M-QuadFade

Fwuzeem Audio M-Series

What it is

M-QuadFade is a 2D joystick-style four-bus stereo crossfader. It has four mandatory stereo input buses, A through D, and one mandatory stereo output. The XY pad sets four bilinear gains, so the plug-in morphs four stereo sources into one stereo result; it is not a stereo-input-to-four-output splitter in the current source.

For pad coordinates x and y, each in the range 0.0 to 1.0, the smooth weights are:

• A = (1-x) * (1-y)
• B = x * (1-y)
• C = (1-x) * y
• D = x * y

The four weights sum to 1.0 before the master gain stage.

Controls & parameters

XY pad

The four labelled pad corners are A top-left, B top-right, C bottom-left, and D bottom-right. At the default centre position, all four smooth weights are 0.25.

Mode and sub-mode

SMOOTH applies the bilinear weights multiplied by Master Gain. Master Shift is not used in this mode. There is no constant-power sine or cosine curve in the current implementation.

BITSHIFT replaces the continuous weights with exponent-quantised power-of-two gains, then applies Master Shift. In COARSE, the processor selects the nearest of 35 precomputed configurations: four single-bus corners, six two-bus edges, twelve three-bus configurations, one equal four-bus configuration, and twelve graded four-bus configurations. In FINE, each raw weight is mapped to an exponent and the resulting gains are normalised to a unity sum before Master Shift:

• weight >= 0.85 -> shift +2
• weight >= 0.60 -> shift +1
• weight >= 0.35 -> shift 0
• weight >= 0.15 -> shift -1
• otherwise -> shift -2

HYBRID follows the continuous bilinear path while the puck is moving. After 300 ms without XY movement it locks to the selected BITSHIFT quantisation. Moving the puck releases the lock and returns to the continuous path.

Master controls

The base Master Shift default is 0. When the editor changes to FINE it sets Master Shift to -2; when it changes back to COARSE it sets Master Shift to 0. Master Gain is disabled in BITSHIFT, and Master Shift is disabled in SMOOTH.

Meters and view detail

The A, B, C, and D meter bars show the effective smoothed gain for each input bus and its dB readout. In HYBRID, a ghost bar shows the continuous bilinear target while the main bar shows the quantised effective gain. The sum readout is available in the Standard and Full views.

The GUI detail selector has three levels: Simple, Standard, and Full. It defaults to Standard and is saved as editor state. Simple shows the pad and master knobs; Standard adds the meters and sum information; Full adds the mode and sub-mode buttons. It does not change the DSP.

Workflow / how to use it

1. Feed four stereo sources into buses A, B, C, and D. The host must provide all four stereo input buses and one stereo output bus.
2. Start in SMOOTH with the pad at the centre. Each bus contributes 0.25 at Master Gain 1.0.
3. Drag the puck toward a corner to favour that bus, or move along an edge to crossfade between the two buses on that edge. The pad position is continuously automatable through X Position and Y Position.
4. Adjust Master Gain when a linear overall level change is required. In SMOOTH, Master Shift is inactive.
5. Choose BITSHIFT for stepped power-of-two routing. Choose COARSE for the 35 curated configurations or FINE for per-bus exponent quantisation and unity normalisation.
6. Choose HYBRID when continuous movement should settle into a repeatable quantised state. Stop moving for 300 ms to lock; move again to return to the free path.
7. Watch the A-D meters for effective gain, quantised shift, dB level, and the Hybrid ghost target. Use Full view when the mode and sub-mode buttons are needed.

Use cases

DJ-style four-bus morphing

Place four stereo decks, stems, or effect returns on A-D and use the pad as a single two-axis morph control. Smooth mode gives continuous movement between the four sources; the four corners provide direct bus emphasis.

Ambient crossfades

Use slowly changing X and Y automation to move through the four-bus space while Smooth mode and its 5 ms gain ramps remove abrupt parameter steps. Master Gain can provide the overall linear level trim without changing the pad path.

Mastering A/B/C/D routing

Place four stereo versions of a source on A-D, such as alternate chains or revisions, then use the pad to audition pairwise edges and intermediate blends. The single stereo output feeds the monitoring or final mastering chain.

BITSHIFT law for exact power-of-two fades

Use BITSHIFT when a transition should be described as exponent steps rather than an arbitrary gain curve. COARSE provides the finite 35-state map; FINE quantises each bus to shifts from -2 through +2 and normalises the four-bus sum. Master Shift then applies an integer power-of-two multiplier across the result.

Specs & requirements

• Host layout: four mandatory stereo inputs, A through D, and one mandatory stereo output.
• Processing: zero reported plug-in latency and a zero-second reported tail.
• Gain transition smoothing: 0.005 s, or 5 ms, per bus.
• Formats: AU, VST3, and Standalone.
• Platform: macOS; the audio toolbox deployment target is macOS 10.15.
• MIDI: does not accept or produce MIDI.
• Identity: Fwuzeem Audio, manufacturer code Fwzm.

Notes & caveats

• M-QuadFade is a four-input-to-one-output mixer/crossfader in the current source. It does not split one stereo input into four output buses.
• SMOOTH is pure bilinear interpolation. The current implementation has no constant-power response option; the pre-master bilinear weights sum to 1.0.
• BITSHIFT uses the power-of-two law 2^shift with integer exponent steps. Master Gain is ignored by BITSHIFT; Master Shift is ignored by SMOOTH.
• HYBRID is continuous while moving and quantised after 300 ms of stillness. Its 5 ms gain ramps are smoothing, not plug-in latency.
• The current processor exposes a float processing path. The older README claim of native FP64 processing is not reflected in the live source.
• All four stereo input buses are required by the supported bus-layout check; a stereo-only host layout is not a substitute for the four-bus layout.