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STAX SRM-500T Vacuum Tube Driver Unit For Earspeakers


STAX SRM-500T Vacuum Tube driver unit:

Legendary electrostatic headphones for audio fanatics


Complete model change for the first time in 11 years

The SRM-500T, which follows the numerical sequence of the SRM-700 series, is the successor model to the vacuum tube driver unit SRM-006tS and is 11 years in the making.

STAX custom-made low-noise DUAL FET is used for the first stage, and high-voltage double triode 6FQ7 / 6CG7 is used for the output stage. While following the traditional circuit design which is perfect for  STAX vacuum tube drivers, we have improved the efficiency of the power supply and  further improved the sound quality.

In addition to the conventional power transformer for the high voltage circuit, the newly designed power transformer with the winding for the low voltage circuit is installed in SRM-500T. By adopting this low-voltage winding, the efficiency of the power supply has improved, and compared to conventional vacuum tube driver units such as the SRM-006tS, power saving and improved sound quality have been achieved.


In addition, a new chassis with increased rigidity compared to SRM-006tS has been adopted. The hybrid structure, which uses a lot of non-magnetic aluminium, further suppresses the effects of physical external noise such as vibrations. The inputs are RCA and XLR, the mutual exclusion inputs. The custom made concentric dual volume knob which is common to STAX products and RCA PARALLEL OUT functions are installed same as the conventional driver units. All electric components are strictly selected considering the environment. Also the sound quality and the performance is improved. The complete DC ampli er con guration that the signal circuit includes no coupling condensers is one of the biggest traditional features.

The clear and highly transparent sound, a feature of the vacuum tube circuit and the warm and wide sound texture are maintained and the thickness of the low-mid range is brushed up.

Therefore we recommend the SRM-500T in combination with the advanced lambda series earspeakers (SR-L300/SR-L500 MK2/SR-L700 MK2).

    • Type: FET + vacuum tube output hybrid DC amplifier configuration / driver unit
    • Vacuum tube : 6FQ7 / 6CG7
    • Frequency response: DC to 90kHz (when using one SR-L500 MK2)
    • Gain: 60dB
    • Harmonic distortion rate: 0.01% or less (at 1kHz / 100V r.m.s. output)
    • Input impedance: 50kΩ (RCA), 50kΩ x 2 (XLR)
    • Maximum output voltage: 300V RMS (1kHz)
    • Bias voltage: DC 580V
    • Operating ambient temperature / humidity: 0 to 35 ° C / 90% or less (however, no condensation)
    • Input: RCA x 1 XLR x 1
    • Output: RCA out
    • Power consumption: 38W
    • Dimensions: 195W x 102H x 376Dmm (including protrusions such as knobs)
    • Weight: 3.4kg
    • Country of origin: Japan

Brandstraat 28
9255 Buggenhout