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F_DELAY — Flexible Stereo Delay Effect Engine

Overview:
F_DELAY is a feature-rich, stereo delay module for Voltage Modular, offering smooth control over timing, feedback, filtering, and stereo imaging. With 10-second delay buffers, color filtering, and modulation inputs, it’s designed for everything from subtle echoes to complex rhythmic effects. Advanced internal signal processing ensures high-quality output, while custom controls provide precise tweakability.

Main Features:

  • Up to 10 seconds of delay time per channel (48,000 samples at 48kHz)
  • Individual controls for Delay Time, Feedback, Wet Mix, Groove, Color, and Output Level
  • Stereo signal path with pan positioning for the delay return
  • Built-in color filter per channel to shape delay tone (darker/warmer echoes)
  • Smooth parameter transitions using custom smoothing filters
  • Soft-clipping to prevent distortion artifacts
  • Modulation inputs for delay parameters (e.g., feedback, pan, color)
  • Toggle button to activate/deactivate delay effect in real time

Controls:

  • Delay Time: Sets the delay length (1 ms to 10,000 ms). Skewed for fine control at short times.
  • Delay Feedback: Controls how much of the delay output is fed back. Higher values result in longer trails.
  • Delay Color: Adds filtering coloration using a dedicated filter; negative values dampen highs.
  • Delay Wet: Mix between dry signal and delay return. 0 = fully dry, 1 = fully wet.
  • Delay Groove: Acts as a time multiplier/divider for delay modulation, adding rhythmic feel or swing.
  • Delay Out: Master output level of the delay return. Set between 0 and 2× gain.
  • Delay Pan: Stereo pan for the delay return; 0 = full left, 1 = full right.
  • Delay Toggle: Enables or disables the delay effect. Bypasses internal delay DSP when off.

Audio I/O:

  • Inputs: Stereo input jacks (L/R), plus additional modulation inputs (up to 5)
  • Outputs: Stereo delay return, automatically summed to mono if only one output is connected

Signal Processing Architecture:
F_DELAY uses two large ring buffers for the left and right channels, allowing delay times up to 10 seconds. Audio is processed through a custom smoothing engine (R_SmoothKnobVal) to prevent clicks and artifacts when changing parameters. Each channel is filtered using R_ColorFilter, which emulates analog-style high-frequency damping. Delay feedback is controlled with soft-clipping (softClip()) to maintain audio integrity even under high gain conditions.

Tips & Tricks:

  • Use Delay Groove to apply swing or rhythmic offset to delay repeats.
  • Turn up Delay Color for vintage/analog-style degradation on echoes.
  • Modulate Delay Pan to create moving, stereo echo effects.
  • Increase Delay Feedback and use short delay times to create comb filtering or flanger-like effects.
  • To simulate slapback delay, set Delay Time to under 100ms and Wet to 0.3–0.5.
  • Disable Delay Toggle for dry-through signal, useful when automating effect activation.

Internal Modules & Helpers:

  • R_SimpleRingBuffer — Manages delay buffers with support for linear interpolation
  • R_ColorFilter — Implements dynamic coloration/filtering for echoes
  • R_SmoothKnobVal — Ensures smooth transitions between knob values
  • softClip() — Limits feedback values to prevent distortion

Use Cases:

  • Classic delay effects: echoes, slapback, doubling
  • Experimental feedback loops with colored filtering
  • Time-based modulation effects via external CV (e.g., LFO to feedback)
  • Stereo delay imaging and rhythmic echo sculpting