But with that said, we do need to mention one concern about the Stax/Woo system. When playing some relatively simple music, the Stax/Woo combination can sound somewhat stressed or shouty on vocals, especially female vocals. This suggests a frequency response elevation in the mid-range. Whether this is a Stax artifact or something created by the WES is not easy to say. This effect is less noticeable with other amplifiers, but that may simply mean that the WES is revealing—but making no attempt to compensate for—a small sonic error inherent to the SR-009s.
Philosophically, we note that all the electrostatic amp manufacturers in this top tier category seem to be aiming to build amps that could conceivably be used with any type or model of electrostatic headphone, rather than creating amps specifically matched to (or optimized for) the SR-009. In that sense, we think Woo’s approach has been to pursue accuracy and neutrality first, and then to the sonic “chips,” so to speak, fall where they may.
Given that the WES is quite good but not perfect, you will want to consider how the WES compares to other electrostatic headphone amps. While we haven’t completed our work on this, we would say that the Woo majors in clarity and dynamics, the Head Amp Blue Hawaii SE majors in harmonic richness and warmth, and the Cavalli Liquid Lightning falls somewhere in the middle.