Stax SRM-700S Earspeaker Driver Unit


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The SRM-700S is an electrostatic headphone driver utilising a fully discrete dual FET. The output of the J-FET and the large current emitter follower circuit is low noise, bringing accurate music reproduction without missing any fine details.

STAX produce exclusively electrostatic headphones, or “earspeakers” since 1938. STAX chose the electrostatic technology for its ability to produce transparent sound, and low weight for comfort/ergonomics, both due to the driver design not employing fixed magnets and moving coils, as opposed to other common headphone driver designs. The minimal weight of the driver ensures a very quick response to the signal, creating a more faithful sound reproduction.


  • Type: All-stage FET configuration DC amplification driver unit
  • Frequency response: DC – 100kHz (with one SR-009S)
  • Gain: 60dB
  • Harmonic distortion: 0.01% or less (1kHz/100Vrms output)
  • Input impedance: 50kΩ (RCA), 50kΩx 2 (XLR)
  • Maximum output voltage: 450Vrms (1kHz)
  • Bias voltage: PRO 580V
  • Operating temperature / humidity: 0 to 35 degrees C / less than 90% (non condensing)
  • Input terminal: RCA x 1, XLR x 1
  • Output: RCA parallel output terminal
  • Power consumption: 46W
  • Dimension: 240W x 103 H x 393 D mm (maximum protruding portion included)
  • Weight: 6.3kg
Stax SRM-700S Electrostatic Headphone Amplifier

This amplifier is certainly much more than just another “solid performer” like the ones that hit the market on a regular basis. The SRM-700S with electrostatic headphones leave electrodynamic headphones firmly in the dust and challenges even the best of speakers and setups with their accuracy and lifelike performance. more...