Sunn was founded in 1965 in Tualatin, Oregon by brothers Conrad and Norm Sundholm. The company grew out of Norm's practical need for more powerful amplification — as bassist for the Portland-based band The Kingsmen, he found his gear inadequate for the large concert venues the band encountered during their national touring following the group's 1963 recording of "Louie, Louie." The brothers designed high-powered amplifiers, and demand quickly outpaced the capacity of their family garage, leading to the formal establishment of the Sunn Musical Equipment Company.

Sunn became known for tube amplifiers built for concert-level volume with unusually high headroom, capable of delivering clean tones at extreme output levels. Their amplifiers attracted artists including Pete Townshend of The Who, Jimi Hendrix — who signed an endorsement deal in 1968 — and Kurt Cobain, who used a Sunn Beta Lead during Nirvana's Bleach-era touring. The Model T, a high-powered all-tube amp head, became especially iconic in heavy music circles and is widely cited as a cornerstone of doom and sludge metal tones. Fender acquired Sunn in 1985 and eventually discontinued the brand in 2002.

A new group of music and electronics industry executives, working in partnership with Fender and Mission Engineering, licensed the brand and reformed Sunn Musical Equipment Corporation. The revived lineup includes the 100S (a 65-watt all-tube guitar amplifier), the 200S (a 60-watt all-tube bass amplifier), the solid-state Beta Lead and Beta Bass, and several speaker cabinet configurations including the DoomBox. The experimental drone-metal band Sunn O))) derived their name directly from the Sunn logo, reflecting the brand's deep cultural resonance within heavy music.

Sunn has 58 products cataloged on Equipboard, including Guitar Amplifier Heads, Bass Amplifier Heads, and Combo Guitar Amplifiers. Their gear is featured by 115 artists, with the strongest followings in Rock, Metal, and Electronic. Notable users include Stephen O'Malley, Greg Anderson, and Kurt Cobain. Sunn's catalog spans the full price spectrum — from entry-level options to high-end flagships.