Until this moment, until 2017 January 12 around 9PM, want to know what my most recommended portable battery-powered headphone amplifier was? I’ll tell you. It was Vorzüge’s PURE II (both versions). I can get it to eat up an overdriven Chord Mojo signal of 122dB and spit back around 120dB. At stable volumes, it measures between 118-119dB. It is an amazing amp whose load stability, signal to noise ratio, THD, IMD, and dynamic range are matched by almost no one.