I'm always willing to try new tubes, just for fun! Read the mention by PB in other topics about the 76 and 37 later developing into 6sn7/12au7. So I've order a box of 76 and 37 tubes to try in my Crack.
Anyone tried these yet? I'm a bit worried about the operating points not being optimal with Crack.
I use ECC82 -> 6J5 and bought a 6J5-> 76/37 adapter.