Circuit Abbey is a small American Eurorack module manufacturer founded in 2010. The brand operates under a whimsical "Trappist monks" persona, but is run by engineers with a passion for electronic music and a fondness for bourbon. Circuit Abbey first gained attention in the modular synth community with the Gravity Well, a wave modifier that uses asymmetrical wave warping to shape audio signals.

The company is known for its space-efficient designs, with many modules fitting into compact 2HP and 4HP formats — an appealing trait for modular synthesists looking to maximize their rack real estate. Key modules include the Gozinta (a dual-channel input amplifier with up to 24 dB of gain and clipping-driven distortion), the ADSRjr (a feature-rich 4HP envelope generator with CV control), the Invy (a dual attenuverter and offset utility), the G8 (an 8-mode clock divider), and the Unify (a 12HP four-channel stereo mixer with headphone output). Circuit Abbey also produces the Euro-Duino line of Arduino-based programmable modules and the Tube Ringmod, a vacuum tube-based ring modulator.

Many Circuit Abbey designs are available as both assembled units and DIY kits through retailers like synthCube, reflecting the brand's roots in the hands-on, builder-oriented ethos of the Eurorack community. The company's catalog spans utility modules, mixers, envelope generators, filters, clock tools, and effects processors — a broad range that has earned it a dedicated following among modular enthusiasts.

Circuit Abbey has 5 products cataloged on Equipboard, including Modular Synthesizers. Their gear is featured by 3 artists, with the strongest followings in Electronic, Rock, and Pop. Notable users include Andrew Huang, Richard Devine, and Celldweller.