Grid leak resistor wattage

[Stu Lyon]

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


----- Original Message -----
From: "Brian Wood" <brianmwood at DIRECWAY.COM>
To: <HEATH at LISTSERV.TEMPE.GOV>
Sent: Tuesday, November 12, 2002 6:03 PM
Subject: Grid leak resistor wattage


> How much current comes out of a 12AX7's control grid? Everyone's said to
> replace the grid leak resistor on the DX-100's audio input stage with a
10M
> resistor to better match my D-104. But the current better be darn close to
> zero or I'm gonna need a big wattage resistor! Even 1 mA would require a
10W
> resistor. It's a 1/2W 470K now. I happen to have a 1/4W or maybe it's an
> 1/8W 10M resistor. Help!
>
> Brian, W0DZ
>

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