STAX SRM-400S

The New STAX SRM-400S: The Mid-Range Semiconductor Driver, Reimagined

STAX introduces the SRM-400S, the successor to the SRM-353X, a newly developed semiconductor driver unit designed for discerning audio enthusiasts. The SRM-400S features custom, low-noise dual FETs in both the input and output stages, ensuring high-quality sound reproduction. These FETs are specifically selected and tuned, similar to those found in the high-end SRM-700S model, delivering exceptional audio performance.

The SRM-400S incorporates an additional transformer specifically for the low-voltage winding, enhancing energy efficiency while also improving sound and performance. The reinforced, non-magnetic aluminum chassis is designed to resist external disturbances like vibrations, creating an optimal acoustic environment.

The unit includes RCA and XLR inputs, the signature dual concentric volume control from STAX, and an RCA parallel output. All electronic components have been chosen to ensure an eco-friendly and acoustically optimized configuration. The fully DC-coupled amplifier design, which avoids coupling capacitors in the signal paths, preserves the pure sound—a traditional hallmark of STAX.

With its high-resolution sound, characteristic of semiconductor amplifier circuits, and dynamic bass response, the SRM-400S offers balanced audio performance across all frequencies. It is ideally suited for use with the Lambda series but also serves as an excellent upgrade from entry-level models like the SRS-3100. The SRM-400S is an ideal choice for both beginners and advanced users among STAX's updated driver units.

Technical Specifications of the STAX SRM-400S

• Type: DC amplifier unit with FET configuration in all stages
• Frequency Response: DC to 90kHz (with an SR-L500 MK2)
• Gain: 60 dB
• Harmonic Distortion: ≤ 0.01% (at 1kHz/100Vrms output)
• Input Impedance: 50kΩ (RCA), 50kΩ x 2 (XLR)
• Maximum Output Voltage: 400Vrms (at 1kHz)
• Bias Voltage: DC 580V
• Operating Temperature/Humidity: 0 to 35 °C / under 90% (non-condensing)
• Inputs: RCA x 1, XLR x 1 (mutually exclusive input)
• Output: RCA parallel output
• Power Consumption: 30W
• Dimensions: 195 mm (W) x 102 mm (H) x 376 mm (D) (including protruding parts)
• Weight: 3.4 kg

The SRM-400S sets a new benchmark for mid-range semiconductor driver units, offering powerful sound reproduction and excellent performance suitable for serious audiophiles.