Mattnshilp, I admire your effort, but so much is very fragile with everything these days. Or you comparing the units all in exactly the sale location, with the same wiring and ac plugs, and on the same isolation.
I have found the location of feet under a unit make a big difference, that some units work well with cables that another hates, that some cables, most obviously the High Fidelity cables hate to be moved at all and take a long time to recover.
Long ago, I participated in a great double blind testing of many preamps with many of their designers present and voting. This was well before cables were much in fancy as well as before much was done about isolation. We rated each and went on to the next. At the end the Bozak was the winner??? I borrowed one and took it to my home. It was awful! I lost confidence in even well done double blinds, much less the worthless 30 second, same or different crap.
I have found the location of feet under a unit make a big difference, that some units work well with cables that another hates, that some cables, most obviously the High Fidelity cables hate to be moved at all and take a long time to recover.
Long ago, I participated in a great double blind testing of many preamps with many of their designers present and voting. This was well before cables were much in fancy as well as before much was done about isolation. We rated each and went on to the next. At the end the Bozak was the winner??? I borrowed one and took it to my home. It was awful! I lost confidence in even well done double blinds, much less the worthless 30 second, same or different crap.