theallelectricsmartgrid

The Encoder System

The Smart Grid One relies entirely on a software-defined parameter system. All “knob” state lives in software, allowing for complete recall, deep modulation, macro control (gestures), and A/B scene morphing.

The core implementation spans private/src/Encoder.hpp, private/src/EncoderBank.hpp, and private/src/EncoderBankBank.hpp.

Ownership now lives in EncoderBankBank: it owns a flat array of BankedEncoderCell instances indexed by SmartGridOneEncoders::Param. Each EncoderBankInternal starts with null base cells and receives raw pointers through PlaceEncoder(...). This makes encoder swapping explicit and keeps base cells empty until they are placed.

Serialization follows ownership: EncoderBankBank::ToJSON() iterates the full encoder array and writes each named parameter, and FromJSON() does the inverse by looking up each name and updating the encoder state.

Base Structure: Tracks and Voices

To accommodate polyphony and quadraphonic effects, the parameter system is structured hierarchically.

Voices: The synthesizer engine runs 9 simultaneous voices. For quadraphonic effects (like the Quad Delay, Quad Reverb, and Partial Machine), there are 4 independent channels (effectively acting as voices in the parameter system).
Tracks: Voices are grouped into tracks. For example, the 9 voices are grouped into 3 trios. The parameter system addresses these as 3 tracks, with 3 voices per track.
Banks: Parameters are grouped into Banks (e.g., “Source”, “Filter”, “Delay”). Each bank defines its Bank Mode, which dictates the number of tracks and voices per track.
- Voice Banks (3 tracks × 3 voices): Parameters shared across a trio, but affecting all 9 voices.
- Quad Banks (1 track × 4 voices): Used for the Quad Delay, Quad Reverb, and Partial Machine, allowing independent modulation for each speaker channel or frequency-dependent lane.
- Global Banks (1 track × 1 voice): Used for global settings like the Theory of Time clock or mastering EQ.

Crucially, the base value of a knob is identical for all voices within a track. However, modulation and gestures can apply different offsets to each voice within that track.

Base Encoders vs. Banked Encoders

StateEncoderCell: The base class that holds the actual numerical state. It stores a value in the normalized range [0, 1].
BankedEncoderCell: Extends the state cell to support deep, polyphonic modulation and macro gestures.

Deep Modulation

Every BankedEncoderCell can act as a modulation destination.

Up to 15 internal “LFOs” or envelopes (e.g., the PolyXFader LFOs, AHD envelopes) can be routed to any parameter.
The Modulation Depth is itself implemented as a full BankedEncoderCell. This means you can modulate the modulation depth (e.g., using an LFO to slowly fade in an envelope’s effect on the filter cutoff).
Polyphonic Modulation: While the base knob value is shared across a track, the modulation sources (like voice-specific envelopes) are polyphonic. Therefore, the resulting modulated parameter values are calculated independently for every voice.
Crossfade Modulation: To prevent clipping and dead spots, modulation is applied as a crossfade. A modulation depth of 1.0 means the parameter is 100% controlled by the modulator, completely overriding the base knob value.

Gestures (Macros)

Gestures are macro controls mapped to physical analog inputs (Like sliders and joysticks).

A gesture allows you to define a “Target State” for a parameter.
When the gesture is at 0.0, the parameter sits at its base knob value.
When the gesture is at 1.0, the parameter moves to the Target State.
Like modulation depths, the Target State is implemented as a full BankedEncoderCell (though hidden from the normal UI) and is polyphonic.
If you physically turn an encoder while a gesture is active, the system correctly updates the base knob or the Target State to match your physical action, ensuring the UI and physical knobs never fall out of sync.

Scene Morphing

The entire state of all encoders (base values, modulation depths, and gesture targets) is duplicated across two Scenes (SceneManager.hpp).

Scene 1 and Scene 2 act as complete snapshots of the synthesizer.
A global m_blendFactor crossfades between the two scenes.
Because every parameter is continuously interpolating between Scene 1 and Scene 2, moving the scene crossfader smoothly morphs every aspect of the sound engine simultaneously.

UI State and Parameter Slew

EncoderBankUIState: Manages the communication between the deep software state and the physical hardware/screen UI. It handles the rendering of LED rings and the processing of delta increments from physical endless encoders.
Parameter Slew: We only calculate the parameter values every eight samples on control frames, the DSP engine applies a slew filter (ParamSlew or FixedSlew) to the final, post-modulation parameter values before using them in audio calculations. During oversampled blocks, this slew rate is adjusted automatically.

Frequency-Dependent Quad Parameters

The Partial Machine uses a Quad bank differently from Delay and Reverb. Its four lanes are interpreted as anchors for FrequencyDependentParameter, not just four speaker channels. If all four lanes share the same base value, the parameter behaves like a normal scalar. If modulation produces different values per lane, each spectral partial interpolates a unique value from its frequency, allowing the same knob to create frequency-dependent attack, decay, density, bandwidth, panning, unison, pitch, and volume behavior.

See Partial Machine for the DSP-side mapping.

Machine-Specific Parameters

Each parameter in the Voice banks can specify which source and filter machines it applies to via bit vectors (MachineFlags). Parameters are defined in ForEachSmartGridOneParam.hpp with sourceMachines and filterMachines arguments (e.g. MachineFlags::x_dualWaveShapingVCOOnly for parameters that only affect the Dual Wave Shaping VCO source).

When the user selects a different source machine (e.g. Thru) or filter machine, UpdateEncodersForMachine() runs and swaps the actual encoder pointers in the grid. Parameters that do not apply are removed by placing nullptr in those positions, which leaves the cell empty and disconnected. This keeps the encoder grid relevant to the active machine while preserving encoder state in the owner array. The update is triggered on machine change (config page) and track change (since each track can have different machines).

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