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Old 3rd December 2002, 06:32 PM   #1
Joel is offline Joel  United States
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Default change to grid choke?

Anyone have any experience changing the power tube's grid resistor to a choke?
Is there measurable improvement in performance?
Hammond has a 150H, 8mA model. It's only $19, so not much of a risk I suppose.
(tube is the 71A from my SE amp posted before)
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Old 5th December 2002, 03:07 PM   #2
Joel is offline Joel  United States
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I'll reply to my own post!

With a plate resistance in the previous stage of 10k ohms, using 2PiFL, the reactance of the choke at 20Hz will be 18,849.6 ohms... so, since 10,000 would be the half power/3dB down point, I will be under that amount at 20Hz. This is pretty good.
And of course at 20kHz, the reactance will be 18,849,600 ohms... no loss at the high end.
How's my math?

So, I think it should work out good.
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Old 5th December 2002, 03:20 PM   #3
dhaen is offline dhaen  Europe
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Sorry Joel, no practical experience on that. They've banned the most prolific poster who could have given an answer - with his own personal charisma of course...
Theoretically.... there could be some xtra power in the bag, just as the grid is driven slightly positive. Also you might get away with a smaller coupling cap; but beware of resonance
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