Hi:
I try once before, use GE NOS 6L6 replace EH 6V6, wanderful,
but frist , the normal working vola for 6V6 is 400V, for 6L6 is 300L(these GE are selected, can stand 450Val),
and they are too expensive(dealer tell me that he bought them at US$100/matched pair 10 years ago, now should be at least US$200/pair), maybe u can try Groove tubes 6L6 (it is new release GE 6L6), about U$S80/pair, not cheap, and not know whether it can stand 400 Val or not