>Is it really necessary to have operating bias on 811A's ?
Depends on anode supply V. What is necessary for linear operation with
thoriated-tungsten cathodes is a Zero Signal Anode Current (ZSAC) of c.
20% of maximum-signal anode current.
>If so, is 4.5
>to 5 volts a good value ? Can a string of 2 to 3 amp rectifier diodes be
>used instead of a Zener ?
Yes and zeners are not adjustable in 0.7v steps.
> I am currently using a 47 ohm resistor from
>grid to ground on each tube (4) and am not sure this the right way to go
>about it.
It's good if the grid is bypassed for RF with a total of c. 1000pF using
two, different vakues of C. A 47-ohm, 1/4w or 1/2w resistor will carry
normal grid current, but it will usually open during a glitch that might
damage the tube.
cheerz, Ed
- Rich..., 805.386.3734, www.vcnet.com/measures.
|