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STAX SRM-727II Electrostatic Headphone Amplifier

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The electrostatic method is a playback method which involves the installation of drive electrodes on either side of a high-polymer film diaphragm with a thickness of only a few microns into each of which a plus signal and a minus signal are fed. This means that XLR connection with a pure balance output CD player makes it possible to listen to the original sound permitted by the balance system without a conversion circuit.

The output stage has been incorporated by newly developing a non-feedback (NON-NFB) large current emitter follower Class A amplification circuit. This makes it possible to achieve a much more vivid and dynamic sound quality.

The emitter follower at the output stage makes it possible to achieve lower impedance. A major expansion in dynamic range in the upper frequency has also been achieved.

DC amplifier configuration without the use of a coupling condenser.

A high sound quality, low noise FET is used at the input stage with a simple two-stage amplifying circuit. A natural and pure sound quality with high information quantity is realized.

When connecting your favorite attenuator or pre-amplifier, a direct switch that avoids duplication of the volume unit is included.

Careful selection of parts with high consideration on sound quality, performance, and the environment.

In order to avoid magnetic distortion, the chassis is made of aluminum materials, thereby contributing to purity of sound.

Amplification is set at a low level, thereby facilitating subtle adjustment of volume during XLR input and when using high-output CD players, etc.

Parallel output terminals (RCA) are included to enable the signal to pass through.

A new panel face has been designed with rounded corners and a silver brushed finish.

Earspeakers of PRO bias (5-pin) type can be used.

Control functions are restricted to the volume, and the input uses a single selecting system between RCA or XLR. This is a drive unit for exclusive use with earspeakers with emphasis placed first and foremost upon purity.


● Frequency response: DC-115 kHz (SR-007 or SR-404, when using one unit)
● Rated input level: 200 mV / 100 V Outputs
● Maximum input level: 30 V r.m.s. / at Minimum volume
● Amplification: 54 dB (x 500)
● Total harmonic distortion:0.01% / 1 KHz, 100 V r.m.s. output SR-007 or SR-404 Signature, when using 1 unit
● Input impedance: 50 KΩ / XLR balance 50KΩ×2
● Input terminals: RCA×1 or XLR×1 (balanced)
● Maximum output voltage: 450 V r.m.s. / 1 KHz
● Standard bias voltage: DC 580 V
● Power voltage: 120-240V ±10%, 50 to 60 Hz (adjusted for your area)
● Power consumption: 46 W
● Temperature range for use: Between 0º and 35ºC, max. 90% (no condensation)
● External dimensions: 195 (w) x 103 (h) x 420 (d) mm (including VR knob and pin jack (20 + 10)
● Weight: 5.2 Kg

About STAX

STAX produce exclusively electrostatic headphones, or “earspeakers” as they call them, in Japan, 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.