I heard my pair on the HA-1 with high DR classical at a show. The SQ was not bad at all ranking amongst the better headamps. But it is entirely possible to completely max out the volume with that kind of music, and I am not a loud volume listener. It did not seem to clip though, but still this limitation doesn't really make it a very feasible long term amp for the HE-6. I don't know what voltage the source was putting out. To give a frame of reference for example the V281 had a lot more volume mileage, but the HE-6s sounded dreadful and unrecognisable. Gain change did not help.