Just browsing around some off the grid tubes, I came across the 13cw4 triode, 'NuVista' tube. Man, my head spins. Sure, I knew there were a bunch of tubes made back in the day, and yet, everywhere I turn there are these oddball little guys on each corner. Guess these are hi-mu tubes made for such applications as tuners. Question that I have is how usable are they for audio? Something says, not a bad choice.