I can easily accept that the TT sounds better, so I have no problem with your test result. But I can't concur with your assertion (yes, actually perception) that the preamp has made it more transparent. It may have made it more pleasing, pseudo-transparent – that's what I halfways experience myself when I use my Corda Symphony to drive my HD 800 instead of the Hugo alone. But each time I switch back to the direct connection it becomes clear to me that nothing is more accurate than the original. Two devices sonically so close to each other – as reported and as conceptional from the electronics – can't be judged with additional electronics components in the signal path of one of them. The result may have been the same with equal preconditions, but certainly with different characterizations – which would have been of interest for me.
Sorry for the rant!