378 Amplifiers is a boutique tube amplifier builder that specializes in meticulous clones of the vintage Sunn Model T, a 1970s all-tube head favored in heavy and experimental music. The company is also known under its Roman-numeral styling IIIVIIVIII. Their lineup centers on 75W and 150W Model T-style heads that track the first and second generation circuits, alongside matching 2x12 and 4x12 guitar and bass cabinets, pedals, and replacement parts.

The amps are hand-built in small batches and marketed toward players chasing the thick, saturated low-end and harmonically rich overdrive associated with the original Sunn designs. The brand has developed a following in doom, drone, stoner, sludge, and noise-rock circles, where the Model T platform is a reference tone.

378 Amplifiers has 1 product cataloged on Equipboard, including Guitar Amplifier Heads.