Grid leak resistor wattage

[Brian Wood]

On the AM Window BB, W2ZE wrote: "You need to replace the input resistor
going to the grid of the mic amp to 10 Megohm's and bypass it with a 50 pF
cap. That will smoooooth out the response of a D-104. Crystal elements want
to see a much higher input resistance than dynamic elements."

My mic does not have an amp. Thanks for all the comments on the power
rating. I guess two more neurons worth of thinking would have told me all I
needed. Duh.

Brian, W0DZ

-----Original Message-----
From: Stu Lyon [mailto:slyon at pacificnet.net]
Sent: Wednesday, November 13, 2002 6:27 AM
To: Brian Wood; HEATH at LISTSERV.TEMPE.GOV
Subject: Re: Grid leak resistor wattage


Brian,
You should get zero current flow out of a 12AX7 grid -- unless the tube is
gassy. Then you would throw it away.

Where did this 10 Meg come from anyway.  Conventional wisdom states that 1/2
to 1 Meg load on a unamplified D104 is about optimum. If your mike has an
amplifier (which is actual just an impedance matcher) then it can drive low
values of load resistor. The 470K grid resistor in your DX100 seems about
right for an amplified or unamplified D104.

73, Stu W6CUX
Winnetka, CA
slyon at pacificnet.net

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