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KSampler (Advanced)-node in ComfyUI

KSampler (Advanced) is KSampler with step-range control: add_noise, start_at_step, end_at_step and return_with_leftover_noise, used for base + refiner chains and two-model sampling.
Nodepakket: ComfyUI core
Categorie: Sampling
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Wat KSampler (Advanced) doet

The advanced sampler runs the same denoising loop but lets you sample only a slice of the schedule. With return_with_leftover_noise enabled and end_at_step set to, say, 20 of 25, the first sampler stops early and hands a still-noisy latent to a second KSampler (Advanced) that starts at step 20 with add_noise disabled. This is how the SDXL base/refiner workflow and many two-model tricks are built.
There is no denoise slider; denoise strength is expressed through the step range instead. start_at_step 10 of 20 steps is the same as denoise 0.5 on a plain KSampler.

Invoer

Naam
Type
Wat het is
model / positive / negative / latent_image
various
Same as KSampler.
add_noise
COMBO
enable to add fresh noise to the latent before sampling (first stage), disable to continue a partly sampled latent.
noise_seed
INT
The seed for the noise.
steps / cfg / sampler_name / scheduler
various
The full schedule; both stages should use the same total steps.
start_at_step
INT
First step to run. 0 for the first stage.
end_at_step
INT
Step at which to stop. 10000 means run to the end.
return_with_leftover_noise
COMBO
enable when another sampler will continue from this latent.

Uitvoer

Naam
Type
Wat het is
LATENT
LATENT
The (possibly partially sampled) latent.
AD
Sla de installatie over: ComfyUI-workflows voorgeïnstalleerd in de cloud
BitVector draait kant-en-klare ComfyUI-workflows op eigen GPU's. Geen installatie, geen ontbrekende nodes, geen rode vakken. Open het op je telefoon of laptop en genereer binnen een minuut.

Zo gebruik je KSampler (Advanced)

  1. Stage one: add_noise enable, start_at_step 0, end_at_step 20, return_with_leftover_noise enable, steps 25.
  2. Stage two with the second model: add_noise disable, start_at_step 20, end_at_step 10000, return_with_leftover_noise disable, same steps, scheduler and seed.
  3. Decode the second latent.

Instellingen en tips

  • Keep steps, scheduler and seed identical in both stages; only the model, prompts and step range change.
  • For img2img without a denoise slider: steps 20, start_at_step 10 equals denoise 0.5.
  • SDXL refiner was tuned for the last 20 percent of steps; with modern SDXL checkpoints it is usually unnecessary.

Problemen met KSampler (Advanced) oplossen

Second stage output is pure noise

Waarom het gebeurt
add_noise is enabled in the second stage, or return_with_leftover_noise was disabled in the first, so noise levels do not line up.

Zo los je het op
First stage: leftover noise enable. Second stage: add_noise disable, start_at_step equal to the first end_at_step.

Second stage looks over-smoothed or ignores the prompt

Waarom het gebeurt
The refiner stage runs too many steps or uses a different scheduler than the base stage.

Zo los je het op
Give the second stage the last 15-25 percent of steps and the same scheduler.

Nothing happens in the second sampler (output equals input)

Waarom het gebeurt
start_at_step is at or beyond steps, so there is nothing left to sample.

Zo los je het op
Make start_at_step smaller than steps and smaller than end_at_step.

AD
Start deze workflow vanaf je telefoon
Elke workflow op deze pagina staat voorgeïnstalleerd op BitVector, met modellen en custom nodes al op hun plek. Kies er een, typ een prompt, klaar. Nul installatie, niets te downloaden.

Vragen over KSampler (Advanced)

Can I use it as a normal sampler?

Yes: add_noise enable, start 0, end 10000, leftover disable is identical to KSampler at denoise 1.0.

How do I get denoise 0.35?

With 20 steps, start_at_step 13.

Verwante nodes

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Nodes repareren beu? Laat de cloud het doen
BitVector houdt honderden ComfyUI-workflows geïnstalleerd, bijgewerkt en getest op snelle cloud-GPU's. Geen Python, geen CUDA-fouten, geen VRAM-limieten. Werkt in elke browser.

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