Plate voltage,and amperage is different. Go with the factory specs. If they offered a variety of tubes it would say so. It may work with a different tube But for how long.
I don't think that's a very good idea. Different tubes and different operating points. Will it blow up? No it should be okay. But I think you should stick with one of the 12at7 variants. There are some nice tubes available in the ECC81 family. Just my two cents.
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