Peter
I don't think the problem is with the output's, the 6jn6 tubes. Generally, a problem as you are describing is in the input/driver circuit, not the output circuit. I would try the inputs first, the tube complement recommended above.
So far as the cryoed 6jn6 output tubes go, try to get in touch with Allan Bghan at the e-mail link above and see if he even has a set of them on hand. I'm not sure that he does but he is talking about producing another batch, mucho inquiries. These tubes are all individually tested prior to the cryo treatment. So he is using the creme de le creme before the process. They are probably a lot better tubes to start with than Berning uses. Twl's point in his first post is a good one and true. The cryoed tubes are well worth it and you might want to just get both the inputs and outputs. If neither of these upgrades turn out to be the problem you still aren't throwing away your money, believe me. You can be assured that there is a system synergy problem but when you find it, your zh270 will be ready and waiting :)
I don't think the problem is with the output's, the 6jn6 tubes. Generally, a problem as you are describing is in the input/driver circuit, not the output circuit. I would try the inputs first, the tube complement recommended above.
So far as the cryoed 6jn6 output tubes go, try to get in touch with Allan Bghan at the e-mail link above and see if he even has a set of them on hand. I'm not sure that he does but he is talking about producing another batch, mucho inquiries. These tubes are all individually tested prior to the cryo treatment. So he is using the creme de le creme before the process. They are probably a lot better tubes to start with than Berning uses. Twl's point in his first post is a good one and true. The cryoed tubes are well worth it and you might want to just get both the inputs and outputs. If neither of these upgrades turn out to be the problem you still aren't throwing away your money, believe me. You can be assured that there is a system synergy problem but when you find it, your zh270 will be ready and waiting :)