Here we go... https://diyaudiostore.com/products/korg-nutube So it IS a tube but just build differently than traditional vacuum tubes. Interesting. But of course the aren't going to tell you how long they last and i scanned the page and saw nothing about that. At $50 a pop they better last tho ! They are low voltage and don't even heat up to the point of glowing so that in itself should contribute to lifespan.