A solid-state energiser for STAX PRO-class electrostatic earspeakers. The Stax SRM-400S has a newly designed power transformer for the low voltage circuit winding, improving power efficiency and sound quality. The audio signal is amplified with a distortion of less than 0.01%
A new chassis is also featured, which is more rigid than previous models. Constructed of aluminium, it reduces environmental factors such as vibration. Inputs are RCA and XLR.