Isobar Industries - Umbra

Umbra is a dual-channel feedback processor designed to bring controlled feedback into your patches. It lets you route external effects and modules through its send/return paths, feeding their output back into the signal to create anything from subtle resonances and repeating textures to heavy distortion and self-oscillating chaos. Filters, delays, reverbs, compressors and waveshapers can all become part of the feedback circuit, with dedicated controls for input level, return level and feedback amount.

The module uses three pairs of discrete transistor-core VCAs to control these different stages, with CV inputs for each. The input VCA sits before the feedback circuit, meaning you can reduce or completely close the incoming signal while the existing feedback continues to decay naturally (handy when when working with delays and reverbs for instance). An asymmetric diode soft-clipping stage at the output helps keep levels under control while also adding its own distortion and character as things get louder.

Umbra can operate in stereo, with two parallel processing paths, or in serial mono mode, where the left channel feeds into the right for two consecutive stages of processing and feedback. Input and return level have their own LEDs to monitor the signal, while the channel LEDs change colour to indicate the selected mode. It's a flexible tool for exploring feedback as a sound-design technique, but also great for adding saturation, movement and controlled instability to otherwise familiar effects.

Features:

• Dual-channel feedback processor with stereo and serial mono operation
• Three pairs of discrete transistor-core VCAs for input, return and feedback levels
• Individual send/return paths for inserting external modules and effects
• IMBUE: Input level control
• FEED: Feedback amount control
• DRAIN: Return level control
• CV control over all three VCA stages
• Switchable stereo/parallel and serial mono processing
• Serial mode routes the left channel into the right for two consecutive processing stages
• Input VCA positioned before the feedback circuit for natural feedback decay
• Asymmetric diode soft-clipping stage at the output
• Input and return level LEDs
• Colour-coded channel LEDs indicate the selected operating mode
• Normalled signal routing supports mono-to-stereo processing