First of all, I DID ask the manufacturer and never really got an answer, that's why I'm turning to you guys. When I bought my Victoria 20112, 7-10 years back, it came with an RCA/or Phillips 5Y3 in the rectifier slot. All the tubes were immediately replaced with RCA NOS everything, at the time. But I really want to try a GZ-34 in place of the 5Y3, even though mine is so old the tube chart doesn't say 5Y3/GZ34 on the tube chart inside of the amp cab. What's the real story on this? Can anybody help me? Thanks much.