STAX SRM-700S Driver Unit – Product Description

The STAX SRM-700S is an all-semiconductor driver unit that employs custom low-noise dual FETs in the input stage, and for the first time in STAX’s history, J-FETs in the second amplification stage. It follows STAX's traditional DC amplifier structure, avoiding coupling capacitors from input to output. While sharing many design features with the SRM-700T, including the low-noise dual FET input stage and chassis layout, the SRM-700S uniquely introduces dual FETs in the second stage as well.

The output stage, using emitter-follower circuits capable of supplying large current, along with low-noise J-FETs, enables powerful and stable drive even with high-frequency-rich sources. This circuit design achieves outstanding clarity, quick transients, dynamic impact, and scale, delivering sound that is rich in detail and realism—a hallmark of semiconductor amplification.

Perfect for users who wish to experience the same purity and intricacy of music as heard by musicians and recording engineers in the studio.

Key Features

• Symmetrical Main Circuit Board Design: Features a large central heatsink and fully symmetrical layout for optimal heat dispersion and signal integrity.

• Custom Low-Noise Dual FETs: Both the first and second amplification stages use hand-matched, low-noise dual FETs for minimal distortion and precision amplification.

• High-Grade Film Capacitors: Premium WIMA film capacitors are used in key areas. No coupling capacitors are used in the signal path for pure DC amplification.

• Shielded Volume Control Unit: Includes a traditional STAX dual-axis, four-gang volume control housed in a shielded enclosure to eliminate external noise interference—same as in the flagship SRM-T8000.

• Input Terminals: Equipped with RCA line input and parallel output, as well as an XLR input selectable via rear panel rotary switch.

• EXTERNAL (BYPASS) Mode: Allows bypassing the internal volume control for use with a source’s own volume control or an external attenuator—ideal for use as a dedicated power amplifier for earspeakers.

• High-Grip Aluminum Insulators: Newly developed large aluminum insulators with high-friction material ensure stability even when plugging in headphones.

Rear Panel Overview

Provides access to RCA and XLR inputs, rotary input selector switch, parallel output terminal, and level control mode switch.

Specifications

• Type: All-FET DC amplifier configuration driver unit

• Frequency Response: DC to 100kHz (with 1x SR-009S)

• Gain: 60dB

• THD: Less than 0.01% (1kHz, 100Vr.m.s. output)

• Input Impedance: 50kΩ (RCA), 50kΩ x2 (XLR)

• Maximum Output Voltage: 450Vr.m.s. (1kHz)

• Bias Voltage: PRO 580V

• Operating Temperature/Humidity: 0–35°C / ≤90% RH (non-condensing)

• Inputs: 1x RCA, 1x XLR

• Output: 1x RCA parallel output

• Power Consumption: 46W

• Dimensions: 240mm (W) x 103mm (H) x 393mm (D) (including protrusions)

• Weight: 6.3kg

• Country of Origin: Japan