I've just been in such a nice place listening to HiFiMAN EF-6, HE-6, and Metrum HEX, that I just had to scribble something about it. The fashion in which these pieces of gear compliment each other makes it hard to write. In fact, I turned off my email, lowered the lights, and surrendered to the idea, that the world can go to hell for a while, if only for the sake of a few tunes.
LIstening to the Back Cello Suites as played my Rostropovich leaves the scent of rosin in the air. I half expect Mtislov to stop between songs and motion to me for a glass of water. Of course this is no small shakes of a system. I recognize the laws of diminishing returns as they pervade audio...but the extra scratch, to me, in the best of cases, is all about picking up that sense of ease. All the information, without any of the strain that comes with reproduction. This combo takes big healthy spoonfuls of ease and ladles them right at your ears. Perhaps the advantage of having components that were engineer matched during voicing. Never have I heard so much more squeezed from the HE-6. I just wish I had binding posts on the back of my EF-6, so that I might cause even more trouble.
I've not heard the bass delineated so well on my Keb Mo sides as with this combo...bass is something you really gain in an unexpected fashion from pairing the EF-6 and the HE-6. The HiFiMAN EF-6 is a behemoth as headfi amps go, and with it's size comes refinement of the experience...and they'll drive just about anything. Marvin's calling.
Back to listening. All the best...