STAX SRM-700S Electrostatic Headphone Amplifier, Wired, Silver

STAX SRM-700S Electrostatic Headphone Amplifier (Silver)

Hear everything, add nothing

Experience the hush between notes, the snap of transients, and the truth of your recordings through an ultra-low-noise, all‑FET electrostatic driver. SRM‑700S is voiced for absolute clarity and dynamic ease, letting STAX earspeakers disappear and your music take center stage. Built to disappear sonically and integrate seamlessly into reference systems, it’s the solid‑state energizer discerning electrostatic listeners have been waiting for.

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Why Audiophiles Choose This Product

• Balanced, grain‑free speed and control
  The SRM‑700S delivers a black background with vanishing low distortion, preserving microdetail and macro‑dynamics across the full bandwidth of your STAX earspeakers. What Hi‑Fi? praised the SR‑009S/SRM‑700S combination for its “completely silent” background and super‑clean, distortion‑free presentation.

• Advanced all‑FET architecture with J‑FET output stage
  A newly developed, fully discrete topology uses a custom low‑noise dual FET at the input and, for the first time in a STAX driver, a J‑FET second stage feeding a large‑current emitter follower—engineered to keep high‑frequency content linear and effortless.

• Quiet confidence, purposeful ergonomics
  Dual 5‑pin PRO bias outputs on the front panel allow quick A/B comparisons or shared listening. A dual‑axis volume control provides precise channel balance, and a bypass mode lets you hand level control to an external preamp without repatching.

• System‑friendly connectivity
  Switchable balanced XLR and single‑ended RCA inputs plus RCA parallel out make it easy to insert the SRM‑700S into dedicated headphone rigs or full‑size stereo systems. A rear‑panel GND post helps tame hum in complex setups.

• STAX build and heritage
  Precision‑selected FETs, EMI‑shielded volume control, WIMA film capacitors, and high‑grip aluminum insulators reflect STAX’s meticulous approach—backed by a legacy of electrostatic innovation “since 1938.”

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What’s Included

• STAX SRM‑700S Electrostatic Headphone Amplifier (Silver) — all‑FET DC‑coupled driver with J‑FET second stage
• AC power cable
• RCA interconnect cable
• Warranty card
• Owner’s manual
  Accessories confirmed from the SRM‑700S owner’s manual.

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Technical Specifications

Specification	Value	Notes
Product Type	Wired	Analog electrostatic headphone driver (energizer) with STAX PRO 5‑pin outputs.
Circuit Topology	All‑stage FET, DC‑coupled; J‑FET second stage	Custom low‑noise dual FET input; J‑FET + large‑current follower output.
Frequency Response	DC – 100 kHz (with one SR‑009S)	Preserves extreme bandwidth and transient fidelity.
Gain	60 dB	Suited to line‑level sources.
THD	≤0.01% (1 kHz/100 Vrms)	Low distortion for high transparency.
Max Output Voltage	450 Vrms (1 kHz)	High headroom for modern PRO‑bias earspeakers.
Bias Voltage	PRO 580 V	For STAX PRO‑bias (5‑pin) earspeakers; not compatible with legacy “Normal” bias.
Inputs	1 × XLR (balanced), 1 × RCA (single‑ended)	Rear‑panel selector for XLR/RCA.
Line Output	RCA parallel out (through)	For daisy‑chaining another driver or feeding a stereo amp.
Volume Bypass	Internal/External level control switch	Integrates with a preamp; LED status on front panel.
Headphone Outputs	2 × STAX PRO 5‑pin	Dual front‑panel outputs for easy comparisons.
Input Impedance	50 kΩ (RCA), 50 kΩ ×2 (XLR)	Source‑friendly loading.
Power Consumption	46 W	Linear supply with robust heat management.
Dimensions (W × H × D)	240 × 103 × 393 mm	Allow ventilation above and to the sides.
Weight	6,300 g	High‑mass chassis with vibration‑damping insulators.

Specifications verified from STAX official sources and the owner’s manual.

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Professional Recognition

• Reviews

  • What Hi‑Fi? on SR‑009S with SRM‑700S: “The total lack of background noise, combined with the super‑clean, distortion‑free sound quality…” A reference‑grade, effortlessly revealing pairing.
  • SoundStage! Australia: notes the dual 5‑pin outputs, high gain, and “huge amplification” with very low noise—highlighting the SRM‑700S’s composure on challenging material.

• Heritage
  STAX pioneered the “earspeaker” concept and continues to design and manufacture in Japan—“The Founder of Earspeaker – Since 1938 –.”

• Innovation
  First STAX driver to employ a J‑FET second stage, combined with hand‑selected FETs, EMI‑shielded volume, and WIMA film capacitors for stability and clarity.

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The Bottom Line

If you want a neutral, hyper‑resolving, and whisper‑quiet window into your recordings, the SRM‑700S delivers. Its all‑FET design, dual PRO outputs, and smart system integration features make it the solid‑state energizer to anchor a modern electrostatic setup—confidently, cleanly, and for the long haul.

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Notes for buyers

• Compatibility: Designed for STAX PRO‑bias (580 V, 5‑pin) earspeakers such as SR‑X9000, SR‑009S, and SR‑007 MK2. Not compatible with older 6‑pin Normal‑bias models.
• System setup: Use “External (Bypass)” mode when feeding the SRM‑700S from a preamp; use “Internal” for direct line‑level sources. Observe ventilation clearance as per the manual.

This research‑backed description is based on the official STAX specification pages and owner’s manual, complemented by respected professional reviews for listening context and user‑facing features.