Okay. Fact: AI sounds great but eats tubes. You have a choice best sounding vs. longest lasting. I've bought over 100 NOS tubes in the past 2-3 years. Best sounding in order (combinations of 7308 6922 & 6DJ8) Amperex, Telefunken, Seimens, Tungsram-some lasted less than 1 hour. I could hear a degradation even in Tungsram over months and they were the strongest. Longest lasting Sovtek 6H23, Telefunken PCC88(sounds surprisingly good, very good really & bought them for almost nothing)-have yet to burn any of these out yet. I've not rolled much recently and have left in now for 1 year at least E288CC. They sound great and appear to be indestructible. They cost alot. Note they're so tall the top of the case can only be reinstalled with spacers. Too expensive really. My advice, if all you want to do is enjoy music rather than enjoy tube testing, call Kevin Deal at Upscale Audio and get his best 6H23 for $25. If you turn off the unit between sessions like me they may outlive you.