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This A$687 asking price is a strong deal, sitting well below the 25th percentile of A$576 for recent comparable AUD listings and representing roughly one-third of the original A$2,100 retail cost. At this level, it is a genuine bargain for the Stax SRM-400S, a solid-state electrostatic driver unit that delivers the high-end performance of the SRM-700S lineage at a much more accessible price point.
The SRM-400S is well-regarded for its exceptional 0.01% harmonic distortion and wide DC to 90kHz frequency response, making it an ideal, versatile energizer for both pro-bias and standard Stax electrostatic headphones. Its compact solid-state design offers reliable operation with 60dB gain and 400V output, providing a significant performance upgrade over entry-level drivers without the maintenance needs of tube units. Unless the listing notes AC100V Japanese mains voltage requiring a transformer, this is a clean buying opportunity for a high-performing, rare-to-find used unit at an excellent price.
Independent perspective — not a price guarantee. Always verify condition, accessories and provenance before purchase.
Stax traces its origins to 1938 in Tokyo, Japan, when Naotake Hayashi founded Showa Kouon Co., Ltd. in Chiyoda-ku. Initially focused on wax disc recording, metal master production, and audio equipment for film soundtracks, the company evolved through the postwar era. In 1950, it launched its first high-frequency condenser microphone, adopted by NHK, and renamed itself STAX Co., Ltd. in 1963, honoring its pioneering Stax-1 mic. A brief suspension in 1995 due to economic pressures gave way to revival, preserving its legacy under family leadership.
The brand specializes in electrostatic headphones, known as "EARSPEAKERS," debuting with the world-first SR-1 in 1960. This innovation spawned enduring lines like the SR series, produced for decades with incremental refinements for superior resolution and staging. Stax complements these with dedicated electrostatic amplifiers and select accessories, eschewing conventional speakers, turntables, DACs, or cables to hone its transducer expertise.
Stax commands a niche high-end position among audiophiles and professionals, revered for unmatched transparency and fidelity that rivals cost-no-object loudspeakers. Its 85-year heritage cements it as a boutique icon in electrostatic technology, far from mass-market fare, appealing to discerning buyers seeking pinnacle sonic transduction.
See all Stax listings on RADAR.
