@brighamdoc The KT120s and 150s had been in the amp for about 3 weeks listening about 3 hours a night. Maybe not enough to really be "burnt in". I may have to give each another month of listening. I've heard the KT150s can take months to really shine. They did sound good in the system so it would be interesting to see.
Yep. When I first purchased my last pairs of tube mono amps which run KT150s or KT120s, I kept going back and forth comparing the sound to my local dealer, same amps. He had 300-400 hours on his demos, I had 40,80, 100 on mine. Not the same. Breaking in, wearing out, smoothing out, whatever you want to think about it - both quads of these sounded nicer after 200-300 hours on them fwiw. As the time goes on and highs round off just a tad with wear, the midrange and body comes in more, also a little more euphoric now too - from my experience with them. The difference is noticeable even with the most primitive listening to my FM tuner or CDs or high-res streaming. Not all agree but some good time on them can help change the sound. Wether you like the changes or not is up to you.