Re: Grid Leak Bias

Posted by Eli Duttman (A) on February 20, 2002 at 10:43:47

In Reply to: Re: Grid Leak Bias posted by pedroskova on February 20, 2002 at 06:17:58:

The remarks about distortion are correct when signal levels are substantial. The charge built up on the grid has to be large enough to stay negative throughout the entire voltage cycle for operation to be "linear". An AM envelope detector and phono stages are situations where the LOW signal level allows contact biased tubes to work well.

If the grid leak resistor was omitted, the tube would cut itself off quite quickly, as more and more electrons collide with the grid and the charge builds up. The idea is to establish a balance between electrons striking the grid and those going to ground via the grid leak resistor. 2.2 MOhms is the "classic" value in AM envelope detectors. It works well with all sorts of tubes, both triodes and pentodes. The value of the grid leak resistor that works "best" in any situation would have to be determined on the bench, but 2.2 MOhms is a good place to start.

Eli D.

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Follow Ups Full Thread

Topic - RIAA design dilemma, need your opinions. - JLH 10:46:57 02/19/02 (18)

Re: RIAA design dilemma, need your opinions. - Paul Joppa 11:40:44 02/22/02 (0)

Re: RIAA design dilemma, need your opinions. - Kurt Strain 13:20:45 02/19/02 (11)

Re: RIAA design dilemma, need your opinions. - Thorsten 16:13:33 02/19/02 (9)

Thanks for sharing that thought, Thorsten - Kurt Strain 18:40:03 02/19/02 (8)

I already modified my RIAA - Kurt Strain 08:34:02 02/20/02 (7)

Re: I already modified my RIAA - Thorsten 09:10:53 02/20/02 (6)

Re: I already modified my RIAA - Kurt Strain 10:35:12 02/20/02 (5)

Should I copy... - PÃ¤r 00:55:40 02/21/02 (2)

Re: Should I copy... - Kurt Strain 08:20:50 02/21/02 (1)

Re: Should I copy... - PÃ¤r 23:46:24 02/21/02 (0)

Re: I already modified my RIAA - Thorsten 11:22:35 02/20/02 (0)

Re: I already modified my RIAA - Eli Duttman 10:49:54 02/20/02 (0)

Re: RIAA design dilemma, need your opinions. - Kurt Strain 13:37:18 02/19/02 (0)

my opinion- for what it's worth. - j.l.guillebeau@att.net 12:13:35 02/19/02 (0)

Re: RIAA design dilemma, need your opinions. - Thorsten 11:06:15 02/19/02 (3)

Grid Leak Bias - Eli Duttman 11:57:39 02/19/02 (2)

Re: Grid Leak Bias - pedroskova 06:17:58 02/20/02 (1)

Re: Grid Leak Bias - Eli Duttman 10:43:47 02/20/02 (0)

Follow Ups

Re: Grid Leak Bias - Eli Duttman 10:43:47 02/20/02 (0)

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