Unfortunately, Sovteks. Some Tungsrams maybe - they sound better, but who knows about longevity. The Modulus eats tubes, has very high gain, and most of the really nice NOS tubes just wont last. Upscale Audio has some NOS Sovteks that he says are better than the new ones. I bought some awhile back and they're ok, but I cant remember what the originals sounded like before they wore out so to make any comparison.
