Umbra

Stereo Feedback Looping Environment

Umbra is a stereo feedback processor with dual discrete VCAs. Route any external effects through its send/return paths to create feedback loops ranging from subtle echoes to howling walls of sound. The VCAs are positioned before the feedback circuit, allowing time based sounds to fade naturally when the VCA is closed. A soft clipping stage after the feedback circuit keeps things controlled while adding grit. The left-right channel normalling allows for both mono-to-stereo or true stereo operation.

Features

• True stereo signal path
• Left channel normalled to right to create stereo signal
• Linked controls for stereo operation
• CV-controllable feedback and VCA levels
• Soft clipping circuit on output
• LED per channel for feedback monitoring
• Clip indication LEDs
• All-analog design

Controls

• Main Level slider (controls both channels)
• Level CV attenuverter knob
• Feedback Amount slider (controls both channels)
• Feedback CV attenuverter knob

Inputs/Outputs

• 2x Audio inputs (L/R, right normalized to left)
• 2x Send outputs (L/R)
• 2x Return inputs (L/R)
• 2x Processed outputs (L/R)
• 2x CV inputs (Level and Feedback)

Technical Specifications

• Width: 10HP

Patch Ideas

1. Two-Stage Serial Processing: Leave channel 2's input jack unplugged to create two stages of cascading feedback effects. The first channel's output feeds directly into the second channel's processing chain, creating complex, distorted and evolving textures with each stage having its own return effects.
2. Mono to Stereo Expansion: Use a mono source and let the normalling split it to both channels, making the signal stereo.
3. Stereo Reverb Loops: Process stereo reverb through the feedback path to build immersive spaces. Use CV modulation on the feedback for evolving textures.
4. Dual Mono Processing: Use each channel independently with different effects for parallel feedback experiments, unified by the shared controls.

Design Notes

The pre-feedback VCA placement ensures natural decay when reducing levels. The soft clipping circuit provides gentle saturation when pushed. Dual LEDs help you monitor feedback levels in both channels while patching. The shared controls make it easy to maintain consistent stereo imaging while still allowing for complex stereo effects when using different processors in each channel's feedback path.

Included

• Umbra module
• 4x M3 mounting screws
• Power cable