Exciter (Entropy Tap) — `GDVP_NODE_EXCITER` ✅

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A noise / randomness source — but a clever one. The Exciter generates nothing of its own; it taps a single shared noise engine, selects a color, a per-voice read offset (for decorrelation across a chord), and a shaping mode, then forwards that palette. This gives you everything from colored audio noise to Geiger-counter dust to Buchla-style stepped voltages. Source: gdvp_dsp_exciter.c, payload gdvp_node_exciter_t in gdvp_nodes.h.

Signal & ports

Output (port 0): the generated/shaped entropy signal — route it as an audio source (noise layers, percussion excitation) or as a modulation source (random CV).

Parameters

Parameter	Param ID	Range	Meaning
Source mode	`GDVP_PARAM_EXCITER_SOURCE_MODE`	0–4	`0`=Audio noise, `1`=Particle (Poisson dust), `2`=S&H step, `3`=S&H quantized, `4`=S&H smooth
Color	`GDVP_PARAM_EXCITER_COLOR`	0–4	`0`=White, `1`=Pink, `2`=Red, `3`=Blue, `4`=Violet
Rate / density	`GDVP_PARAM_EXCITER_RATE`	0–16383	S&H clock rate, or particle density
Level	`GDVP_PARAM_EXCITER_LEVEL`	0–16383	Output level
Param A	`GDVP_PARAM_EXCITER_PARAM_A`	0–16383	Context-dependent: slew amount \| quantize steps \| dust amplitude
Decorrelation offset	`GDVP_PARAM_EXCITER_DECORR_OFFSET`	0–16383	Per-voice read-phase spacing into the shared ring (see decorrelation)
Flags	`GDVP_PARAM_EXCITER_FLAGS`	bitmask	bit0 Bipolar, bit1 Tempo-sync, bit2 Gaussian, bit3 Crush
Crush bits	`GDVP_PARAM_EXCITER_CRUSH_BITS`	0–…	Bit-depth reduction mask power (`0` = off)

Behaviour notes

Source families

Audio (0): continuous colored noise — beds, wind, breath, filter excitation.
Particle (1): density-gated Poisson impulses — dust, crackle, Geiger/rain textures. Param A sets impulse amplitude; Rate sets density.
S&H step (2): classic sample-and-hold staircase random voltage.
S&H quantized (3): stepped random snapped to a grid (Buchla 266 flavour); Param A = steps.
S&H smooth (4): slew-limited fluctuating random — a "drunk walk" / Wogglebug; Param A = slew.

Color

The five colors are spectral tilts of the shared white source: White (flat), Pink (−3 dB/oct), Red/Brown (−6 dB/oct), Blue (+3), Violet (+6). Pink/red are smoother and darker; blue/violet are brighter and hissier.

Per-voice decorrelation

Because all exciters tap one shared noise ring, a chord could otherwise sound mono-coherent (every voice identical). The decorrelation offset shifts each voice's read point by voice_idx × offset (clamped to the history window), so each voice reads independent past samples. Offset 0 across a chord = one unified mono bed; spread offsets = a diffuse, statistically independent field. The voice index is published to the kernel by the executor just before dispatch (gdvp_noise_set_voice_context), the same pattern the filter cascade uses.

Tempo-sync & crush

With the tempo-sync flag, the S&H clock latches on transport ticks from the executor's tick_mask (sample-accurate). The crush flag plus crush_bits applies bit-depth reduction for lo-fi/digital grit. Gaussian sums two draws for softer noise statistics; bipolar swings the output around zero rather than unipolar.

Percussion: pair with a fast Envelope and Filter — see noise_snare, metallic_hat, vinyl_dust examples (library).