STAX SRM-400S Electrostatic Headphone Amplifier

Stax SRM-400S – A Quality Electrostatic Earspeaker Amplifier!

This is my third Stax amplifier. Like my two previous Stax amps from 1982-1986 (SRM-1/Mk2 Pro, SRA-14S) that are still fully functional and in use today, the SRM-400S puts a smile on my face to see and hear “Made in Japan” quality workmanship continue in their current products. Worthy improvements are the larger volume control knob, addition of XLR balanced inputs and a second Pro-bias earspeaker output. I appreciate Stax continuing with the ganged left-right channel volume control to allow for correcting channel imbalance of the input signal or imbalance of the earspeaker drivers. As expected, the SRM-400S sound is neutral, and there is no discernible noise or distortion at zero to very high gain. There is no power-on or power-off pops/thumps from the earspeakers. The SRM-400S has plenty of gain to drive my Stax SR-Lambda Pro, SR-507, SR-L700 Mk2, and Hifiman Jade II earspeakers. Volume control setting between 10-12 o’clock position gave more than sufficient gain to drive and reveal the sound signatures of these earspeakers. The SRM-400S effortlessly brings music to my ears. Well done again Stax!

Good unit