Hm.... this is definitely not "cable break-in". The measurements of tubes and solid states are like night and day so I am not sure if this is an issue.
Tubes vs Solid State and the guilty party
https://positive-feedback.com/reviews/hardware-reviews/pass-labs-xp-10-preamplifier/
For years the old saw of tube or solid state sound has worked its way into reviews. As amplification and preamplification have gotten better, that fissure is closing.
And the guilty party IS? It has been a long civil war, but the chasm has been narrowed. Brothers, sisters, mothers, fathers will soon be able to cross the line and be united.
Will it take "The Vanishing"? IS it where one will find the truth?