But then we have the speakers, which could also have masked amp differences, and that seems to me more likely, if we are to believe there must be differences unperceived.
I was also thinking about the effect that the speakers could have had on masking any differences. Coincidentally my new Revel M105 also arrived today, so I re-randomized the cables and re-ran the test with the same set of tracks. I increased the volume by 5dB on Pre90 to -28dB gain and set it to 40 on Hegel. Their voltage output match within +/-10mV. I spent more time on certain tiny bits of each track (3-7 second segments) where I thought I would be more likely to hear a difference, going back and replaying much more often than the first time now that I got a hang of it.
1- Grimes | Vanessa | N
2- Nina Simone | Sinnerman | N
3- Air | Cherry Blossom Girl | N
4- Beethoven | Symphony No. 5, Carlos Kleiber Wiener Phil, Allegro con brio | N
5- Celeste | Tell me Something | N
6- Dire Straits | Money for Nothing | N
7- Moloko | The Time is Now |
L
8- Daft Punk | Give Life Back to Music | (had to skip*)
9- Michael Jackson | Billie Jean | (had to skip*)
10- Judas Priest | Pain Killer | N
* for some reason Roon was acting up on these two tracks (maybe because of their 88khz sample rate) and not letting me smoothly going back and forth, so I decided to skip them.
The only track where I did have a preference was Moloko's where the segment I repeatedly listened to was right at the beginning and I felt the left system had a tiny bit more ring to a couple of bass guitar notes. I tried this like 4-5 times and I was convinced there was a genuine difference. After that I revealed who's who and it turned out the L system was the Benchmark.
I then listened to that same segment several times with each amp with louder volume, but I am not very sure if the difference is even there when I do this sighted. I will re-randomize the cables tomorrow and recheck this track again in another blind test.