I paired it with a DX3Pro as a DAC, using this as an headphone amplifier only and with the HD 6xx, it does wonder. I cannot let the music and go to sleep.
Firestorm7Update in January 2020: I was sceptic to change the good EH tube...but OH my, what a pleasant surprise: the new tube (https://www.thetubestore.com/6h23n-eb-6922) enhance everything...and my HD 6xx have now bass and sub-bass - wow!
I'm just a novice and it is the first tube a change...but I'm a ...seeker ..and karma slapped me in the face with positive reward!
I didn't knew what this amp can!