Triode vs Ultralinear

First of all…Did I spell “Ultralinear” correctly..? Too lazy to go into the other room to look at my amp. I'm still getting used to and breaking in my new ARC 160s and I find myself very attracted to the sound of all my music in Triode mode as opposed to Ultralinear mode. more buttery - rounded - warmer mids with incredible detail in the image. Wider soundstage even at louder volumes. No fatigue or sharp corners. Mind you, it’s an incredible amp and partnered with the REF 6SE and a pair of SF Serafino’s, I’m sitting pretty… Can anyone explain to me what I’m hearing…? I’ve read a little about it but nothing that explains it very well. Thanks and happy new year…!