brass API brand plate in the chassis header is the only front-panel surface — click it to flip into a hidden back view with five sliders. Always-on by default at research-grounded factory tuning:

Defaults are anchored in three parallel research reports — classic console-bus measurements (SSL G, Neve 33609, API 2500, Studer, Trident), polish-plugin teardowns (Slate Revival, Kush AR-1, Maag EQ4, Sonnox Inflator, Pensado, Vitamin, Ozone, PSP Vintage Warmer, bx_console), and tape + transformer harmonic profiles (Studer A800, Ampex ATR-102, Jensen, Lundahl, Carnhill). See docs/SHEEN_MODULE_SPEC.md for citations and stage-by-stage rationale. Excluded from Auto Gain — auto-comp on a polish stage defeats its purpose.

The seven-slot rack got a ground-up UX overhaul:

• Native vizia drag-drop replaces the previous hand-rolled mouse-capture state machine that was silently failing under baseview's Win32 SetCapture lifecycle.
• Swap-or-insert semantics decided by cursor X within the target slot at release time: left third = insert before, middle = swap, right third = insert after.
• Live drop-position preview while dragging — bright cyan bar pinned to the target slot's left or right edge (insert) or full yellow ring around the slot (swap), so you see the resolved drop intent before releasing.
• Floating drag-ghost label tracks the cursor showing the dragged module's tag.
• Empty slots collapse by default to narrow dashed tabs; the library sidebar is now the sole "add module" affordance.
• Focus mode — press 1..7 to focus a real-module slot (collapses every other slot to a tab); Esc exits focus, cancels drag, or closes any open back view.
• Chain mini-map appears as a band above the chassis only when a slot is focused, hidden otherwise.
• Brushed-brass brand plate is the entry point to the Sheen back view; mutually exclusive with the DynEQ back view.
• Click-lag fix — the chassis-level MouseUp listener that previously routed every click through the broken drag state machine has been removed.

11 new automation params (Sheen) on top of the existing ~75 — no reused IDs. Existing DAW sessions load with Sheen ON at factory defaults; playback will subtly differ from pre-1.0 sessions. For bit-identical playback, flip the back-panel master Sheen bypass.

Theme: "Stop sounding digital." A perceived-quality release targeting the four artifacts that read as "digital" to a trained ear — top-octave aliasing, midrange phase smear, lifeless memoryless saturation, and overly-precise stereo imaging. ~3-month scope. Full requirements in docs/V2_ROADMAP.md.

• Universal 4× internal oversampling across every module containing a nonlinearity (ButterComp2, Pultec tube saturation, Transformer, Sheen WARMTH). Punch oversampling normalized as a global quality preset.
• TPT (topology-preserving transform) state-variable filter cores replace biquad direct-form-1 in API5500, Pultec, DynamicEQ, and Sheen EQ stages — eliminates phase smear at extreme Q and cleanly accepts coefficient automation.
• Optional linear-phase mode on Pultec (mastering EQ) — windowed-sinc FIR with FFT convolution, ~512-sample latency at 4×.
• Single-cell Preisach hysteresis model in Transformer core + as an opt-in "tape" mode on Sheen WARMTH — gives saturation actual memory (output depends on input history, not just present input), which is what "lifeless" really means perceptually.
• Per-channel coefficient micro-detuning (TMT-style ±0.3%) on API5500, Pultec, Transformer, Sheen — produces natural stereo decorrelation rather than the unnaturally precise center image of identical L/R coefficients.
• ButterComp2 adaptive envelope — program-dependent attack curve that softens on transient-dense material (drum bus auto-softening, vocal bus auto-tightening).
• Punch true-peak detection (ITU-R BS.1770-4) with intersample peak metering and a -1 dBTP default ceiling.

