Feedback paths aren’t the first thing people think of when it comes to sound design. The concept of feedback patching itself can be a little confusing, setting up a loop requires a decent amount of modules, and your audio can get out of control quickly.
If you don’t have a spare attenuators, mults, and mixers lying around and still want to add feedback patching to your arsenal of sonic tools, then Isobar Industries has just released a solution. Meet Umbra, a stereo feedback accumulator that makes this type of technical patching more accessible and looks gorgeous while doing it.
We got some face time with this module at Knobcon 2025 and now its in the hands of some very talented musicians. One of which – Metamyther – just dropped a feedback exploration video of Umbra across multiple use cases: from Vhikk X powered drones to straight signal saturation. Check it out above!
What Is Umbra?
Umbra is a dual-channel stereo feedback processor from Isobar Industries designed to create controlled feedback loops with any Eurorack modules.
Umbra provides precise control over feedback processes in a compact, 10hp module. Panel LEDs give you real-time signal level monitoring, making it easy to find sweet spots and avoid unwanted peaks. Beyond feedback loops, it works as a high-quality saturator, stereo processor, or dynamics controller thanks to its discrete transistor stages and soft clipping circuitry.
Umbra Features
- Stereo or serial mono send/return jacks let you insert effects, filters, or processors into the feedback path
- Discrete transistor VCA circuits for input gain, feedback amount, and return gain
- Built-in soft clipping prevents runaway feedback and adds harmonic saturation
- Input level control positioned before the feedback circuit for natural fade behavior
- Stereo normalling allows mono-to-stereo or true stereo operation
Umbra is available from the Isobar Industries Etsy site for $289. This is a built-to-order module so expect an assembly time of ~3 weeks before it ships.
More Feedback Patching
There are some great resources online for both learning the technical approach to feedback patching and hearing how feedback patches can sound.
First, Knobulism has an excellent feedback fundamentals guide. There are patch diagrams for dynamically controlling amplitude, multiple types of delay patches, and even advanced techniques like oscillator self-patching.
Interestingly, Patch & Tweak doesn’t have any dedicated feedback sections. Even in the P&T glossary, under ‘F’, we only get Filter, FM, Formant, and Function Generator defined terms. In The Computer Music Tutorial (2nd Edition) by Curtis Roads there is plenty of feedback related content, but it’s more in the technical implementation of different types of synthesis or time-based effects.
Feedback Patching Videos
If you look, YouTube will reward you with some amazing feedback patching content. We’ve put together a small playlist with a nice variety of hardware (and software) feedback demos: modular, Ableton, and VCV Rack.
One playlist that stands out is 6 years old from DivKid, where he explores single-module self patching across what would now be considered “classic” modules.
Have fun watching.
If you’ve got an Umbra on the way, definitely drop links to any sonic madness you create.
If you haven’t patched up a feedback loop before, now’s the time to experiment!
