Circle Audio is a microphone company founded by Keith Ross, a Grammy-nominated producer and mixer, alongside chief designer Langston Masingale, who also founded the transformer manufacturer LMI and Handsome Audio. The company's stated aim is to build studio-grade condenser microphones at prices well below the vintage and boutique tiers they emulate.

The brand's flagship product is the EVO 251, a tube condenser microphone designed as a modern take on the classic 251 topology. The mic is built around a proprietary LMI 143-S large-core transformer with nickel-and-steel laminations and a custom winding pattern, which the company highlights as the centerpiece of its sonic character. The lineup also includes matched power supplies and accessories, with limited-run colorways such as a Vintage edition of the EVO 251.

Circle Audio's product catalog is narrow by design, focused on the large-diaphragm tube condenser market rather than a broad range of studio gear. The EVO 251 has been discussed by engineers on forums such as Gearspace and sold through outlets like Reverb, positioning the brand within the enthusiast and professional recording community.

Circle Audio has 1 product cataloged on Equipboard, including Condenser Microphones.