AER is a German manufacturer of acoustic instrument amplifiers based in Velbert, in the Ruhr area. Founded in 1992 by Udo Rösner, Michael Eisenmann, and Susanne Janz, the company set out to build reference-class amplifiers that reproduce the natural voice of acoustic instruments rather than coloring them. All products are designed and assembled at AER's Velbert facility, and the company markets itself under the tagline 'The Acoustic People.'

AER's catalog is organized around four product lines: the Acoustic Line for acoustic guitar and general instrument amplification, a Bass Line for upright and acoustic bass, a PA Line for small-format live sound, and an Accessories Line. The brand is best known for the Compact 60, a small 60-watt combo that became a standard on acoustic stages and has gone through multiple generations, along with related models such as the Compact 30, Alpha, Domino, and the larger AcoustiCube. AER also offers signature variants including the Compact 60 Tommy Emmanuel Signature and the MM200 Monte Montgomery Signature.

The brand has a strong following among fingerstyle, jazz, and classical guitarists, as well as singer-songwriters who value a transparent, feedback-resistant sound at moderate stage volumes. Artists associated with the brand include Tommy Emmanuel, Monte Montgomery, Martin Taylor, Stochelo Rosenberg, David Tanenbaum, Lionel Loueke, and violinist Didier Lockwood.

AER has 14 products cataloged on Equipboard, including Acoustic Guitar Amplifiers, Combo Guitar Amplifiers, and Preamps. Their gear is featured by 13 artists, with the strongest followings in Rock, Jazz, and Folk, World, & Country. Notable users include Tommy Emmanuel, Becca Stevens, and Miguel Talavera.