Do we know this for sure? Source?
Regardless, if you use xlr interconnects from source, the chain will be balanced from the dac through to the xlr output on the amp. Using rca from dac to amp breaks the balance from the dac, so the amp cannot balance it again. Of course, using single ended...
As far as I know only difference will be rca input will not be balanced, xlr will be balanced. So with xlr input you are preserving balance through the chain.
This opens up a can of worms that you can read forever and not really find a good answer, in my opinion. Some say balanced only...
The pot on my monoprice 887 is basically perfect. Except I had to put on a white sticker for the volume indicator. Annoying but not the worst thing given the price/performance ratio of this thing.
I may be wrong on this, but wouldn't the feed forward "correcting" amplification circuit in a thx amp cancel any distoration introduced by a tube preamp? In which case, you don't add anything from the tube preamp. It may be adding gain or not. It may be doing nothing at all.
I have searched...