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In Reply to: NOS AS7s in MA-1s? posted by ACHiPo on July 23, 2021 at 11:38:07:
The 6AS7G is the only version worthy of experimentation IMO/IME. With any other type (6080 or 6AS7GA) I think you'll find reliability to really be a problem.
Even with the American 6AS7Gs, I recommend preconditioning for at least 4 days and 4 nights at a minimum. This helps reduce arcing issues, especially right after setup.
No amount of preconditioning will help a 6AS7GA. The 'A' version has a smaller heatsink for the control grid, which warps and arcs in the class A2 region in which we operate the power tubes.
As a general rule of thumb, if the tube does not have the ST-7 envelope (the taller 'Coke bottle' package) then it won't have the grid heatsink needed and will likely be failure prone.
We've done alright with the Chinese tubes but they too need about 4 days and nights of preconditioning. They have certain failure modes that the Russian 6H13C does not. So the Russian tube is the preferred tube insofar as reliability is concerned.
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Follow Ups
- Be careful of American 6AS7s - Ralph 12:20:10 08/09/21 (1)
- RE: Be careful of American 6AS7s - ACHiPo 12:33:11 08/09/21 (0)
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