Sharing my impressions of the No1.
I have used it with Focal Stellia, R70X & Sundara.
The amp is remarkably transparent & detailed. I was not expecting this level of clarity. Notes have a lot of precision and are not diffuse or blurred. Very nice indeed. In fact I will say it here, it is more detailed than my Burson Soloist 3XP. The timbre is very crisp & pleasant.
Despite the jump in the level of clarity, the harshness has not increased. That is a very good achievement and also intriguing.
The sonic background is very dark and quiet and I think that gives a sense of space to the sound. I heard more reverb in some tracks.
Its also a very powerful amplifier but with more volume the sound just gets bigger rather than harsh/shrill. This is indeed remarkable. Bass & punch are present in good degree depending on headphone.
I think HD800S, HE1000SE, HD600 will absolutely fly on this.