A lot of different 6sn7 combos. Havent messed with the kt77/6l6 to much. I can make it fast, extended in both directions, and ss sounding or I can make it slow, warm and rolled. I cant seen to find that magic combo of fast, warm and a little rolled. Oh well, I will be running it with some kt77 this meet and some different 6sn7 to get some impressions. Havent spent as much time listening due to ear aches and the release of the ps4 and xbox1.