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In Reply to: RE: Cathode bypass capacitor posted by Tubenstein on July 26, 2014 at 06:29:04
If you use appropriate DHTs you can avoid the cathode bias cap by running the filament through the cathode resistor. With the extra current you end up with a small cathode resistor (like 10 to 50 ohms) with no need to bypass. Tubes often used with filament bias are 4P1L, 26, 01A, 10Y.
Follow Ups:
So you don't have a capacitor across the last node of your filament bias power supply?
The filament is buffered one side with a gyrator and the other side a ring of two CCS . I think that puts the last cap well clear of the signal path . Lots of SS though , but the things sound good :)
Al
The filament raw supply with choke input and large cap feeds a Rod Coleman regulator stage.
The last thing you do is out a current regulator like a TO3 317 or the LT1085 as the last thing, no cap afterward. On the other hand, having only a 10 to 50 ohm resistor does not generate hardly any feedback to cancel out with a cap.
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