Tubes and headphones are a match made in heaven. So much so, we're certain Walter White never would've gone down a dark path if the "Breaking Bad" protagonist had Glass FX at his disposal. Yes, this Jolida unit is packed with science. But it's the tube headphone amplifier's warm sound and spirit-lifting emotionalism that will soothe even the hardest-to-please listeners. Outfitted with a pair of 12AX7A vacuum tubes, ALPS potentiometer, bass and loudness switches, Glass FX outputs a powerful 100mW.