I received my HE5 and EF5 on Monday, 12/14. I have been feeding the combo music using an old Philips DVD player since and they have logged a tad over 255 hours in addition to the 20 hours of burn-in at the factory in China. During the 255 I fed different types of music and I varied the volume from very low listening to about Noon on the volume control (could be heard across room and sometimes in the living room). I did listen to them on and off during the burn-in and there was change (small as compare to other headphones) from start to finish but I found it very hard to hear any difference from day to day. Today I moved the unit to the main rack and it is being fed apple lossless files from my Dell PC using a Chaintech AV710 via an optical cable from Blue Jean Cable. The DAC is a Monarchy NM24 powered via a Monarchy Audio AC Re-generator and the IC are SILVER SONIC BL-1 I got on sale from Moon Audio via Audiogon.
The headphone is indeed very comfortable and the EF5 in low gain has plenty of power to drive the HE5. I find I have the volume at about 8 o'clock and that is plenty loud for me. Before I get into the sound I will describe a couple of minor issues I have with the rig.
1. The single ended cable is too short, IMO it should be at least 3 meters long. I have spoken about this with Fang and he indicated that after the Chinese new year they will be offering a longer cable and a balanced one. If this becomes a reality it will be a nice additions. BTW the stock cable is flexible enough and I like the red dot on the termination (headphone end) to help old farts like me with poor eyesight.
2. The hard plastic feet used on both the amp and psu are abysmal. The amp is way to close to the surface below and it transfers a lot of heat, plus by not having an air space the amp retains some of the heat instead of getting read of it. I would suggest placing rubber feet which provide at least a 1/2" or 5/8" of air gap. Besides a rubber feet will assist in preventing the amp from sliding when you attempt to insert the 1/4" plug.
3. Place small rubber grommets on all of the 4 screws on the plexiglass cover. This grommets would create an air gap which would assist in ventilating the amp, which like the EF1 gets quite warm.
4. Ditch the "tube protection" it IMO detracts from the amp, makes swapping tubes harder than it should, and retains heat.
As you can see in ergonomics my four "issues" are quite minimal and with the exception of the longer cable are quite easy to DIY a solution.
For sound impressions I will adding them to this thread as time goes on. It will not be a review but more of thoughts and ideas as a result of the music (mostly jazz) I listen too. For now I can say:
1. I do not hear any shrillness metallic sound in the top end as some have reported. It is energetic and it has a great extension but what I hear is clean and detailed. BTW, being 51 YO may be the reason I do not hear some of the treble issues reported by the younger listeners.
2. Bass is strong and like the treble it extends low. The low mids are very detailed as well and I do not hear any muddiness.
3. The mids are clear with long decay to the notes. Very easy to hear when a note starts/ends, the hi-hat sounds fantastic like it is being played in front of you.
4. I find the overall sound very life like with a fast presentation.
Based on the four bullets above you may think I really like the combo. The truth is the jury is still out. For some reason I do not find the combo as involving as the K501, RS-1, or the MarkL modded Denons. The individual elements of the presentation are extremely good, yet the sum of the parts do not bring to my face the smile the other cans do. Perhaps additional burn-in is needed, or I need to get used to their presentation.
I do want to like the combo because at times I can hear great sounds from it. But if it remain un-involving then I will have to re-think if I keep them or not. On a side note my wife who has excellent hearing really liked the combo and preferred to the MarkL modded Denons. More to come after I log another 50 to 150 hours of additional burn-in.