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F_PHASR8 – 4/6/8-Stage Optical Phaser

F_PHASR8 is an analog-style phaser with an optical (lamp/LDR) modulation model and up to eight cascaded all-pass stages. It delivers classic sweeping notches, vintage optical smoothness, stereo width, and feedback coloration.

Inputs / Outputs

  • IN L, IN R — Audio inputs. If only IN L is connected, the signal is duplicated to the right channel.
  • OUT L, OUT R — Stereo audio outputs.

Controls

  • RATE (0.01–5.00 Hz, default 0.50) — LFO speed that “drives the lamp”.
  • DEPTH (0.00–1.00, default 0.85) — Modulation depth applied to the sweep width.
  • CENTER (80–2000 Hz, default 500) — Mid frequency around which the notches sweep.
  • WIDTH (0.0–3.0 oct, default 2.0) — Sweep span in octaves.
  • FEEDBACK (−0.95…+0.95, default +0.50) — Feeds the wet signal back into the input for sharper, more resonant notches. Negative values change the phaser’s color.
  • MIX (0–1, default 0.50) — Dry/Wet blend.
  • STEREO PHASE (0–180°, default 90°) — Phase offset between L and R LFOs for stereo width.
  • OPT SLEW (5–800 ms, default 120 ms) — Optical response time. Higher values = slower, gooier “LDR-like” motion.
  • STAGES (4 / 6 / 8) — Number of all-pass stages. More stages → more notches and a deeper sweep.

Panel Indicators

  • LAMP LED — Shows the internal optical lamp brightness (0–1) after slew. It visualizes the optical driver that controls the sweep.

How It Works

  1. A sine LFO drives a virtual lamp (0–1).
  2. The lamp signal is passed through an exponential slew (OPT SLEW) to emulate LDR inertia.
  3. The slewed value maps logarithmically to filter cutoff around CENTER with span WIDTH and amount DEPTH.
  4. Audio passes a cascade of 4/6/8 first-order all-pass stages (per channel).
  5. FEEDBACK feeds the wet signal back, then MIX blends with the dry path.

Tips & Usage

  • For vintage glide, keep OPT SLEW between 80–200 ms; for modern snappy motion, reduce to 10–40 ms.
  • STEREO PHASE ≈ 90° gives a wide image; 0° yields mono-locked sweeps.
  • Try small negative FEEDBACK (−0.2…−0.4) for a different tonal color that sits well in dense mixes.
  • CENTER ≈ 300–800 Hz is a sweet spot for classic guitar/keys; widen WIDTH for more movement.
  • Use 4 stages for subtle shimmer, 6 for a clear but controlled sweep, 8 for deep, liquid motion.

Example Settings

  • Classic 4-Stage Swirl: Stages=4, Rate=0.40, Depth=0.70, Center=600, Width=1.2 oct, Feedback=+0.35, Mix=0.50, Stereo Phase=60°, Opt Slew=120 ms.
  • Mix-Friendly 6-Stage: Stages=6, Rate=0.25, Depth=0.60, Center=450, Width=0.9 oct, Feedback=+0.25, Mix=0.40, Stereo Phase=90°, Opt Slew=140 ms.
  • Deep 8-Stage Liquid: Stages=8, Rate=0.35, Depth=0.90, Center=500, Width=2.0 oct, Feedback=+0.55, Mix=0.55, Stereo Phase=120°, Opt Slew=160 ms.
  • Subtle Stereo Movement: Stages=6, Rate=0.15, Depth=0.35, Center=700, Width=0.6 oct, Feedback=+0.10, Mix=0.30, Stereo Phase=90°, Opt Slew=100 ms.
  • Snappy Wah-Like: Stages=4, Rate=2.00, Depth=1.00, Center=800, Width=1.5 oct, Feedback=+0.20, Mix=0.60, Stereo Phase=0°, Opt Slew=20 ms.
  • Wide Slow Ocean: Stages=8, Rate=0.08, Depth=0.80, Center=400, Width=2.5 oct, Feedback=+0.45, Mix=0.50, Stereo Phase=150°, Opt Slew=220 ms.
  • Negative-FB Color: Stages=6, Rate=0.50, Depth=0.75, Center=520, Width=1.8 oct, Feedback=−0.35, Mix=0.55, Stereo Phase=90°, Opt Slew=130 ms.
  • Drum Bus Tuck-In: Stages=4, Rate=0.20, Depth=0.30, Center=350, Width=0.5 oct, Feedback=+0.10, Mix=0.25, Stereo Phase=45°, Opt Slew=90 ms.
  • Ambient Pad Swim: Stages=8, Rate=0.12, Depth=0.85, Center=450, Width=2.2 oct, Feedback=+0.50, Mix=0.60, Stereo Phase=120°, Opt Slew=200 ms.
  • Bass-Safe Glide: Stages=6, Rate=0.18, Depth=0.45, Center=300, Width=0.8 oct, Feedback=+0.15, Mix=0.35, Stereo Phase=60°, Opt Slew=110 ms.

Troubleshooting

  • No movement? Increase DEPTH, reduce OPT SLEW, or raise RATE.
  • Too hollow or phasey? Reduce MIX or try fewer STAGES. Adjust CENTER upward.
  • Harsh peaks? Lower FEEDBACK or try a small negative value.
  • Mono collapse? Set STEREO PHASE closer to 90–120° for width; 0° is effectively mono.

Notes

  • Factory behavior duplicates mono input to stereo if IN R is unused.
  • LED shows the slewed lamp value (0–1) and is not an audio meter.
  • Very slow rates (<0.05 Hz) can sound nearly static; increase DEPTH or use wider WIDTH for audibility.