• Resizable window (1100×750 to 2400×1400, locked aspect) with HiDPI awareness — currently locked at 1300×860.
• Preset system — 20 factory presets across genres (rock drum bus, pop vocal bus, hip-hop master, jazz acoustic, EDM master, podcast voice, classical orchestra, etc.), browser UI with categories, user save/load to ~/Documents/Bus Channel Strip/Presets/, current-preset name in chassis header with diff indicator.
• Per-module inline metering — tiny reactive spectrum strip atop each EQ module, consistent GR meters on compressors, saturation meters on Transformer / Punch / Sheen WARMTH.
• Visual polish pass — typography rhythm (12/14/16/20/24px scale), spacing rhythm (4/8/12/16/24px grid), knob spring-back micro-interactions, follow-cursor value tooltips during drag, custom SVG icon set replacing Unicode glyphs.
• Theming — ships with two curated themes (Studio dark, Daylight bright). User-customizable colors deferred to v2.1.
• Tooltips — hover any control >800ms for control name + one-sentence description (text lives in src/tooltips.rs).

• lib.rs refactor — extract per-module parameter definitions into a params/ module (forced by the preset system work).
• CI/CD fix — repair the macOS / Linux GitHub Actions builds that currently fail (forced by the signed-installer work).
• macOS code signing + notarization — required for "broader audience" distribution.
• Installer packages (Windows MSI, macOS pkg) replacing zip extraction.
• Test coverage expansion — every new DSP module tested at the same density as Sheen.

• Parameter IDs from v1.0 stay stable.
• TPT EQ migration is a breaking sound change — sessions saved in v1.0 will load and play in v2.0 but null within ~0.1 dB of the biquad versions at moderate settings, larger at extreme Q.
• Hysteresis on Transformer is a bigger sound change — a new transformer_hysteresis_bypass BoolParam (default OFF, i.e. hysteresis on) lets users flip back to v1.0 behavior for bit-identical playback.

A/B compare snapshots · MIDI parameter learn · multi-instance link · sidechain routing for non-DynEQ modules · new DSP modules · user-customizable theme colors · workflow features generally.

[API5500 EQ] -> [ButterComp2] -> [Pultec EQ] -> [Dynamic EQ] -> [Transformer] -> [Haas] -> [Punch] -> [Sheen]

The first seven modules occupy reorderable slots — drag any module's body to swap it with another slot, insert it before, or insert it after, with a live cyan/yellow drop indicator showing where it'll land. Sheen is pinned at the master end (post-Punch, pre-master-gain); it's the chassis-level "polish coat" exposed via the brushed-brass brand plate. Every module is individually bypassable. The chain is fully automatable — all ~86 parameters are exposed to your DAW.

• Global Bypass — Engages zero-latency passthrough for the entire chain (including Sheen). Use it for A/B comparisons at a glance.
• Auto Gain — RMS-based output compensation (~5 second time constant) that matches the processed and bypassed levels. Sheen is intentionally excluded from this calculation — auto-comp on a polish stage defeats its purpose.
• Module Reordering — Click and drag any reorderable slot's body to a new position. Drop in the left third of a target to insert before, the middle to swap, the right third to insert after. A live cyan bar (insert) or yellow ring (swap) shows the resolved drop intent before you release. Drop on an empty slot to move there. A floating ghost label tracks the cursor showing what you're moving.
• Focus Mode — Press 1..7 to focus a real-module slot (collapses every other slot to a tab so the focused module gets the full chassis width). Press Esc to exit.
• Brushed-Brass Plate — The "API Bus Channel Strip" brand mark in the chassis header is clickable; it opens the hidden Sheen back view. Mutually exclusive with the Dynamic EQ back view.

just check        # Fast type-check (no codegen)
just bundle       # Production VST3 + CLAP bundle with GUI
just deploy       # bundle + install to system plugin directories
just qa           # fmt-check + lint + test

set LLVM_HOME=C:\Program Files\LLVM
set LIBCLANG_PATH=C:\Program Files\LLVM\bin
cargo +nightly run --package xtask -- bundle bus_channel_strip --release --features "api5500,buttercomp2,pultec,transformer,punch,haas,dynamic_eq,sheen,gui"

Bundles output to target/bundled/.

