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On Tue, 29 Nov 2016 06:37:46 -0500, gudguyham wrote:
>Don't forget a grid trip overload protection.
The 8877 has a grid dissipation rating of 25 watts. The actual
dissipation when driven to 1500 watts is about 2.5 watts. Unless you
are unusually careless, you don't need a grid protection circuit.
Remember the driving power of 40-60 watts in grounded grid is mostly
"fed through" to the output. There are tubes with extremely fragile
grids but the 8877 is not one of them.
A commercially built amp is different however. Since the maker has no
control over who is going to operate it, a grid protection circuit is
probably a good idea, but in a homebrew amp where the builder and
operator knows what he is doing, it is overkill IMO.
73, Bill W6WRT
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