Are you able to give a direct comparison with phoenix? Since you are selling them all. Otherwise I would appreciate if you could PM your opinion to me.
Source is a Reference 7.1 and NFB8.1 running acss and balanced connections. As a comparison the Phoenix headphone amp appears to be about the same volume level on a volume setting of 30 as the Master 6 is on 25 (with the volume set to 99 steps on both). This is on both the balanced akg702s and balanced HD800s.
I am suprised so few people have fedback their opinions on sound quality. I cant because I am an Audio-gd reseller in New Zealand.
Hope this is helpful.