Important: Do not set BINDGEN_EXTRA_CLANG_ARGS, CC, or CXX when building with the gui feature — they conflict with Skia's build system. Windows builds Skia from source; LLVM 19+ is required for MSVC STL compatibility.

just check        # Fast type-check
just build        # Debug build (no GUI)
just build-gui    # Debug build with GUI
just bundle       # Production VST3+CLAP bundle
just bundle-core  # Bundle without GUI (faster iteration)
just install      # Install to system plugin dirs
just deploy       # bundle + install
just test         # Unit tests
just lint         # Clippy -D warnings
just fmt          # nightly rustfmt
just qa           # fmt-check + lint + test
just env          # Show build environment

All process() paths are allocation-free, lock-free, panic-free, and I/O-free. No heap allocation, no mutexes, no .unwrap(), no file or system calls. Parameter communication between the GUI and the audio thread uses atomics only.

• Biquad filter coefficients update via update_coefficients() — no state reset on parameter changes
• ButterComp2 FFI is called once per buffer, not once per sample
• Dynamic EQ uses a 0.05 dB hysteresis gate on coefficient updates to skip trigonometric calls when the envelope is stable
• Transformer parameter caching gates update_frequency_response() to actual changes only
• Punch oversampling uses linear interpolation upsample and IIR downsample (pole = 0.05); transient shaping runs pre-clip to prevent pumping

• NIH-Plug — plugin framework (~86 parameters, VST3 + CLAP output)
• vizia-plug — GUI framework (Skia GPU backend, ECS reactive architecture); v1.0.0 uses vizia's native on_drag / on_drop API for rack drag-drop
• biquad 0.5.0 — filter implementations (routed through shaping::biquad_coeffs to work around the v0.5.0 frequency-normalization bug)
• Airwindows ButterComp2 — C++ FFI via extern "C" wrapper in cpp/
• realfft — FFT for the spectral analyzer

src/
  lib.rs           # Plugin entry, parameter definitions, process() dispatch (slot loop + Sheen tail)
  api5500.rs       # 5-band semi-parametric EQ
  buttercomp2.rs   # Airwindows ButterComp2 FFI wrapper
  pultec.rs        # Pultec EQP-1A tube EQ
  dynamic_eq.rs    # 4-band dynamic EQ
  transformer.rs   # Transformer saturation module
  haas.rs          # Psychoacoustic stereo widener (M/S + Haas comb)
  punch.rs         # Clipper + transient shaper with oversampling
  sheen.rs         # Pinned master-end polish coat (5 stages, default-on)
  editor.rs        # vizia GUI: chassis header + brass plate + library sidebar +
                   #   scrollable rack with native drag-drop / live drop preview /
                   #   floating ghost / focus mode / mini-map / DynEQ + Sheen back views
  components.rs    # Reusable GUI components
  spectral.rs      # FFT analysis + gain reduction metering
  shaping.rs       # DSP math utilities + biquad_coeffs workaround
  styles.rs        # vizia CSS-like styles (includes brass plate + Sheen back-view themes)

cpp/               # C++ Airwindows FFI wrappers
xtask/             # Build tooling (bundle, install)
docs/              # Documentation + GitHub Pages site (includes SHEEN_MODULE_SPEC.md
                   #   and MULTI_FX_UI_DESIGN.md)

Full control reference, genre signal chain examples, and preset descriptions:

fsecada01.github.io/bus_channel_strip

Internal design documents in docs/:

• SHEEN_MODULE_SPEC.md — Sheen DSP design with research citations and factory-default rationale
• MULTI_FX_UI_DESIGN.md — Rack UX design: consolidation pass + drag-drop redesign with hit-test semantics
• GUI_DESIGN.md — UI specifications and layout
• PUNCH_MODULE_SPEC.md — Punch DSP design and psychoacoustic research
• CLIPPING_INSIGHTS.md — Professional loudness techniques

GPL-3.0-or-later. See LICENSE.

Airwindows source code is copyright Chris Johnson, released under the MIT license.