Stax SRM-400S Earspeaker Driver Unit


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Mid class driver unit

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.


  • Type: All-stage FET configuration DC amplification driver unit
  • Frequency response: DC – 90kHz (with one SR-L500 MK2)
  • Gain: 60dB
  • Harmonic distortion: 0.01% or less (1kHz/100Vrms output)
  • Input impedance: 50kΩ (RCA), 50kΩx 2 (XLR)
  • Maximum output voltage: 400Vrms (1kHz)
  • Bias voltage: DC 580V
  • Operating temperature / humidity: 0 to 35 degrees C / less than 90% (non condensing)
  • Input terminal: RCA x 1, XLR x 1(mutual exclusion input)
  • Output: RCA parallel output terminal
  • Power consumption: 30W
  • Dimension: 195 (W) x 102 (H) x 376 (D) mm (maximum protruding portion included)
  • Weight: 3.4kg

Due to the bespoke nature of our high-end music systems this product is not available to be purchased online. Please contact us for personalized service from one of our team of experts.