Starting into tests with the HA1, here are some notes with HD800 SE cans.
Did the following comparisons:
PC ( JRiver19 ) > USB2 > HA1 > SE to HD800
PC ( JRiver19 ) > USB2 > Mytek Stereo 192 DAC > Balanced> Audio-gd Master 8 > SE to HD800
HA-1 settings– Set gain to High
Mytek DAC – Volume bypass, analog output gain jumpered to low; Master 8, gain at Low, power on High
HA1 gain must be set to High with HD800 SE to get to acceptable listening levels (HA1 low gain max 69dB, HA1 high gain max 84dB with pink noise). At high gain noise floor is still very low (good) and is loud enough for normal listening.
At lower volumes with gain=high, drove the HD800 acceptably. At very high volumes imaging and depth slightly worse than Mytek \master 8 combo. Bass response was clean, good in both combos but not awe inspiring in either.
The HD800 is a clinical and revealing can and the HA1 did not mellow out any of these tendencies. The combo was very unforgiving of bad recordings, I was wincing in a few places. Signature was to my ears very similar to the Mytek \ audio-gd combo. In my opinion, the HA1 is not a good match for the HD800 unless you’re interested in dissecting your recordings at a lower volume. Definitely not a rock out combo.