STAX SRM-500T Vacuum Tube Electrostatic Driver




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Stax introduces this new model, the SRM-500T, to replace the previous SRM-006tS driver unit. SRM-500T features a pair of 6FQ7/6CG7 vacuum tubes as the output stage, driven by custom-made low noise dual FET. STAX prides itself in offering a great value electrostatic driver at the best possible performance.

In addition to the conventional power transformer for the high voltage circuit, the SRM-500T features newly-designed power transformer with windings for the low voltage circuit. This low voltage winding improves power efficiency and achieves better sound quality than conventional vacuum tube output driver units.

An improved, more rigid chassis is installed, using a hybrid structure of non-magnetic aluminium which further reduces the effect of vibrations and environmental noise factors.

The inputs are RCA and XLR, both mutual exclusion design. The custom-made concentric dual volume knob which is common to STAX products and RCA PARALLEL OUT functions are installed as per conventional driver units. All electric components are strictly selected considering the environment, sound quality and overall performance is improved.

The complete DC amplifier configuration includes no-coupling condensers, one of the biggest traditional features. Delivering clear and highly transparent sound - a feature of this vacuum tube circuit - in addition to a warm, wide texture, and improved thickness of the low-mid range. This driver unit is the new choice for the advanced lambda series earspeakers (SR-L300/SR-L500 MK2/SR-L700 MK2).


  • Full update to the mid-level STAX vacuum tube output driver unit.
  • Successor to the SRM-006tS.
  • STAX custom-made low noise DUAL FET.
  • Newly-designed power transformer.
  • Hybrid structure non-magnetic chassis.
  • Ideal match with STAX SR-L300 / SR-L500 MK2 / SR-L700 MK2 Earspeakers.


  • Type: FET input + vacuum tube output hybrid DC amplification driver unit
  • Vacuum Tube: 6FQ7/6CG7
  • Frequency Response: DC - 90 kHz (with one SR-L500 MK2)
  • Gain: 60 dB
  • Harmonic Distortion: 0.01% or less (1 kHz / 100 V RMS output)
  • Input Impedance: 50 kΩ (RCA), 50 kΩ x2 (XLR)
  • Maximum Output Voltage: 300 V RMS (1 kHz)
  • Bias Voltage: DC 580 V
  • Operating Temperature / Humidity: 0 - 35 °C / less than 90% (non condensing)
  • Input Terminal: RCA x 1, XLR x 1 (mutual exclusion input)
  • Output: RCA parallel output
  • Power Consumption: 38 W
  • Dimension: 195 (W) x 102 (H) x 376 (D) mm (maximum protruding portion included)
  • Weight: 3.4 kg

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