@toro3 I'm using a R2R NOS DAC, the sonnet morpheus, so I rarely if ever get listener fatigue.
These Zu's are great at exposing your equipment. Change something and you can hear it pretty easy. And like most of this hobby, synergy is a major key. My amps are 12wpc Class A Valvet E3 (I upgraded from the E2) and two single ended flea watt tube amps. beautiful combos with the Zu's. Along the lines of exposing... you aren't going to get a bad recording to sound great, but great recordings are what makes me love this hobby. beautiful immersion into the music, very lifelike.