Has anyone replaced the 6C19 tube with a 5881 in a

I have a BAT VK32SE preamp and a VK55SE amplifier. The bass and lower mid range are excellent however the treble is very bright. I have replaced my favorite silver cables with copper and added tube dampers that has taken a little bit of the adge off the top end but still too bright. The amplifier sounds better playing through my Merdian 808 CD player and bypassing the preamp. The preamp has the option of changing the 6C19 tube with a 5881. I am not familiar with this tube but have read good comments about the Tung Sol type.