my input to several recent posts below:
a) yes frank van alstine's abx comparator is quite a truth teller... excellent piece that serves its purpose spot on... like all of what frank makes
b) in my listening tests in my own system, the audio mirror, mhdt and even denafrips dacs sounded more natural, open and dimensional than the border patrol (not that the bp is not good, the others were somewhat better to my ears)
c) point b above being said, the differences are quite subtle and only upon direct comparison can one discern and be confident about the difference - that is another benefit of the ava abx unit - you can a/b knowing what's what, then you also a/b without knowing test yourself if you can reliably and consistent hear what you think you hear among two items