Stax SRM-400S Vacuum tube output driver

STAX SRM-400S driver amplifier for electrostatic headphones

With the SRM-400S transistor driver amplifier, STAX offers a further development of the proven SRM-353X mid-range model as an ideal power supply for the electrostatic headphones from the traditional Japanese manufacturer such as those of the Lambda series (STAX SR-L300, STAX SR-L500 MK2, STAX SR-L700 MK2) or to upgrade the entry-level model SRS-3100.

What's new?

The SRM-400S has a newly developed DC amplifier stage, which is based on the complex circuit design of the SRM-700S top amplifier. With specially manufactured and extremely low-noise DUAL-FET transistors, the outstanding sound quality of the amplifier is once again raised to a new level. For improved efficiency while reducing power consumption, the SRM-400S also features a new transformer with separate windings for the high and low voltage circuits. The better stiffened and low-resonance steel housing with an increased proportion of non-magnetic aluminum effectively reduces both vibration and eddy currents and offers the SRM-400S an even more undisturbed working environment.

By improving the components and changing the circuit layout, the new transistor driver amplifier sets completely new standards in terms of sound in this price range.

variety of connections

STAX electrostatic headphone driver amplifiers can be driven from the recording output (Tape/Record Out or Fixed Out) or from another fixed-level output (Pre Out/Fixed Out) of a preamplifier or integrated amplifier. Of course, a CD player or a turntable with a separate phono preamplifier can also be used directly as the signal source. The music signal present at the input of the driver amplifier can be looped through - this means that another device can be supplied with music signals. A separate D/A converter is required for the digital connection of a source device.

execution

• Brushed aluminum front in silver / dark gray body.

Technical specifications

• Transistor output stage without negative feedback
• Signal-symmetrical circuit design
• Volume/balance control via four-way potentiometer
• One switchable input: either balanced (XLR) or unbalanced (RCA/Cinch)
• One unbalanced output (RCA/Cinch)
• Two headphone outputs (simultaneous operation of two STAX headphones possible)
• Dimensions W x H x D: 195 x 102 x 346 (with knob and sockets 376) mm
• Weight: 3.4kg

Note on the operating voltage (polarization voltage) of STAX headphones

Many early STAX headphones are designed for an operating voltage of 230V/DC. Headphones from the PRO series - including all current models - require a higher operating voltage of 580V/DC.

In the past, driver amplifiers were offered which also provided both operating voltages. Current devices only have connections for the higher operating voltage of 580V/DC.

To avoid confusion, the connection sockets for the different operating voltages have different contacts.