Been doing a lot of research on power tubes lately, have ordered a wide selection of tubes including 7236 5998 and rca6as7gs.think they’re all going to arrive before my amp does though!! Looking at input tubes now, am being confused by the numbering systems. Can the amp take 6sn7 variants? What’s the difference from the 6SJ7? Any recommendations aside from rca 5693, EF80/86 and Sylvania 6sj7 mentioned in thread?