STAX SRM-353X Electrostatic Headphone Amplifier, Wired, Silver

STAX SRM-353X Electrostatic Headphone Amplifier (Wired, Silver)

Hear your STAX come alive with effortless speed, air, and control

If you’ve fallen for the clarity of electrostatics but still hear a hint of glare, thinness, or congestion from lesser energizers, the SRM-353X is your antidote. This all‑solid‑state, pure Class‑A driver unit was engineered by STAX to unlock the signature microdetail, lightning‑fast transients, and holographic staging their earspeakers are famous for—without adding noise or smear. A balanced XLR input, direct‑coupled DC topology, and dual PRO‑bias outputs make it the perfect heart of a refined electrostatic system.

---

Why Audiophiles Choose This Product

• The sound: clean, fast, and open

  • Neutral, highly resolving presentation with excellent control top‑to‑bottom; a natural partner for Lambda‑series earspeakers like SR‑L500 Mk2 and SR‑L700. Community impressions often characterize the 353X as quicker and more controlled than tube alternatives, while tubes can sound sweeter—choose to taste.

• Purist Class‑A, DC‑coupled engineering

  • Original low‑noise dual FET input stage and an improved output follower run in pure Class‑A with no coupling capacitors in the signal path—preserving microdetail and transparency.

• Practical, system‑friendly design

  • Slim, non‑magnetic aluminum chassis; custom concentric 2‑axis/4‑gang volume control for precise channel balance; RCA “parallel out” to loop your source to another component.

• Plug‑and‑play compatibility

  • Dual STAX 5‑pin PRO‑bias outputs (580 V) drive modern STAX earspeakers; RCA and balanced XLR inputs integrate cleanly with DACs, streamers, and disc players.

• A modern STAX classic

  • Introduced in 2015 and celebrated enough to receive an 80th‑Anniversary limited “BK” edition, the SRM‑353X later set the benchmark for its successor, the SRM‑400S. That lineage tells you everything about its staying power.

---

What’s Included

• Main product: STAX SRM‑353X driver unit (electrostatic headphone amplifier), Silver finish; dual PRO‑bias 5‑pin outputs.
• Primary accessory: AC power cord (region‑specific).
• Secondary items: In many regions a basic RCA cable is supplied. Check your retailer for local inclusions.
• Documentation: Owner’s manual and warranty card (region/distributor dependent).

---

Technical Specifications

Specification	Value	Notes
Product Type	Wired	RCA or XLR line‑level input; STAX 5‑pin PRO‑bias headphone outputs.
Frequency Response	DC–90 kHz	With one SR‑L series earspeaker connected.
Gain	60 dB (×1000)	Ample voltage swing for modern STAX earspeakers.
THD	≤0.01% @ 1 kHz, 100 V RMS	Low distortion solid‑state Class‑A design.
Max Output Voltage	400 V RMS (1 kHz)	Supports high dynamic peaks cleanly.
Inputs	1×RCA, 1×XLR (mutually exclusive)	RCA “parallel out” pass‑through provided.
Headphone Outputs	2×STAX PRO‑bias (5‑pin)	580 V DC bias x2.
Input Impedance	50 kΩ (RCA); 50 kΩ ×2 (XLR)	Easy to drive from most sources.
Power Consumption	30 W	Pure Class‑A operation; allow brief warm‑up for best sound.
Dimensions	150 × 100 × 360 mm	W × H × D, incl. protrusions.
Weight	3.0 kg (≈6.6 lb)	Solid, resonance‑controlled build.
Chassis	Non‑magnetic aluminum alloy	Vibration‑ and interference‑resistant.
Finish	Silver	Model shown here.

---

Professional Recognition

• Reviews

  • HiFiReport found the SRM‑353X + SR‑L500 Mk2 combo to be one of STAX’s most balanced pairings for sound and value, recommending auditions against tube alternatives like the SRM‑006tS to match taste.
  • In Head‑Fi community comparisons, many listeners describe the SRM‑353X as faster, more neutral, and better controlled than tube counterparts, with tubes adding warmth—useful guidance for system voicing.

• Heritage

  • STAX has been refining electrostatic earspeakers and driver units for decades; the SRM‑353X launched in 2015, received a commemorative “BK” run in 2018, and its design informed the SRM‑400S successor—clear lineage from a storied brand.

• Engineering pedigree

  • The 353X’s direct‑coupled, all‑FET Class‑A architecture, balanced input option, and meticulous parts selection reflect STAX’s purist approach to preserving signal integrity.

---

The Bottom Line

If you want the clarity and speed electrostatics promise—without romance or haze—the SRM‑353X delivers a reference‑grade, neutral, and incisive drive that lets your STAX earspeakers perform at their peak. It integrates cleanly into modern systems via RCA or balanced XLR, provides dual PRO‑bias outputs for flexible listening, and embodies the engineering rigor that’s kept STAX atop the electrostatic category. For many listeners, it’s the solid‑state “sweet spot” in the STAX ecosystem—and a confident choice for building a revealing, enduring reference chain.

---

Notes and guidance

• This is an electrostatic driver unit (energizer), not a conventional dynamic/planar headphone amp. It works with STAX 5‑pin PRO‑bias earspeakers; do not use with “normal‑bias” 6‑pin vintage models.
• The SRM‑353X was followed by the SRM‑400S; many owners still value the 353X for its neutral, fast character. If you prefer a richer tube flavor, audition against the SRM‑006tS.

Sources used for verification: official STAX materials, retailer spec sheets, professional reviews, and community impressions. Key specs and features were cross‑referenced across multiple listings to ensure accuracy.