STAX SRM-400S

STAX introduces a new phono preamplifier, the SRM-400S, the successor model to the SRM-353X. The custom low-noise STAX DUAL FET is installed on the first stage. And FET is also installed on the Last Stage. The characteristics of the right FET and left FET are strictly measured. The selected FETs are installed just like in the SRM-700S. The SRM-400S succeeds the design and manufacturing method of the high-end model SRM-700S.

In addition to the conventional power transformer for the high-voltage circuit, the newly designed power transformer with winding for the low-voltage circuit is installed in the SRM-400S. The low-voltage winding improves energy efficiency and achieves additional energy savings and better sound quality than conventional drive units such as the SRM-353X.

The new chassis, more rigid than the conventional model, is installed. The chassis has a hybrid structure using a lot of non-magnetic aluminum and further reduces the effect of environmental noise factors such as vibrations. The inputs are RCA and XLR, mutually exclusive inputs. The custom concentric double volume knob common to STAX products and the RCA PARALLEL OUT functions are installed in the same way as conventional drive units. All electrical components are strictly selected with consideration for the environment. Sound quality and performance are also improved. The complete DC amplifier configuration in which the signal circuit does not include any coupling capacitors is one of the greatest traditional features.

The SRM-400S supports high-resolution sound that is unique to the semiconductor circuit and dynamic reproduction of low-range sound. Simultaneously, a better sound balance is sought compared to the SRM-353X. From the low range to the high range, the sound of each range is well harmonized. Not only for combination with the advanced lambda series, the SRM-400S is also ideal for upgrading from the entry-level SRS-3100. It is the promising new model that covers beginners to intermediates among the renewed range of drive units.

Technical Specifications

Electrical Specifications

• Architecture: direct current (DC), dual field-effect transistor (FET) input stage, field-effect transistor (FET) output stage
• Frequency response: direct current (DC) - 90 kHz
• Gain: 60 dB
• Total harmonic distortion (THD): 0.01% (1 kHz / 100 V)
• Maximum output voltage: 400 V RMS
• Bias voltage: 580 V DC

Impedances and Connectivity

• Input impedance:
  • RCA jack: 50 kΩ
  • XLR jack: 100 kΩ
• Inputs: XLR jacks, RCA jacks
• Outputs: 2 electrostatic headphone outputs, RCA jacks

Physical Characteristics

• Dimensions (W × H × D): 195 × 102 × 376 mm
• Weight: 3.4 kg
• Operating temperature: 0 to 35 °C
• Power consumption: 30 W