Coil Audio is a boutique audio equipment manufacturer based in Lawrence, Kansas, specializing in hand-built microphone preamps, audio transformers, and related power supplies and chassis. The company's visual aesthetics and circuit topologies draw directly from vintage 1930s and 1940s American tube recording equipment designed by firms such as RCA, Altec, Western Electric, Langevin, and Gates.

The product lineup centers on the CA-70 and CA-286 preamps, offered as both PS6 modular units and CA-70S/CA-286S single-channel standalone versions, alongside the CP-448 phantom power unit. The CA-70 is based on a two-stage circuit originally invented by Western Electric in 1913 and licensed by various manufacturers through the 1950s. A defining feature of Coil's preamps is the use of exterior octal sockets for input and output transformers, allowing users to swap between several transformer options to color the sound.

The preamps are hand-assembled and tested in the USA using custom interchangeable transformers along with NOS (new old stock) capacitors, resistors, and octal tubes. Coil's approach emphasizes user control over circuit parameters, giving engineers a wide range of tonal shaping for tracking and mixing applications.

Coil Audio has 3 products cataloged on Equipboard, including Preamps. Their gear is featured by 6 artists, with the strongest followings in Rock, Pop, and Folk, World, & Country. Notable users include Ryan Petersen, Glenn Rosenstein, and Vance Powell.