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In Reply to: RE: Yep (nt) posted by Lew on May 11, 2016 at 13:17:07
"The increase in impedance with rising frequency is compatible with the rationale behind using a grid-stopper in the first place."
In many tubes the grid will oscillate with nothing connected to it at all. It must be anchored or dampened with a lo-Z connection to prevent that. Inserting an inductor allows the grid to "wiggle" as the frequency increases and will promote oscillation.
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Buy Chinese. Bury freedom.
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Wouldn't the resistive component of a helical resistance element entirely swamp the inductive component above 100 ohms or so?
"Wouldn't the resistive component of a helical resistance element entirely swamp the inductive component"
A more important question is whether it will swamp the oscillation. Some tubes will oscillate even when the grid is grounded. The 811A is an example of this. Other tubes have a grid structure whose internal inductance needs only the tiniest amount of additional, external inductance to set them off. In the context of your question, each amplifier would need to be approached on a case by case basis if the goal is indeed to determine what the designer can "get away with." I don't have time for that, so I use carbon comp. It's not clear to me why anyone would use anything else for this purpose. There's no downside.
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Buy Chinese. Bury freedom.
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