After reading through the
Audiokarma thread on the E6, I ordered the Soviet tubes off of Ebay and a pipe cutter off of Amazon that can accommodate 1.25” diameter. I just had to mark the new tubes with a marker before I cut them out so that I could easily orient them into the sockets. The Youtube video below shows another method to cut the shells. Truthfully, I was happy with the Chinese tubes that came with mine; I think I got lucky. Initially, they had obvious bass roll-off, but that went away after a couple of days. To me, the most obvious difference with the Soviet tubes was that they didn’t have that initial bass roll-off. There were reports that the Soviet tubes were less likely to be microphonic, but I never had those issues with the stock tubes.