Just assembled my first nice headphone/amp/DAC rig. The cans are Beyerdynamic DT-770 600 ohms, amp is a Ming Da MC 84 C07 and a Cambridge DACMagic. The amp uses two 12AX7 preamp tubes, two EL84 power tubes and a 6HU6 magic eye tube. The sound is amazing, but not like anything I've ever heard from a 2-channel system. The highs are very crisp and bass is excellent too. Rolling 12AX7 tubes makes a big difference in the sonics also. Am currently trying some select (red tip) Telefunken 12AX7s purchased locally from MCAudioarts on eBay.