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How much peak voltage can an EL34's control grid take? I've got this
weird motorboating going on in my guitar amp, then I realized the
output tubes were clicking, and arcing was visible inside one. The
EL34 control grids might be getting as much as 450v (!), which is the
value of the plate supply feeding the 12AX7 stages before the EL34.
The amp is very simple: 2 typical 12AX7 gain stages, one 12AX7 cathode-
coupled phase splitter, then the EL34s in push-pull, transformer
coupled output. I'm wondering whether it's a bad tube, or I'm
exceeding maximum values.

Thanks!

Sean B